The anisotropy of shear resistance depending on friction direction can be selectively utilized in geotechnical structures. For instance, deep foundations and soil nailing, which are subject to axial loads, benefit from increased load transfer due to greater shear resistance. In contrast, minimal shear resistance is desirable in applications such as pile driving and soil sampling. Previous studies explored the shear resistance by interface between soil and surface asperities of a plate inspired by the geometry of snake scales. In this study, the interface friction anisotropy based on the load direction of cones with surface asperities is evaluated. First, a laboratory model chamber and a small-scale cone system are developed to quantitatively assess shear resistance under two load directions (penetration -> pull-out). A preliminary test is conducted to analyze the boundary effects for the size of the model chamber and the distance between cones by confirming similar penetration resistance values at four cone penetration points. The interface shear behavior between the cone surface and the surrounding sand is quantitatively analyzed using cones with various asperity geometries under constant vertical stress. The results show that penetration resistance and pull-out resistance are increased with a higher height, shorter length of asperity and shearing direction with a decreasing height of surface asperity.

The expansion of a thick-walled hollow cylinder in soil is of non -self -similar nature that the stress/ deformation paths are not the same for different soil material points. As a result, this problem cannot be solved by the common self -similar -based similarity techniques. This paper proposes a novel, exact solution for rigorous drained expansion analysis of a hollow cylinder of critical state soils. Considering stress -dependent elastic moduli of soils, new analytical stress and displacement solutions for the nonself -similar problem are developed taking the small strain assumption in the elastic zone. In the plastic zone, the cavity expansion response is formulated into a set of first -order partial differential equations (PDEs) with the combination use of Eulerian and Lagrangian descriptions, and a novel solution algorithm is developed to ef ficiently solve this complex boundary value problem. The solution is presented in a general form and thus can be useful for a wide range of soils. With the new solution, the non -self -similar nature induced by the finite outer boundary is clearly demonstrated and highlighted, which is found to be greatly different to the behaviour of cavity expansion in in finite soil mass. The present solution may serve as a benchmark for verifying the performance of advanced numerical techniques with critical state soil models and be used to capture the finite boundary effect for pressuremeter tests in small -sized calibration chambers. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting 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/).

Seepage cut-off walls are common seepage mitigation measures in dikes to minimize seawater ingress. These cut-off walls are usually made of cement-bentonite (CB). The quality of this CB wall is critically important. Non-destructive testing would ensure quality control/assessment without damaging the wall's integrity. One such non-destructive technique is the measurement of electrical resistivity. Correlations can be established between electrical resistivity, strength, and permeability of CB mixes. Continuous monitoring of electrical resistivity across the CB wall would enable early detection of its properties instead of waiting for coring of samples after 14, 28, or 91 days of curing, which would introduce discontinuities in the wall. For in situ electrical resistivity measurement, electrodes of finite size are buried in an infinite soil medium, where As, the area of soil mass is much larger than Ae, the area of electrode. This is very different from laboratory measurement, of which As = Ae. Thus, the effect of boundary on these two situations is very different, and the correlation between resistivity and unconfined compressive strength, as well as between resistivity and permeability, established in a laboratory setup may not be suitable for use in in situ measurement condition. Hence, this paper aims to systematically study the impact of boundary on the electrical resistivity of CB mix. Consistent CB mix placed in boxes of different heights and widths (thus different values of As) was designed to study the boundary effect, with area of electrodes (Ae) kept constant. It was found that the electrical resistivity value increases with reducing As/Ae value, and As/Ae has to be greater than 25 to negate the effects of boundary on electrical resistivity. In addition, there is an issue on the direction of resistivity measurement. The in situ resistivity measurements were more conveniently carried out horizontally in an infinite soil medium, while the laboratory cored samples were normally measured in vertical direction. Thus, there is a need to study the anisotropy effect on electrical resistivity value of CB mix.