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Although the Horncastle project was a new build embankment, the cut-off, in the form of a slurry wall, was installed once the embankment construction was complete. As such the installation process was in practice the same as a slurry wall being installed as a part of a dam repair and/or rehabilitation works, and therefore the experience is directly transferable. Such works can be an alternative to a steel sheetpile cut-off design and therefore a key component of the sustainable management of dams. This paper is based on the author's experience on site, working full time for the main contractor supervising the installation of a sub-contractor design to a performance specification. This paper will take the reader through all stages of the installation process, from set-up and logistics, to daily operations; what the process is actually like on the ground and the health and safety and environmental considerations. For each of these stages, the paper discusses the challenges faced and their resolution, with the aim of providing engineers with an insight into the key issues to consider when planning, designing or supervising a slurry wall installation operation.

The soil-bentonite slurry wall (SBSW) is an established ground improvement technology that continues to find applications. It's often the best and most economical vertical barrier to essentially st...

Soil–bentonite (SB) and slag–cement–bentonite (slag-CB) slurry trench cut-off walls are widely used low-permeability subsurface barriers against groundwater or contaminants. The bentonite in SB wal...

One of the most telling artifacts in the 9/11 Memorial Museum is the slurry wall, a vestige in situ of the pre-9/11 World Trade Center complex, preserved under Section 106 of the National Historic ...

This paper presents an analytical three-dimensional rotational mechanism for the limit analysis on the overall stability of slurry trenches in layered cohesive soils. The proposed mechanis...

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.

Ethiopia is currently developing irrigation schemes like micro dams to improve its food security. Chalchal Dam project is one of such dams to be constructed in the Bale Zone of Southeastern Ethiopia. However, this dam is subjected to engineering geological problems due to the presence of carbonate and shale rocks in this area. To address this problem, engineering geological mapping, discontinuity surveying, core drilling, geophysical surveying, in situ permeability, and laboratory testing were carried out. From these integrated investigations, the dam site is underlain by colluvial and alluvial soil deposits, sandstone, limestone with decomposed shale, shale, marly limestone, and massive limestone rocks with different degrees of weathering and fracturing. The Lugeon test conducted along the dam axis revealed the presence of potential seepage zones at the left abutment and river center in which the former is underlain by highly permeable rocks with Lugeon values as high as 39.58 and the latter with permeable rocks with a Lugeon value of 9. The geo-mechanical properties of rocks such as friction angle, cohesion, and modulus of deformation at the dam site, as determined using Hoek–Brown failure criteria, were in ranges of 21.52 to 32.06°, 0.123 to 3.006 MPa, and 0.747 to 9.308 GPa, respectively. The bearing capacity of the dam foundation was determined using empirical methods and the result pointed out that the allowable bearing capacity of the dam foundation ranges from 0.116 to 5.321 MPa. After the removal of colluvial and alluvial deposits along the dam axis, ground improvements were recommended along the dam axis mainly in terms of curtain grout and slurry trench or concrete cutoff.

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.

A waste plaster landfill site, established as a high-density polyethylene (HDPE) sheet pile surrounded by a slurry wall to isolate possible contaminants within the landfill, was investigated using ...

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.

To construct urban metro stations, the concrete diaphragm walls are widely used as the support of deep foundation. During the installation of concrete diaphragm wall, the global instability of slur...

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.

The exposure of rebar in diaphragm wall was discovered after excavation in more than 20 subway stations, along the lines 1 to 4 in Suzhou, China. Such phenomena were investigated from strata formation, hydrogeological condition, construction techniques, adjacent surcharge load and other aspects. Based on field investigation, in situ testing and numerical simulation, the disturbance of trenching operations and the main factors that affect the stability of the diaphragm wall during the trenching process are analyzed comprehensively. The results show that the deformation behavior and stability of slurry trench walls are mainly influenced by strata characteristics, adjacent surcharge loading, formation of bentonite filter cake on trench walls, pressure of a confined aquifer, height of slurry filling and slurry density. The underground water pressure in the confined aquifer of silty soil layers is considered as one of the main controlling factors, which is verified by the subsequently dewatering and trenching tests. During the construction process, the deformation and stability of the trench walls can be improved by adjusting and controlling the crucial controlling factors. Further, relevant remedial measures as well as the preventive methods during the process of constructing diaphragm walls and subsequent soil excavation are addressed.

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.

This chapter provides an overview of the commonly used groundwater exclusion techniques, including the factors affecting the application of each technique. A wide range of exclusion techniques are available to form cut-off walls or barriers around civil engineering excavations. The method is mainly used when groundwater-induced instability is a major concern – either because ground conditions are favourable or because pre-drainage methods of groundwater control have been deployed to lower groundwater levels. A vibrated beam wall has little structural value, and the principal groundwater control applications have been to form deep temporary cut-off walls through easily penetrated ground conditions such as sands. Cross section through a slurry trench wall. The wall toes into a low permeability stratum to form a groundwater cut-off. The top of the wall is replaced by a cap of compacted clay to prevent drying and cracking of the hardened slurry.

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 paper proposes a new computational method for the analysis of slurry infiltration in saturated sand considering the relationship among soil deformation, slurry seepage and particle dispersion. The nonlinear governing equations for slurry infiltration are derived, and the corresponding variational principles based on time increment are established. The finite element method is employed to solve the problem. The computational results are validated with the reported test data, which shows that this method is much better than the traditional Herzig method in predicting the particle deposition. The proposed method is demonstrated through an example of slurry infiltration in slurry trench.

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.

Bentonite-water slurry trenches are utilised not only in underground excavations, but also in geo-environmental protections. Slurry trench can be used to prevent leaks and spills of the contaminant...