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In spite of the well-established design and construction approaches of slag–cement–bentonite slurry walls, the materials deteriorate inevitably in contaminated land. The development of effective materials which are sustainable, resilient and self-healing over the lifetime of slurry walls becomes essential. This study, for the first time, adopts a styrene–ethylene/butylene–styrene (SEBS) polymer to modify slag–cement–bentonite materials to enhance mechanical and self-healing performance. The results show that the increase in SEBS dosage results in significantly increased strain at failure, indicating the enhanced ductility thanks to the modification by the deformable polymer. The increased ductility is beneficial as the slurry wall could deform to a greater extent without cracks. After the permeation of liquid paraffin, the SEBS exposed on the crack surface swells and seals the crack, with the post-healing permeability only slightly higher than the undamaged values, which exhibits good self-healing performance. Scanning electron microscopy and micro-computed tomography analyses innovatively reveal the good bonding and homogeneous distribution of SEBS in slag–cement–bentonite. SEBS acts as a binder to protect the slag–cement–bentonite sample from disintegration, and the swollen SEBS particles effectively seal and heal the cracks. These results demonstrate that the SEBS-modified slag–cement–bentonite could provide slurry walls with resilient mechanical properties and enhanced self-healing performance.

Soil pollution is one of the major threats to the environment and jeopardizes the provision of key soil ecosystem services. Vertical barriers, including slurry trench walls and walls constructed with soil mix technology, have been employed for decades to control groundwater flow and subsurface contaminant transport. This paper comprehensively reviewed and assessed the typical materials and mechanical and permeability properties of soil–bentonite, cement–bentonite and soil mix barriers, with the values of mix design and engineering properties summarized and compared. In addition, the damage and durability of barrier materials under mechanical, chemical, and environmental stresses were discussed. A number of landmark remediation projects were documented to demonstrate the effectiveness of the use of barrier systems. Recent research about crack-resistant and self-healing barrier materials incorporating polymers and minerals at Cambridge University and performance monitoring techniques were analyzed. Future work should focus on two main areas: the use of geophysical methods for non-destructive monitoring and the optimization of resilient barrier materials.

This paper performs an extensive literature survey and example investigation on the stabilisation of slurry wall trenches during the construction of diaphragm wall panel trenches, and the failure modes of slurry wall trench instability, the stability theoretical analysis models and methods, the slurry formation and its protection mechanism, the influence of related factors on slurry wall trench stabilisation, and other related problems are summarized and analyzed emphatically. And then, based on the limit equilibrium analysis method, the mechanical models of the overall stability and local stability of the trench wall are established, respectively, and the design method of slurry unit weight is derived to ensure the stability of the trench wall. Furthermore, an example application shows that the established slurry unit weight design method is reliable. At last, this paper also proposes the focus and direction for follow-up work, that is, to construct an accurate and effective theoretical analysis model of slurry wall trench instability considering the influence of multiple factors and the calculation method of the slurry cake and its mechanical or mathematical relationship with slurry quality.

The slurry trench has become increasingly common in underground engineering and the stability of a slurry trench has been an important design issue. Although many studies have focused on the overall stability of a slurry trench, few of that are related to its local stability. Based on the limit analysis, both two dimensional and three dimensional rotational failure mechanisms for the local failure of a slurry trench in a sandwiched weak layer are proposed, and the upper solutions of 2D and 3D safety factors for local failure mechanisms are derived to evaluate the stability of a slurry trench. Moreover, a numerical analysis combined with the strength reduction technique is performed to investigate the local stability and the local failure process of a slurry trench. The proposed analytical method is verified through the comparison with the results of FLAC3D. Finally, a parametric study on the influences of geometric and geologic parameters on the local stability of the slurry trench are investigated. The results show that the investigation on the local stability of a slurry trench is effective and reasonable, which can provide a reference for the engineers in the practical engineering.

Various types of trenchless methods are extensively used to create engineering barriers for the purpose of achieving relatively low hydraulic conductivity of the subsoil and hydrotechnical structures. The most commonly used technologies of the grouting curtain creating are the DSM (Deep Soil Mixing), WIPS (Vibro Injcted Thin Wall), low-pressure injection and jet-grouting. Vertical barriers are widely used in environmental control systems to restrict the lateral spreading of liquid or gaseous contaminants and for seepage control through and beneath a levees. The barrier walls are constructed in a single or two phases using a slurry composed mainly of bentonite, cementitious materials and water. Often to solve complex geotechnical problems the technologies are combined (e.g. combining DSM and jet grouting). In the paper some examples of practical application of chosen types of technology dedicated different problems solving are presented. The results of geotechnical investigations of hydraulic permeability, shear strength and depth control of cut-off wall are given. The tests were carried out using BAT system, Cone Penetration Tests (CPT) and drillings. The presented test results should help define the technical and financial criteria that should be used to compare grouting based methods and other techniques applicable to the same geotechnical special works. These recommendations should permit an adequate application of grouting techniques and contribute to finding solutions for the delicate problem of ground sealing, notably when proceeding with hydrotechnical or environmental structures placed below water table.

Despite the common use of slag-cement-bentonite slurry trench walls for geotechnical and geoenvironmental applications, the materials deteriorate under mechanical, chemical and environmental stresses. Providing the slurry wall with the capacity of self-healing cracks, could address the concerns. This study proposes and investigates, for the first time, the self-healing slag-cement-bentonite incorporating reactive MgO pellets. The incorporation of the MgO pellets slightly increased the UCS and stiffness, without any significant adverse effects on the engineering properties of the slurry wall material. The crack closure percentages after hydration and carbonation reached over 50% and 80%, when the MgO pellets were added at a dosage of 5% and 10%. The post-healing permeability was as low as 8.4×10-9 m/s, satisfying the requirement for slurry walls. TGA and SEM-EDX results show that brucite and hydrated magnesium carbonates produced by the hydration and carbonation processes are the main healing products in the MgO-containing specimens. The uniform dispersion of MgO pellets and healing products was confirmed by micro-CT analysis, and it was observed most of the cracks could be at least partly blocked. The results have collectively demonstrated the great potential of reactive MgO pellets as an effective self-healing agent for the development of more reliable and resilient slag-cement-bentonite slurry walls.

The containment of contaminant plumes to protect groundwater from pollution is recognized as a frequent need in brownfield redevelopment. Plume containment can be physical, with slurry walls, jet grouting etc., or hydraulic, with wells capturing the subsurface flow that crosses the contaminated front (Pump &amp, Treat), or a combination of both types. The choice of the most suitable technique is a difficult task, since various aspects must be taken into consideration. In this paper, we present a framework for evaluating barriers in terms of effectiveness and efficiency, along with a simplified approach for the evaluation of capital and operational costs. The contaminant mass discharge escaping from the containment system is a robust indicator of its effectiveness, and can be derived from modelling results. The abstracted water flowrate is a key indicator of the efficiency and sustainability of each option, especially in the long term. The methodology is tested in a simplified case study and in a real one, highlighting the relevance of modelling results in guiding the choice and design of contaminant source containment systems.

The consolidation properties of soil-bentonite (SB) backfills containing 20% of the weight of sodium-hexametaphosphate-modified calcium bentonite (SHMP-20CaB) and prepared with 0 mM to 1000 mM calcium chloride (CaCl2) solution were evaluated. The results indicated that both consolidation stress and CaCl2 concentration had significant effects on the consolidation behaviors of the SHMP-20CaB backfill. In general, an increase in consolidation stress resulted in a decrease in the void ratio (e) and in the coefficient of volume change (mv), alongside an increase in the coefficient of consolidation (cv). The increased CaCl2 concentration yielded a dropped void ratio, and a nonlinear decreased compression index (Cc) and rebound index (Cs), respectively, from 0.18 to 0.13 and from 0.022 to 0.010, and a nonlinear increase cv. A threshold CaCl2 concentration of 100 mM was observed at the inflection points of the Cc, Cs, and cv. In contrast, the mv was insensitive to the CaCl2 solutions. The deterioration in e, Cc, and Cs and the increase in cv were the result of a compressed diffuse double layer of the bentonite by the CaCl2 solution, which thus exerted certain negative effects on the consolidation behaviors of the SHMP-20CaB backfill.

Hydraulic conductivity of sand-bentonite (SB) backfills amended with polyanionic cellulose (PAC) to lead nitrate (Pb(NO3)2) solutions was evaluated experimentally in this study. PAC-amended sand-bentonite (PSB) backfills were synthesized by mixing sand-bentonite mixture with 0.3 to 1.2% dry PAC (by total dry mixture mass) and mixed with a certain weight of conventional bentonite (CB) slurry. The rheology properties including the filtrate loss, viscosity, density, and pH testes of slurry with various bentonite dosages were measured to determine the reasonable CB dosage of slurry. The slump tests on PSB backfills with various mass slurries were conducted to determine the corresponding water content of backfills with slump 125 ± 5 mm. Under the applied pressure 100 kPa, the hydraulic conductivity to Pb(NO3)2 solutions (kc) of PSB backfills with various PAC contents was evaluated based on the modified filter press (MFP) tests, to ascertain the optimum PAC content of PSB backfills when permeated with Pb(NO3)2 solutions. Index properties, including the specific gravity (Gs) and liquid limit (wL) of PSB backfills, were measured after MFP tests. The MFP tests for PSB backfills were then conducted under various applied pressures to obtain the relationship between void ratio (e) and hydraulic conductivity of backfills. Finally, the flexible-wall permeability test (FWP test) under osmotic pressure 100 kPa was conducted to verify the effectiveness of the MFP test. The results indicate that slurry with 8% bentonite dosage is the reasonable choice in slurry wall construction. PSB has lower GS and higher wL compared to SB; increasing Pb concentration leads to GS of PSB increased and wL of PSB decreased. PSB with 0.6% PAC content is supposed as the optimum proportion of backfills when permeated with concentrated Pb(NO3)2 solution. PAC adsorbs large amount of bound water, which leads to higher water content (w) and e of PSB backfills, while lead ions (Pb) cause the diffuse double layer (DDL) of bentonite compressed and e of PSB backfills reduced. The kc of PSB-0.6 remains lower than 10−9 m/s and increases less than 10 times though the Pb concentration was up to 500 mM, demonstrating that the hydraulic performance of backfills can be improved effectively in Pb(NO3)2 solution by the additive PAC. The comparison results between k from MFP tests and FWP tests show that the MFP test is an effective and easy evaluation of hydraulic conductivity of backfills.

This study aims to investigate workability and microstructural characteristics of sodium hexametaphosphate (SHMP)-treated calcium bentonite (Ca-bentonite) as a potential material for soil–bentonite slurry trench cutoff walls. First, a series of Marsh viscosity, filtrate loss, density, and pH experiments are performed on bentonite – tap water slurries containing Ca-bentonite amended with 0%–8% SHMP dosages. Subsequently, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and zeta potential tests are conducted to explore microstructural characteristics that control the mechanisms of SHMP treatment. The results indicate that the workability of the slurry is significantly improved with SHMP addition. The SEM, XRD, and zeta potential analyses show that SHMP-amended Ca-bentonite possesses a more dispersed structure and higher negative zeta potential relative to the unamended Ca-bentonite. The mechanisms of SHMP amendment are identified to be exchange of bivalent calcium cations in Ca-bentonite by monovalent sodium cations in the SHMP, sorption of the SHMP anions that give the clay system a steric stabilization and increased negative surface charge density, and sequestration of the bivalent calcium cations on the Ca-bentonite. Overall, the SHMP treatment is effective in making the Ca-bentonite slurry amenable for use in the soil–bentonite slurry trench wall construction.

Pore pressure dissipation during piezocone testing provides a unique tool for estimating the hydraulic properties of in-situ backfills in soil-bentonite (SB) slurry trench cutoff walls. Six tests were performed in an SB slurry trench cutoff wall located in Jiangsu Province, China. The pore pressure dissipation curves obtained are non-monotonic, which, as far as the authors are aware, is reported for the first time in SB cutoff walls. The non-monotonic dissipation curves are attributed to the redistribution of excess pore pressures between the base soil clods and the rest of the backfill around the cone. Four existing interpretation methods are adopted to analyze the measured non-monotonic piezocone dissipation curves. The horizontal coefficients of consolidation (ch) of the backfills obtained by three methods are close to each other and in agreement with the results of fixed-ring consolidometer tests, while the other method gives a high overestimate. The hydraulic conductivities (kh) of the backfills are also estimated by four methods, three based on dissipation test results and one based on piezocone penetration data. kh estimated by consolidation theory are close to the results of flexible wall permeameter tests. Two empirical expressions for dissipation tests give relatively low kh, but the method based on penetration gives kh much larger than the laboratory test results.

Hexavalent chromium (Cr(VI)) in groundwater impose serious health problems for human society. This study investigates the potential of using calcium (Ca) bentonite amended with sodium hexametaphosphate (SHMP) as a backfill constituent material in the soil-bentonite slurry trench wall to envelop the Cr(VI) impacted groundwater. The hydraulic conductivity ( K ) and consolidation of backfill comprising of 80 wt% sand and 20 wt% SHMP-amended Ca-bentonite were determined via flexible-wall permeameter tests and oedometer tests , respectively. Microstructure characterizations of the amended bentonites before and after contamination were also explored. The results indicated that when the permeated liquid changed from tap water to Cr(VI) solution, the tested specimens exhibited a 1.0 to 1.2-fold variation in short-term K, with all K values fall in range of 2.1 × 10−10 to 2.5 × 10−10 m/s. This mild variation may be attributed to terminate the tests without achieving chemical equilibrium. On the other hand, the Cr(VI) solution had insignificant effect on consolidation of the amended backfill, which is attributed to the dominated incompressible sand matrix skeleton in the backfill that withstood the consolidation pressure and shield the negative effects of the contaminated solution. The microstructure images revealed that the Cr(VI) resulted in relatively strong interlink between particles. Overall, the SHMP-amended bentonite is promising for enhancing Cr(VI) containment performance of the soil-bentonite slurry trench wall backfills.

Landfills containing municipal solid waste (MSW) are increasing with growing population and consumption rate in Australia. However, construction of conventional containment systems such as slurry walls are a cost-effective and timesaving approach to control the leachate diffusion, they are weak barriers when exposed to volatile organic compounds (VOCs) or heavy metals, which are abundant in municipal solid wastes. This study investigates effect of sawdust addition on hydraulic conductivity and compressibility of the Soil-Bentonite (SB) slurry cut-off wall. A series of hydraulic conductivity and consolidation tests performed on SB backfill amended with 2%, 5% and 10% sawdust contents. The results showed that application of sawdust reduced the final hydraulic conductivity (kf) in the range of 2.13 × 10−10 ≤ kf ≤ 3.5 × 10−10 m/s. The computed hydraulic conductivity values using consolidation theory (ktheory) also showed an identical decreasing trend in the range of 5.10 × 10−11 ≤ ktheory ≤ 3.50 × 10−10 m/s under 24 ≤ σ′n ≤ 1280 kPa effective overburden pressure (σ′n). The coefficient of consolidation (cv) was computed using Casagrande and Taylor methods showed a good agreement range value. Additionally, the computed compression index (Ci) and swelling index (Cs) were calculated using void ratio and effective overburden pressure graphs (e - logσ′n) showed that application of sawdust had no significant impact on settlement of the SB backfill.

In the era of knowledge-based economy, innovation is ubiquitous and new technologies emerge in an endless stream. Many traditional construction techniques with inherent deficiency has been gradually replaced by new ones. On account of current construction of pile foundation engineering with slurry wall protection, slurry is manually replenished and slurry indexes are repeatedly measured by manual work, which affects the construction schedule and keeps security risks. This thesis proposes a new technique, in which slurry pressure variation values replace the specific gravity changes and linkage with slurry pump is utilized, which achieves automatic replenishing of slurry in pile foundation construction and realizes intelligent construction of pipe foundation engineering with slurry wall protection.

Cement bentonite mixtures are often used to build slurry walls for the containment of both aqueous and non aqueous pollutants, due to their quite low hydraulic conductivity and relatively high ductility and strength. Although their hydro-mechanical behaviour in saturated conditions has been studied in the past, a part of the slurry wall is expected to rest above the groundwater level. The hydraulic characterization in unsaturated conditions is then particularly relevant to evaluate the performance of the barrier, especially when it is aimed at containing non aqueous pollutant liquids which are lighter than water (LNAPL). These non wetting fluids rest above the water table and their penetration is possible just if the barrier is unsaturated. This paper presents some preliminary results of a laboratory characterization of the water retention behaviour of three different cement bentonite mixtures. The mixtures, prepared at cement – bentonite mass ratios ranging from 4:1 to 6:1, were immersed in water and cured for 28 days. Their water retention behaviour was then determined along drying and wetting paths through different techniques, namely axis translation, filter paper and vapour equilibrium. In the high suction range, the water content – suction relationship was found to be independent of cement-bentonite ratio. In the low suction range, the water content at a given suction was found to decrease for increasing cement bentonite ratios.

Cement bentonite slurry cutoff walls are used to encapsulate pollutants within contaminated areas, so avoiding their spreading in the environment. In both temperate and arid climates, at shallow depths, slurry walls are exposed to interaction with the atmosphere and thus to relative humidity values which might induce desaturation and significant shrinkage. This note presents the main results of a study aimed at investigating the impact of drying processes on the integrity and the hydraulic performance of cement bentonite slurry walls. Cement bentonite samples were cured under water for different times (1 months, 2 months and 4 months) and then dried naturally by exposing them to the laboratory environment (T = 21 °C, relative humidity approximately 38%). Once dried, the bottom of the samples was placed in contact with a thin layer of water to induce wetting. The distribution of the electrical conductivity within these samples was evaluated through Electrical Resistivity Tomography measurements, and electrical conductivity maps were converted then into maps of water contents on basis of a phenomenological relationship. The reconstructed water contents compared very well to the measured ones. Drying induced a limited cracking of the samples, which might affect to some extent the hydraulic performance of the barriers.

The rail link between Geneva Cornavin Station, Eaux-Vives Station and Annemasse (CEVA) is currently under construction including a cut-and-cover tunnel built by slurry walls located in the alluvium of the Foron River. The covered trench cuts the groundwater table flow which causes a rise of the water table on one side of the tunnel. Thirty wells were built in order to convey water from the aquifer on one side of the tunnel to the other. For each well, traditional pumping has been replaced by a self-priming multiphase siphon in order to lower energy costs. The operating principle of the system is based on the sustaining of a free-surface vortex flow in a vacuum chamber. In this way, the multiphase siphon is primed to allow water to be transferred from either side of the tunnel. A physical model of the conveyance system has been constructed at a scale of 1:1 in order to avoid scale effects from the presence of air water mixture and due to the free-surface vortices sensitivity to scaling, particularly in a vacuum atmosphere. In this study, the results from the physical model are used to validate a Smoothed Particle Hydrodynamics (SPH) numerical simulation of the complex flow conditions. The DualSPHysics code is employed and the results presented herein regarding the depth discharge relationship are encouraging for further application in vortex flows and such devices where conventional Eulerian modelling approaches can be challenging. As far as the authors are aware, this is the first application of SPH in simulating vortex chamber flows and the result bodes well for further application in this area.

Groundwater below many basins that have been used to store coal combustion residuals (CCRs) may have concentrations of certain inorganic constituents in excess of applicable regulatory standards. Given that many inorganic CCR constituents are also naturally occurring in the aquifer matrix, their detection may not always be indicative of a release from the CCR unit. Inorganics may be present at elevated levels in groundwater due to natural or background conditions, or due to changes to the aquifer geochemistry resulting from the presence of the CCR basin, which then mobilizes these naturally occurring constituents beneath the CCR unit. Care must be taken to identify the source(s) and the release mechanism(s) of potential CCRrelated impacts. If a link between a CCR unit and an inorganic groundwater exceedance has been established, stakeholders may be faced with the need to evaluate groundwater remedial alternatives to address these impacts. This paper conceptually discusses potentially applicable remedial approaches, including (i) monitored natural attenuation, (ii) hydraulic control using ex situ and in situ methods, (iii) permeable reactive barriers, (iv) slurry walls, and (v) oxidation-reduction–altering approaches. Additionally, this article explores potential water reuse options available at many power generating stations. © 2019 The University of Kentucky Center for Applied Energy Research and the American Coal Ash Association All rights reserved.

It has been found that four reinforced concrete flue stacks being constructed in late 80-ies and early in 90-ies of the 20 th century and being operated at various thermal power stations show practically no settlement, and this fact is not taken into account by any applicable regulatory documents. Foundations of these stacks were designed at the same time and they have been protected by patents of Russian Federation and Republic of Belarus. They represent circular bases made of reinforced concrete piles buried tightly together and forming so-called “slurry wall” with common monolithic reinforced concrete grillage. The grillage presents a direct extension of the stack shaft. One of these stacks has been built in Russia, and three – in Belarus. Due to significant differences in soil conditions and loads in each case, it is a fair assumption to say about regularity of the observed phenomenon. Notwithstanding the fact that circular foundations significantly decrease steel and concrete consumption, construction period and labour input, they have not yet received adequate attention from the side of scientific community and designers. While considering specific examples of the constructed stacks the paper reveals an opportunity to apply calculations which efficiently use passive soil resistance. The presented calculations and designs of the existing foundations make it possible to assess probability of the proposed methodology for the foundations which are analogous in design and which have closed in-plane structure not only for industrial buildings and structures.

The common procedures for stability analysis of slurry-supported trenches are typically two-dimensional (plane strain), despite the fact that observed failures in the field possess three-dimensional (3D) characteristics. A limit equilibrium (LE) solution for the stability of a slurry-supported trench is presented, where failures are constrained to a finite length. A rotational 3D failure mechanism, derived from variational LE analysis of the slope stability, is adopted and modified to account for the stability of a slurry-supported trench as well as very narrow trenches. The results are presented in the form of stability charts that yield a safety factor for narrow excavation of a given trench. Due to mathematical constraints on the resulting rigid 3D failure geometry, the critical surface of a deep and narrow trench emerges above the toe, termed the shallow failure. Once a shallow failure is initiated, it progressively propagates down to the toe. This above-toe failure mechanism may overestimate the safety of deep excavations in cohesive soils. Consequently, for shallow failures, an alternative approach is introduced to assess the safety of such progressive failures, which ultimately will emerge through the toe. The three-dimensional end effects are investigated to highlight their impact on the stability of a trench, indicating that end effects are most pronounced in purely cohesive soil, diminishing in cohesionless soil. End effects are significant for toe failures in slurry trenches, potentially impacting design.

The stability of slurry trench is of importance in diaphragm wall construction. The local stability of slurry trench under seepage application is investigated in this research. In the current research, the local instability of slurry trench is identified as the soil collapse in an instable sublayer and a three-dimensional translational failure mechanism is developed. In this mechanism, the local stability is initialed by the movement of a single rigid block and the seepage application is accounted by introducing the analytical model of semi-confined seepage. The stability is analyzed through kinematic approach and the upper bound solution of safety factor is deduced as a result. The stability is evaluated by optimizing the mechanism for the local failure. Using the current solution, the seepage effect on the stability is analyzed. Regardless of seepage, the stability is mainly dependent on the shear strength of the sublayer. Under seepage application, the failure zone is enlarged and the safety factor decreases as a result. The effect of seepage on the stability is significantly influenced by piezometric head difference Δ p and leakage ratio λ of the sublayer. The validity of the current solution is examined by investigating the case of diaphragm wall installation in Suzhou, China.

Västlänken i Göteborg är ett tunnelprojekt för järnväg som skall byggas under centrala Göteborg. Tunneln byggs genom både berg och lera, projektet kommer att använda sig av ett flertal tekniker och konstruktionslösningar. Västlänken är ett av de första stora infrastrukturprojekt i Sverige där slitsmurar används som permanenta konstruktioner. På uppdrag av Trafikverket har två olika typer av stödmurskonstruktioner undersökts med avseende på deras klimatpåverkan. Konstruktionslösningarna är en temporär spont med tillhörande tunnelvägg och en slitsmur. Slitsmuren används både som en temporär konstruktion under byggskedet och en del i den permanenta tunnelväggen. Slitsmurar har först nyligen blivit godkända att användas som delar av permanenta konstruktioner av Trafikverket. Av denna anledning finns det inte mycket information om konstruktionens klimatpåverkan. Syftet med rapporten är att undersöka klimatpåverkan från de två olika konstruktionslösningarna. Jämförelsen har gjorts med hjälp av livscykelanalyser för att få den mest övergripande analysen. En livscykelanalys (LCA) är ett verktyg för att synliggöra en produkts totala miljöpåverkan under dess livstid. Detta åstadkoms genom att alla de olika delprocesser som krävs för att skapa produkten inventeras och analyseras. LCA har utförts med datorprogrammet SimaPro och databasen Ecoinvent. I SimaPro har båda konstruktionslösningarna modellerats och deras miljöpåverkan sedan beräknats med ReCiPe 2016. Indata till LCA har samlats in från ritningar och diskussioner med experter på området. Resultatet från livscykelanalysen visar att slitsmurarna i detta projekt har större klimatpåverkan än konstruktionslösningen med spont och en platsgjuten betongmur. För slitsmuren står armering samt betong för den största delen av klimatpåverkan och för sponten är det den stora mängden stål som krävs vid de kraftiga dimensionerna. Då en del av konstruktionerna inom projektet ej var färdigprojekterad när denna rapport författades rekommenderas ytterligare studier på ämnet för att validera resultaten The West Link Project is as tunnel project for the railroad that will be constructed below central Gothenburg. The project is built through clay and solid rock thus making use of several techniques and structural solutions. The West Link Project (Västlänken) is the first major infrastructure project in Sweden where diaphragm walls are used as a part of the permanent structure. Two different structures have been examined on behalf of the Swedish Transport Administration, with regards to their climatic impact. The two structures examined are a temporary sheet pile with a cast-in-place concrete wall that is used as a part of the tunnel wall, and a diaphragm wall. The diaphragm wall is used as an earth retaining wall during the construction stage and as a part of the permanent tunnel wall. Diaphragm walls have just recently been approved as parts of permanent structures by the Swedish Transport Administration. Due to this there isn’t a lot of information available on their climatic impact. The purpose of this paper is to examine the climatic impact of these two different structures. The comparison has been performed by the use of a lifecycle analysis to get the most comprehensive analysis. A lifecycle analysis (LCA) is a tool that helps to get a perspective on a product’s total environmental impact over the course of its lifetime. This is accomplished by doing an inventory of all the different processes involved in its production. For the LCA the computer program SimaPro, and the database Ecoinvent were used. In SimaPro both of the structure have been modelled and their environmental impact has been calculated with ReCiPe 2016.Input for the LCA have been gathered from drawings and communication with experts. The result of the LCA shows that in this project the diaphragm walls have a higher climatic impact than the sheet pile and concrete wall. With regards to the diaphragm wall the majority of its climatic impact is from the large amounts of reinforcement and concrete used. For the sheet pile the steel used to manufacture sheets of the dimensions used in the project is the largest contributing factor. Due to the fact that some of the structures in the project are still being at the design stage at the time of writing further studies are recommended to validate the results.

The present study investigated the effectiveness of two soil-bentonite slurry wall backfills, specifically sand/conventional Na-bentonite (NaB) and sand/hexametaphosphate (SHMP)-amended Ca-...

Low-permeability slurry trench cutoff walls are commonly constructed as barriers for containment of subsurface point-source pollution or as part of seepage-control systems on contaminated sites. A method to estimate wall thickness in slurry wall design is proposed based on decoupling the advective and dispersive components of contaminant fluxes through the wall. The relative error of the result obtained by the proposed method compared with that by an analytical solution was found to increase as the ratio of the specified breakthrough exit concentration (c*) to the source concentration (c0) increased. For c*/c0 of less than 0.1, which covers common practical situations, the relative error was not greater than 4% and was always conservative, indicating that the proposed method provides sufficient accuracy for design. For a given breakthrough criterion (i.e., c*/c0), the relative error was low for the scenarios having either a low or high column Peclet number, where either dispersion or advection dominates the contaminant migration, respectively, and the relative error was high for the scenario having an intermediate column Peclet number, in which case the coupling effect of advective and dispersive migrations is relatively high.

Hydraulic conductivity of soil-bentonite (SB) slurry-trench cutoff walls is highly influenced by the stress state. A model based on force equilibrium is proposed to predict the stresses in ...

“Check and monitoring of condition of concrete slurry wall, jet-grouting and frozen soil fences by crosshole sounding method in underground construction” includes investigation results on the state of massifs of artificial soils established using a set of geophysical acoustic methods. Object of investigation are slurry wall panels’ body and joints, jet-grouting and frozen soil underground fences. Methods of geophysical investigation are crosshole acoustic and ultrasonic sounding from holes or embedded tubes. For investigation use crosshole sounding apparatus APZ-1 developed by LLC “Geodiagnostika” and ultrasonic device Pulsar 2.2 DBS. The author postulates that non-destructive testing provides the most accurate information about the state of the enclosing structure in the place of manufacture in the underground space.

Soil–bentonite slurry-trench cutoff walls using backfill consisting of on-site sandy soil and Na-bentonite are extensively used as engineering barriers for the purpose of achieving relatively low hydraulic conductivity. The amendments such as zeolite to backfill are considered to improve the contaminant sorptive capacity. At some sites, local clayey soil, Ca-bentonite and natural zeolite may be available for an alternate backfill. However, studies on the workability (in terms of slump), compressibility and hydraulic conductivity of such zeolite-amended clayey soil/Ca-bentonite backfills for the cutoff walls are very limited. This paper presents a comprehensive laboratory investigation on the workability, compressibility, and hydraulic conductivity of fine-grained zeolite-amended clayey soil/Ca-bentonite backfills using several series of slump and oedometer tests. Kaolin is used as the model clayey soil, and it is amended with various amounts of Ca-bentonite (7.8–8.4%) and zeolite (10–40%) to prepare zeolite-amended kaolin–bentonite backfills. The test results are compared with previous studies on zeolite-amended sandy soil/Na-bentonite backfills as well as compacted zeolite–bentonite liners to assess the effects of zeolite content and zeolite grain-size on the compressibility and hydraulic conductivity. The results indicate that the water content required to achieve a target slump (100–150 mm) for the backfills increases with increasing zeolite content. Liquid limit can be a useful index for a preliminary estimation of the water content required to achieve the target slump for the backfills presented in this study and zeolite-amended sandy soil/Na-bentonite backfills reported in previous studies. The results reveal that the hydraulic conductivity of the zeolite-amended clayey soil/Ca-bentonite backfills with void ratio ranging from 0.54 to 1.45 is generally lower than the typical regulatory limit (10− 9 m/s). The addition of fine-grained zeolite has insignificant influence on the compressibility and hydraulic conductivity of both clayey soil/Ca-bentonite and sandy soil/Na-bentonite backfills. A proposed empirical method based on the framework of Kozeny–Carman equation can predict the hydraulic conductivity of zeolite-amended clayey soil/Ca-bentonite backfills values within the range of 1/3 to 3 times those calculated from the oedometer tests. The proposed method is also shown to estimate the hydraulic conductivity of the compacted zeolite–bentonite liners from previous studies with reasonable accuracy. Additional research is recommended to evaluate the proposed zeolite-amended backfill using tap water and also by direct measurement of hydraulic conductivity using falling-head or constant-head testing method.

A remediação de contaminações em águas subterrâneas e no solo tem sido alvo de estudos devido ao alto impacto e custo de recuperação. Um dos métodos utilizados para a contenção de plumas contaminantes é a cortina vertical. O presente trabalho tem por objetivo escolher a partir de dados de propriedades índice, hidráulicas, físico-químicas e mecânicas, o melhor material, entre quatro alternativas, a ser utilizado nas cortinas verticais com a função de contenção de plumas contaminantes. Os quatro tipos de materiais analisados foram um solo natural (SN), um solo natural com bentonita (SB), um solo natural com bentonita e cimento (SBC) e bentonita pura (B). O Método de Análise Hierárquica (AHP) foi utilizado como ferramenta de tomada de decisão para escolha da melhor solução de contenção, sendo utilizados dois critérios (caracterização e permeabilidade) e três subcritérios para a caracterização (caracterização geotécnica, físico química e resistência). Devido à indisponibilidade de dados de resistência da bentonita foram realizadas três análises, as quais indicaram o solo natural (SN) como sendo a melhor alternativa devido à influência relativa da permeabilidade.

A series of centrifuge model tests exploring the effects of different types of slurry on long-trench stability in soft clay were conducted. The influence of groundwater conditions relative to trench stability was examined by constructing long trenches using different slurries. The soil deformation and surface settlement induced by the excavation of the trench are found to be closely related to slurry type and excavation depth of the long trench. Increasing the bentonite concentration of the slurry has beneficial effects on stability: 1) larger particles can improve local and global stability in cases where filter cakes do not form, and 2) larger viscosity can promote filter cake formation on the walls of long trenches excavated in soft clay and enhance their stability.

Modern urban policies, particularly in major towns, involve the active use of underground space that poses the problem of assessing the impact of excavation on the existing buildings as one of the most urgent. Surface and semi-closed construction methods are currently widespread in the process of urban civil and transport underground facilities construction. The depth of excavation can reach 30 m, but more often, in everyday practice common foundation pits have shallower depth, accommodating 2-4 underground levels (6-12 m). In the process of solving such problems not only the forces occurring in the foundation pit fence are of great interest, but also a quantitative change in the stress-strain state of the rock mass. In modern engineering practice in order to solve them numerical methods based on the finite element method are widely applied, which can quantify soil stress-strain state. In this study, the authors present the investigation of the influence of various factors within their variation on the additional deformations of adjacent buildings located in the influence zone, using the design of experiment method. The study is based on 3-dimensional numerical simulation with the use of finite element method. Such calculated factors were taken: the depth of excavation (X ), modulus of deformation (X ), the distance to the building (X ) and distributed load of the building (X ). As a result, regression equations to determine the maximum additional deformationof building and horizontal displacement of the pit fence were derived from the calculations carried out. Also, the graphs describing these dependencies and illustrating the effect of each factor were presented.

In this study, we applieorithmd the inverse analysis alg to the prediction of displacement shape in the example construction and verified the feasibility of suggested algorithm. For this purpose, as information processing knowledge in the field of IT is required and the need for convergence with the major is emerged, it is intended to try to apply the algorithm to the construction sector. Prediction of displacement shape is very important since it is related to the earth pressure of slurry wall and effecting on the safety of slurry wall after anchor removal. 3 levels of inverse analysis were applied to the slurry walls in 3 sites and compared the measured displacement shape with predicted displacement shape of the last excavation construction. As the predicted displacement shape was matched well with the measured one, the applied analysis algorithm in this study can be applied to the excavation construction.

The bi-layer diaphragm wall is a new type of slurry wall, designed to improve watertightness and to counter leakage problems. These walls consist of two bonded concrete layers: the first, a conventional Reinforced Concrete (RC) diaphragm wall and the second, a sprayed Steel Fibre Reinforced Concrete (SFRC) layer with a waterproof additive. Here, we analyse and quantify the influence of different construction process parameters on the effectiveness of the bi-layer diaphragm wall technique. Thirty numeric simulations were conducted with an uncoupled structure-section analysis, placing special emphasis on the SFRC layer contribution. The results show that, in all cases, the main flexural strength is provided by the RC layer, with a secondary flexural contribution (between 8% and 15%) by the sprayed SFRC layer. Using satisfactory spraying sequences (detailed herein), a reduction in the steel reinforcement of the RC layer can be obtained in every structural configuration and construction sequence, reaching a maximum percentage reduction of 7.0% of the total bending reinforcement. The displacements are almost completely governed by the thickness of the first layer, and a minor reduction (less than 7.3%) is obtained, when the second layer is included.

Thispaperpresentstheresultsofalaboratorystudyonthesubaqueousdepositionofsandparticlesfromsediment-ladencircularjets on horizontal and inclined beds. Four sets of experiments were carried out to investigate the effects of jet characteristics, bed slope, sediment size, and sediment concentration on the growth and development of the sediment mound. Three distinct flow regimes can be identified as de- veloping regime, spreading regime, and backup regime. It was found that in the developing regime, deposition height and width formed by the continuous release of sediment particles grow faster than the mound length. Slurry jet flow in the spreading regime was diverted from the axial direction to the sides and caused more deposition on both sides of the mound. Backup regime started when the deposition height and width reachedtheirmaximumvalues.Inthiscondition,aslurryjetpushedsedimentbacktothenozzleandeventuallyblockedthe flow.Theinitiation of sediment deposition was estimated, and predictions were compared with experimental results. Variations of the deposition length scales, moundbasearea,andangleofdepositionwithtimeweremeasured.Empiricalformulationswereintroducedtopredictdepositiondevelopment

The development of industry has brought serious heavy metal pollution in the soil. There are various kinds of site contamination remediation technologies. The slurry wall barriers technology has many advantages, such as low permeability, good chemical compatibility, and low cost, so it was widely used in groundwater and soil pollution control projects. In this paper, the application status of vertical barrier technology in contaminated sites is reviewed. Currently, those research progress at home and abroad payed more attention on barrier materials, barrier mechanisms, and site types.

Standard containment technologies for remediation of subsurface contaminants include slurry walls, reactive barriers, sheet piling, and grouting. Another less common technique is freezing contaminants in situ. Artificial freezing techniques can be used to create a frozen barrier that restricts migration of aqueous phase contaminants and, therefore, can provide subsurface containment at a variety of facilities, including underground tanks, nuclear waste sites, groundwater plumes, and in situ waste treatment areas. Frozen barriers are formed by using a series of subsurface freezing pipes. The adjacent soil forms a frozen column the length of the freezing pipe; and the diameter of the frozen soil column increases with time at a rate depending upon the specific soil properties, moisture content, and thermal conditions at a given site and refrigeration rate (i.e., pipe temperature). The barrier is completed once the increasing diameters of the frozen soil columns merge together, which is referred to as “freezing to closure”. A study was performed in Fairbanks, Alaska, to investigate how quickly a barrier can be created during the summer using actively cooled hybrid thermosyphons. Freezing to closure occurred after 42 days, the barrier was 1 m thick after approximately 49 days, and temperatures were below − 3 °C at the core of the barrier (in between the thermosyphons) after 60 days. The active system was turned off in the fall, and passive cooling of the ground continued through the winter. By the beginning of the following March, the frozen barrier was 3.8 m thick.

Slurry trenches are often used to impede groundwater flow or to contain soil and groundwater contamination. The stability of the slurry trench during excavation and prior to backfilling is a major concern in design. A horizontal slice method for stability analysis of slurry trenches, which allows consideration of soil stratification, is presented. Vertical force equilibrium for each slice of the sliding mass and horizontal force equilibrium for the whole sliding mass are considered on the basis of limit equilibrium. The factor of safety is obtained via the Newton–Raphson method and the critical slip surface corresponding to the minimum factor of safety is located by the pattern search method. The proposed method is verified via consideration of a previously reported problem. It is then applied to a full-scale field experiment in three-layer soils. The obtained minimum factor of safety and location of the slip surface of the sliding mass are in excellent agreement with the experimental measurements. Analyses of trenches having a weak layer at various depths demonstrate potential variations in slip surface inclination between soil layers.

The slug test is a viable method in estimating the hydraulic conductivity of the slurry trench wall backfill because of its ability to consider a more representative volume of the backfill and to reflect the in situ performance of the construction. A three-dimensional numerical model is developed to simulate the slug test in a slurry trench wall with the presence of bentonite cake on the interface boundary between the wall and the surrounding soil formation. Influential factors such as wall width (i.e., proximity of wall boundary), well deviation, vertical position of the well intake section, and compressibility of the wall backfill are taken into account in the model. The experimentally obtained hydraulic properties of the bentonite cake are also incorporated in a series of slug test simulations. The simulation results are then examined to evaluate the bentonite cake effect in analyzing practical slug test results in the slurry trench wall. The simulation results show that the modified line-fitting method can be used without any reduction factor for the slug test in the slurry trench wall with the presence of bentonite cake. A case study is reanalyzed with the assumption of existing bentonite cake. The results are compared with the previously reported results by the approaches used for the case of no bentonite cake (constant-head boundary) and upper-bound solution (no-flux boundary). The modified line-fitting method and the type curve method produce similar results for slurry walls with bentonite cakes. The case study results demonstrate the importance of the bentonite cake effect in estimating the hydraulic conductivity of the slurry wall backfill.