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This study proposes a new model in explicit form to predict the diameter of the jet grouting column of three popular jet grouting systems (i.e., single, double, and triple). The proposed model can quantify the uncertainty associated with the prediction. Bayesian model selection was used to determine the optimal models and, the bootstrap sampling method was adopted to avoid bias in the collected database. The predictions agree well with the measured data, and the 95% credible intervals can cover almost all the measured data on the testing dataset, which indicates the robustness of the proposed model. A simple formula combined with a table was established to facilitate the engineers in applying the proposed model. The results reveal that soil type has a significant impact on diameter prediction. Uncertainty quantification can reveal possible fluctuations in column diameter and is vital to get a cost‐efficient design. [ABSTRACT FROM AUTHOR]

The settlement performance of an immersed tunnel in the Hong Kong–Zhuhai–Macau Bridge (HZMB) transportation project is described. The geological profile underlying the immersed tunnel is presented and the corresponding field monitoring system is introduced. The function of semi-rigid elements is analysed. The observed results related to longitudinal deformation patterns during construction (e.g. long-term settlement, differential settlement and structural behaviour) are described and analysed. Differential settlement occurred when there was a large variation in soil properties, at the joints of two adjacent elements and in different segments of the same element. Differential settlement occurred in both the longitudinal and transverse direction. During the operational period, permanent settlement was strongly related to back-silting. Tide loading and the immersion of adjacent elements may have caused transient settlement related to elastic deformation, but tide loading had less influence on the permanent settlement. [ABSTRACT FROM AUTHOR]

In the Hong Kong–Zhuhai–Macau Bridge mega project, several ground treatment methods were applied in the transition area between the artificial island and immersed tube tunnels to reduce the potential uneven foundation settlement underlying the tunnel, as the backfilled sand layer is more than 10 m around it. One of the foundation improvement methods involves the combination of preload and high-pressure jet grouting (HPJG) columns. Current field tests, such as core bowling, standard penetration test, and plate loading test, are not suitable for evaluating the strength of this reinforced foundation. This study presents a full-scale load test to examine the construction quality and effects of an HPJG-reinforced foundation. A novel method was designed based on the Boussinesq equation to simulate the additional stress distribution from the immersed tube tunnel. The tangent modulus method considering the impact of modulus nonlinearity was employed to calculate the nonlinear settlement of the treated foundation. Preferable settlement results were obtained using a set of pre-embedded high-precision hydrostatic leveling systems. Both the measured data and calculated settlement demonstrate the reasonableness of the present in situ test. [ABSTRACT FROM AUTHOR]

Columnar inclusion is a versatile and cost-effective technique for improving weak soils. Currently, most approaches are based on the "equal strain" assumption to calculate the deformation of soft ground reinforced by columnar inclusions. In this study, a new model to simulate the behavior of column-reinforced soft soil under equal stress conditions based on the variational principles is proposed. The proposed model satisfies the force equilibrium and deformation compatibility simultaneously, which is seldom fulfilled in traditional empirical methods or other analytical models. The corresponding analytical solution is obtained and its accuracy is verified by comparing it with the numerical solutions using finite element analysis. The comparisons of the proposed solution with an existing solution show that the proposed solution can provide very close agreement over a wide range of parameters while the existing solution is only able to provide a reasonable agreement for a certain range of stiffness ratio of the column and soft ground. In addition, a parametric study is made to illustrate the influence of various parameters on ground settlement predictions. The parametric study indicated that, by increasing the ratio of elastic modulus between the stone column and surrounding soils and the ratio between the radius of the stone column and the space of the stone column, the load transfer effect has been significantly improved, and the ground settlement becomes smaller. Furthermore, the Poisson's ratio of the surrounding soil also has a very significant effect on ground settlement, while the effect of the Poisson's ratio of the stone column on ground settlement is less significant compared with that of the surrounding soil. [ABSTRACT FROM AUTHOR]

This short communication reports a water inrush hazard during the construction of the Shijingshan Tunnel in Zhuhai, Guangdong, China. On 15 July 2021, a water inrush accident occurred at the construction site 1.16 km away from the tunnel entrance, resulting in 14 casualties. The purpose of this study is to investigate and discuss the water inrush process in this atypical case. The principal causes of this tunneling accident include the special geological conditions at the construction site, high hydraulic conductivity at the part that connects the underground water system and the overlying water body (the Jida Reservoir), and the impact of heavy rainfall. Moreover, four significant suggestions are proposed to prevent the possible occurrence of water inrush disaster: (1) assessing the risk level in areas prone to water inrush; (2) getting a comprehensive geological prediction based on borehole data and artificial intelligent methods; (3) establishing a monitoring system during the tunneling process; (4) strengthening the self-protection skills of construction workers. [ABSTRACT FROM AUTHOR]

This paper presents the roof fall collapse of a coal mine that occurred, causing 20 deaths and 1 injury, in Qinghai Province, China, on 14 August 2021. After the primary investigation of this incident and a brief description of the rescue action undertaken, this report discussed the possible reasons behind this disaster. The fissure water and damaged rock mass are the dominant triggering factors of this incident. Little concern for risk assessment and monitoring systems is one of the main man-made mistakes. Consequently, the reflections and suggestions are put forward to reduce or prevent the occurrence of roof fall incidents in coal mines. The noteworthy actions that are necessary in coal mine projects are conducting risk assessments based on geological condition and building proper support systems for coal mines considering he situation in situ. [ABSTRACT FROM AUTHOR]

The vesicular structure of volcanic rocks may disrupt the fluid flow in fractures and make the mechanism of fracture flow more complicated. This study evaluated the characteristics of fracture flow associated with vesicular structure. To quantify the vesicular structure in the fracture surface, different arrangements and sizes of drilled holes were designed and manufactured in artificial single fracture samples and three associated factors of area ratio, depth, and diameter of drilled holes. A series of laboratory tests was conducted with different vesicular structure and fracture aperture. A nondimensional parameter, λ, was introduced to reveal the vesicular structure and the relationship between λ and the Reynolds number was established. The test results illustrate that the Reynolds number is sensitive to the vesicular structure in fracture surface. The vesicular structure could enhance the fracture flow rate when the flow rate is relatively small and vice versa. However, the fracture flow has no obvious change when varying each influencing factor related to vesicular structure separately. A new formula was obtained to estimate the fracture flow rate considering vesicular structure and the input variables contains fracture aperture and hydraulic gradient. The proposed formula was proven to be reasonable by comparing the measured data from the single fracture tests of real volcanic basalt samples. [ABSTRACT FROM AUTHOR]

Abstract Soil arching effect results from the non-uniform stiffness in a geosynthetic-reinforced and column-supported embankment system. However, most theoretical models ignore the impact of modulus difference on the calculation of load transfer. In this study, a generalized mathematical model is presented to investigate the soil arching effect, with consideration given to the modulus ratio between columns and the surrounding soil. For simplification, a cylindrical unit cell is drawn to study the deformation compatibility among embankment fills, geosynthetics, columns, and subsoils. A deformed shape function is introduced to describe the relationship between the column and the adjacent soil. The measured data gained from a full-scale test are applied to demonstrate the application of this model. In the parametric study, certain influencing factors, such as column spacing, column length, embankment height, modulus ratio, and tensile strength of geosynthetic reinforcement, are analyzed to investigate the performance of the embankment system. This demonstrates that the inclusion of a geosynthetic reinforcement or enlargement of the modulus ratio can increase the load transfer efficiency. When enhancing the embankment height or applying an additional loading, the height of the load transfer platform tends to be reduced. However, a relatively long column has little impact on the load transfer platform. [ABSTRACT FROM AUTHOR]

In this study, analytical solutions are presented for the axisymmetrical consolidation of an unsaturated soil stratum on the basis of Fredlund and Hasan's one-dimensional consolidation theory. Two different loading conditions, i.e., instantaneous loading and ramp loading, were considered. The derivation process of the proposed analytical solution is simpler in contrast to the existing analytical solutions and it was verified to be accurate using an analytical solution in the literature. In addition to the analytical solutions under the assumption of free strain, the analytical solutions under the assumption of equal strain were further derived. In the parametric study, the variations in the excess pore-water and pore-air pressures as well as the average degree of consolidation are presented. Graphs are given to show the influence of the different hydraulic conductivity ratios between the air and water phases as well as the construction time (under a ramp loading condition) to the consolidation process. These two factors have significant impact on the consolidation of the air phase but little influence on the consolidation process of the water phase. [ABSTRACT FROM AUTHOR]

SUMMARY This paper presents a simple analytical solution to Fredlund and Hasan's one-dimensional (1-D) consolidation theory for unsaturated soils. The coefficients of permeability and volume change for unsaturated soils are assumed to remain constant throughout the consolidation process. The mathematical expression of the present solution is much simpler compared with the previous available solutions in the literature. Two new variables are introduced to transform the two coupled governing equations of pore-water and pore-air pressures into an equivalent set of partial differential equations, which are easily solved with standard mathematical formulas. It is shown that the present analytical solution can be degenerated into that of Terzaghi consolidation for fully saturated condition. The analytical solutions to 1-D consolidation of an unsaturated soil subjected to instantaneous loading, ramp loading, and exponential loading, for different drainage conditions and initial pore pressure conditions, are summarized in tables for ease of use by practical engineers. In the case studies, the analytical results show good agreement with the available analytical solution in the literature. The consolidation behaviors of unsaturated soils are investigated. The average degree of consolidation at different loading patterns and drainage conditions is presented. The pore-water pressure isochrones for two different drainage conditions and three initial pore pressure distributions are presented and discussed. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

To prepare the pyrotechnical battery with high energy density, reliability and practicality, the processing technology of pyrotechnical battery was researched. The main factors which affect preparation of pyrotechnical battery were analyzed and the contrast of them was made. The optimum technical conditions were determined by orthogonal experiments. The experimental results indicate that proper process parameters of Zr/CuO pyrotechnical battery are as follow. For anode sheet, the ratio of radius to thickness is 5 : 1 and the charge density is 4.0 g/cm³ ; for cathode sheet, the ratio of radius to thickness is 10 : 1 and the charge density is 3.3 g/cm³, and, for diaphragm sheet, the ratio of radius to thickness is 25 : 1 and the charge density is 2.1 g/cm³. [ABSTRACT FROM AUTHOR]

Surcharge combined with vacuum preloading is a common technique for accelerating the consolidation process in ground improvement. A unit cell model for the axisymmetric consolidation of a soft soil using a prefabricated vertical drain (PVD) under a surcharge, combined with vacuum preloading, is investigated in this study. Based on this model, analytical solutions for a multi-layer soil system are put forward and the explicit expressions for two-layer and one-layer systems are presented. The accuracy of the proposed solution is verified using an analytical solution available in the literature. In the parametric study, the influencing factors on the consolidation process, such as, the smear zone, the PVD spacing, the hydraulic conductivity in the radial direction, the coefficient of vacuum decrease, are taken into account. The water flow in the radial direction plays an important role in the consolidation process while the impact of the vertical flow mainly develops around the interfaces between two adjacent layers. In addition, the proposed analytical solution is applied in a case history with three different layers and the results are reasonable. [ABSTRACT FROM AUTHOR]