Loose sandy soil layers are prone to liquefaction under strong earthquakes, causing damage to civil engineering structures inside or upon the liquefied ground. According to the present Japanese design guideline on liquefaction countermeasures for river levees, the entire depth of the liquefiable subsoil below river embankments should be improved. However, this approach is not economical against deep liquefiable subsoil. To rationalize the design approach, this contribution investigated the performance of a floating-type cement treatment method, in which only the shallower part of the liquefiable subsoil is reinforced. A series of centrifuge shaking table model tests was conducted under a 50g environment. The depth of improvement (cement treatment) was varied systematically, and the effect of the sloping ground was examined. The experimental results revealed that the settlements of river embankments can be reduced linearly by increasing the depth of improvement. Moreover, the acceleration of embankments can be reduced drastically by the vibration-isolation effect between the cement-treated soil and the liquefiable soil. These effects contribute to the safe retention of the embankment shape even when the liquefied sloping ground causes lateral flows. Towards practical implementation, discussions on the effect of permeability on cement-treated soil were expanded. Furthermore, the stress acting on cement-treated soil during shaking was measured using an acrylic block to explain the occurrence of cracks in the soil. (c) 2025 Japanese Geotechnical Society. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Earthquake-induced soil liquefaction causes ground and foundation failures, and it challenges the scientific community to explore the liquefaction problem in deep deposit under strong shaking. Due to the capacity limitation of physical modelling facility, it is difficult to reproduce soil liquefaction response of deep sand ground by centrifuge shaking table test. To address this problem, a suite of centrifuge model tests were conducted with the aid of Iai's Type III generalized scaling law (i.e., GSL) to observe the liquefaction response of deep sand ground, where Models 1 and 2 were used to validate the GSL and Model 3 with the validated GSL stands for the deep sand ground with prototype depth of 80 m. The test results of Models 1 and 2 indicate that GSL generally performs well for small-strain shear modulus, nonlinear dynamic response of acceleration and the generation of excess pore water pressure, but leaves considerable errors for post-shaking dissipation process and ground settlement with large plastic strain. The test results of Model 3 indicate that liquefaction is also possible in depth of 30-40 m under shaking event of PBA = 0.4 g and Mw = 7.5. For deeper depth without triggering of liquefaction, a depthdependent power function relationship between the peak excess pore water pressure and Arias intensity has been established. The test results also revealed that consolidation and earthquake shaking history contribute to the development of soil anisotropy in a deep ground, leading to a continuous increase of anisotropy degree, which could be evaluated using the small-strain shear moduli in different stress planes under orthogonal stress conditions.

Stone columns are a resultful measure to increase the bearing capacity of soft or liquefiable foundations. The centrifuge model test and finite element method were employed to investigate the bearing capacity and deformation behavior of the stone column-reinforced foundation. Study shows that the modulus of the reinforced foundation exhibits significant anisotropy. A bulging deformation area is identified in the reinforced foundation where obvious horizontal deformation of the stone column occurs. The ratio of the column stress and soil stress is observed to change violently in this area. A homogenization technique is consequently deduced by employing the column-soil stress ratio as a key variable. The definition of the column-soil stress ratio is extended to reasonably describe the column-soil interaction under different stress levels and its approximation method is given. Based on the Duncan- Chang E-nu model, a simplified method using the homogenization technique is proposed for the stone column reinforced foundation. The proposed homogenization technique and simplified method have been validated by the centrifuge model tests and finite element analyses. This method properly addresses the nonlinear spatial characteristic of deformation and the anisotropy of the stone column reinforced foundation.

The presence of underground structures within fault zones has the potential to alter deformation patterns on the ground surface, thereby placing existing structures-typically regarded as safe-at risk. This paper presents findings from four centrifuge model tests and 3D numerical simulations exploring the effects of tunneling in fault zones. This study investigated the values associated with foundation rotation, surface deformations, and the patterns of fault rupture propagation through various soil strata. The results demonstrate that the presence of a tunnel alters the interaction pattern between fault rupture and foundation systems, which can lead to an increase in foundation rotation. Notably, the findings indicate that a precise consideration of superstructure shape can enhance foundation rotation by up to 23%. Furthermore, the presence of a tunnel in the fault zone causes substructures to endure major damage from vertical fault displacements exceeding 0.6 m. In contrast, these substructures experienced similar levels of damage at vertical fault displacements of 1.7 m in the absence of tunnels.

Precast driven piles are extensively used for infrastructure on soft soils, but the buildup of excess pore water pressure associated with pile driving is a challenging issue. The process of soil consolidation could take several months. Measures are sought to shorten the drainage path in the ground, and permeable pipe pile is a concept that involves drainage channels at the peak pore pressure locations around the pile circumference. Centrifuge tests were conducted to understand the responses of permeable pipe pile treated ground, experiencing the whole pile driving, soil consolidating, and axially loading process. Results show that the dissipation rate of pore pressures can be improved, especially at a greater depth or at a shorter distance from the pile, since the local hydraulic gradient was higher. Less significant buildup of pore pressures can be anticipated with the use of permeable pipe pile. For this, the bearing capacity of composite foundation with permeable pipe pile can be increased by over 36.9%, compared to the case with normal pipe pile at a specific time period. All these demonstrate the ability of permeable pipe pile in accelerating the consolidation process, mobilizing the bearing capacity of treated ground at an early stage, and minimizing the set-up effect. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

A critical investigation of three constitutive models for clay by means of analyses of a sophisticated laboratory testing program and of centrifuge tests on monopiles in clay subjected to (cyclic) lateral loading is presented. Constitutive models of varying complexity, namely the basic Modified Cam Clay model, the hypoplastic model with Intergranular Strain (known as Clay hypoplasticity model) and the more recently proposed anisotropic visco-ISA model, are considered. From the simulations of the centrifuge tests with monotonic loading it is concluded that all three constitutive models give satisfactory results if a proper calibration of constitutive model parameters and proper initialisation of state variables is ensured. In the case of cyclic loading, the AVISA model is found to perform superior to the hypoplastic model with Intergranular Strain.

Physical modeling is an efficient method to simulate practical geotechnical problems and to provide insights into soil behavior. This study used geotechnical centrifuge models equipped with motorized pulling systems to pull coupons (thin metal plates) at constant speeds horizontally through clean, saturated sand models that were liquefied by cyclic loading. The model setup was aimed to mimic shearing mechanisms, large shear strains, and large strain rates observed in field-scale flow slides. In-flight cone penetration testing and bender element-based shear wave velocity measurements helped in characterizing soil state at coupon levels before liquefaction. In addition, a miniature pressure transducer was embedded in the coupon along its top horizontal surface to directly measure pore pressure response on the shear surface within the liquefied soil. In total, 11 coupon pulls were completed, with 6 of the 11 tests providing shear-induced pore pressure measurements at the coupon surface. Measured coupon pulling forces and pore pressure responses at shear-surface and free-field were interpreted to identify key behaviors. These key behaviors illustrated that relatively low coupon velocities were required to maintain liquefied conditions at the coupon surface. In addition, pulling force recovery during pore pressure dissipation appeared to be related to coupon velocity (i.e. strain rate).

The objective of the present study is to evaluate the performance of a levee when subjected to flooding and subsequent seepage through centrifuge model tests. For this, six centrifuge model tests were conducted on a 240 mm high levee model at 30g in a 4.5 m radius large beam geotechnical centrifuge available at the Indian Institute of Technology Bombay, India. A custom-developed flooding simulator is employed to induce identical flood rates on the upstream side of the levee models. Further, using (a) geocomposite (GC) and (b) sand-sandwiched geocomposite (SSGC) as internal chimney drain, the suitability of GC material for dissipation of pore-water pressure (PWP) is also studied. The results of the centrifuge tests are presented and discussed in terms of the development of upstream flood function, subsequent PWP development within the levee body, and the surface settlements observed at the levee's crest. Further, the influence of an internal chimney drain, the material used for its construction, and its type and composition on the seepage response of the levee is discussed in detail. The performance GC chimney drain placed within the levee subjected to flooding-induced seepage is compared with a conventional sand chimney drain. It is observed that a GC-based chimney drain with sand cushioning on both sides in the horizontal portion of the chimney drain performs well. Further, digital image analysis of SEM micrographs of exhumed GC after centrifuge tests and the analyzed PWP data during sustained flooding-induced seepage is found to corroborate well.

This study presents a series of centrifuge model tests that were conducted to investigate the grouting mechanism and its effect during rectangular pipe jacking in soft soil. A new jacking grouting device was developed to simulate the entire grouting process in the centrifuge model tests. The influence of grouting on the friction at the lining-soil interface and vertical displacement of the tunnel lining was analysed. In addition, the impact of the grouting slurry's viscosity and fluid loss on ground surface settlement and the friction at the pipe-soil interface was also examined. The results indicate that grouting plays a significant role in mitigating the friction and vertical displacement of the tunnel lining caused by excavation. Furthermore, the study shows that reducing the viscosity of the grouting slurry can reduce the friction coefficient at the pipe-soil interface, thus facilitating the advancement of pipe jacking. The use of a low fluid loss grouting slurry is also recommended to improve control over ground surface settlement. These findings are crucial for enhancing the efficiency and safety of rectangular pipe jacking in soft soil.

The deformation characteristics of river embankments on soft ground, improved by circular deep mixed columns and a combination of circular and grid-form columns, were investigated via two centrifugal model tests. The results indicate that the slope stability of the river embankment was effectively sustained in both cases. The combined reinforcement method exhibited superior overall performance, significantly reducing settlement. The greatest settlement was observed at the top of the river embankment, and although the settlement had not fully stabilized one year after construction, the settlement rate had slowed. Compared with the circular reinforcement alone, the river embankment maximum settlement was reduced by 25.3% in the combined reinforcement. Additionally, the grid-form columns effectively reduced the horizontal displacements in the middle and lower parts of the foundation. The deep-mixed columns performed effectively in providing support and reinforcement, and none of the piles reached the bending capacity during the test process. Given the stiffness difference between the columns and the surrounding soil, the stress distribution exhibited a stress concentration effect in the model. The measured column soil stress ratio ranged between 2 and 3, which is considered reasonable. The pronounced stress concentration effect of the mixing columns contributed to a faster consolidation rate of the foundation. On the basis of the measured settlement and excess pore water pressure, the degree of consolidation of the circular column-reinforced foundation one year after construction reached over 90% and 80%, respectively. For the foundations reinforced with combined circular and grid-form deep mixed columns, the degree of consolidation reached over 80% and 75%, respectively.