The generation of excess pore water pressure (EPWP) and liquefaction characteristic of soils under seismic loading have long been topics of interest and ongoing discussion. Based on the structural state exhibited in the liquefaction process, the mechanical property of saturated coral sand is divided into solid, pseudo-fluid, and liquid phases. New indices, zeta q (generalized deviator strain evolution) and zeta(y)q (generalized deviator strain evolution rate), are proposed to evaluate the evolution and evolution rate of complex deformation. In the solid phase, the saturated coral sand primarily exhibits the properties of a continuous solid medium, the peak EPWP ratio (rup) shows a power correlation with generalized deviator strain evolution amplitude (zeta qa). While in the pseudo-fluid phase, the saturated coral sand primarily exhibits mechanical behavior characteristic similar to that of a fluid, and the rup shows a significant arctangent function relationship with generalized deviator strain evolution rate amplitude (zeta(y)qa). The correlation of rup with zeta qa and zeta' qaduring liquefaction is significantly affected by loading conditions (cyclic stress ratio, CSR, loading direction angle, alpha sigma, and loading frequency, f). To quantify the impact of these loading conditions on the generation of rup in different phases, unified indicators delta S (for the solid phase) and delta L (for the pseudo-fluid phase) are defined. Eventually, An EPWP model based on mechanical property exhibited in different phases is developed, which has normalized the effects of loading conditions. It provides a comprehensive framework to predict the rup of saturated coral sand under complex geological activities, and this model facilitates the understanding and simulation of the mechanical properties and behavior of saturated coral sand during the liquefaction process.

The soil fabric varies significantly depending on the deposition process that forms the grain skeleton. Each deposition method produces a specific type of soil fabric, which can be linked to a particular soil density. When represented as relative density, determined using limit densities from standard index tests, a wide range of relative densities can be observed for different sands produced by the same deposition method. The influence of this variation in relative density, resulting from a single deposition method, on the development of the excess pore water pressure (PWP) should be further investigated. A fast testing of the excess PWP accumulation in sandy soils during undrained cyclic shearing can be easily performed using the newly developed PWP Tester. In the PWP Tester, specimens are prepared through sedimentation in water, which yields a comparable fabric in different sands but significantly different relative densities. Despite these relative density differences, the rate of the excess PWP evolution during undrained shearing is remarkably similar among different sands. This indicates that relative density should not be regarded as a primary factor influencing the development of the excess PWP and that the soil fabric plays equal or even a greater role.

This study investigates the pore water pressure (PWP) behavior of soil around large-diameter open-ended thin- walled piles (LOTPs) during impact driving using a large deformation finite-element method. A comparative analysis of the PWP accumulation curves of the soil inside, outside, and below the LOTP tips with different diameters and wall thicknesses during impact driving is conducted under the same hammering solution. The PWP development is dependent on the absolute distance from the pile surface to the location of the soil and the dimensions of the LOTP. The excess pore water pressure (EPWP) accumulates and gradually dissipates, and its level decreases with increasing pile diameter. However, a negative excess pore water pressure (Ne-EPWP) is identified during hammering. Based on the above findings and analyses, a PWP prediction equation for LOTP during driving is proposed, and the predicted curves are compared with the numerical results. The influence of PWP accumulation after penetration of 2d (d is the LOTP internal diameter) does not increase significantly. This equation can provide the initial distribution field of PWP in saturated clay for LOTPs, thereby facilitating pile drivability analyses.

For slope instability caused by rainfall, there are some differences between ideal rainfall conditions and actual rainfall conditions. In order to study the stability of slopes under heavy rainfall, this paper therefore takes the 7.20 special rainstorm in Zhengzhou as an example. Four factors, namely average annual rainfall q, soil permeability coefficient anisotropy kr, water table height h(w), and suction friction angle phi(b), were selected as variables. The finite element method was used to analyze the variation rule of initial pore water pressure (IPWP) at the top and bottom of the slope under various factors during the rainfall process, the limit equilibrium method was used to calculate the safety factor (F-s) after the rainfall, and the grey correlation analysis method was used to analyze the sensitivity of factors affecting slope stability under heavy rainfall. The result shows that the pore water pressure at the top of the slope varies more than that at the bottom of the slope during rainfall. The lower the initial pore water pressure, the lower the safety factor of the slope at the end of rainfall. The sensitivity of each factor to the slope safety factor is in the following order: phi(b)>k(r)>h(w)>IPWP.

The occurrence of earthquake-induced soil liquefaction poses a significant threat, leading to extensive damage to building foundations and other structures, resulting in substantial economic repercussions. The seismic performance of geotechnical systems is markedly influenced by the saturation level of the soil. This study examines the impact of dynamic response on Palar sand. Cyclic triaxial tests were conducted on partially saturated finegrained loose sand with a relative density of 35 % and a degree of saturation ranging from 65 % to 75 %. These tests were carried out at a strain rate of 0.1 % and confining pressures of 50 and 75 kPa. The study findings reveal that an increase in back pressure corresponds to a rise in the excess pore water pressure ratio of the sand. Additionally, the sand undergoes liquefaction as the number of cycles increases, and the degree of saturation decreases for different confining pressures at frequencies of 0.75 and 1 Hz. It was observed that soil liquefies more rapidly at lower strain rates with an increase in effective confining pressure. Conversely, at higher frequencies, soil liquefaction occurs in a smaller number of cycles. Comparing the effects of confining pressure and frequency, a damping ratio of 13 % and a shear modulus of 40 MPa were achieved at a frequency of 0.75 Hz and a confining pressure of 50 kPa. The shear modulus of partially saturated sand decreases with an increase in the initial degree of saturation due to specific characteristics of the Palar sand and the loading conditions.

This study investigates the impact of nearby structures on the cyclic settlement mechanisms of shallow foundations in liquefiable soils using a numerical model based on Biot's porous media theory. The model predicts excess pore water pressure and settlement by coupling equilibrium and continuity equations, solved using an implicit time integration scheme. Soil nonlinearity under cyclic loading is represented using generalized plasticity, boundary surfaces, and non-associated models. Three scenarios are simulated to study the effect of spacing between light and heavy foundations and variation in acceleration intensity. Results show that as spacing between foundations increases, lateral displacement and settlement decrease. Excess pore water pressure generation also decreases with increased foundation spacing. Soil just below the foundation exhibits maximum settlement, decreasing with depth. When input acceleration increases from 0.1 g to 0.15 g and 0.2 g, settlement increases by 40%-55% and 90%-110% respectively for both light and heavy foundations, regardless of spacing. Excess pore water pressure also increases sharply with higher acceleration intensity. The findings highlight the importance of considering foundation-soil-foundation interaction effects in liquefaction-prone urban settings and provide insights for designing resilient shallow foundations. The advanced numerical modeling approach offers engineers a more informed way to mitigate liquefaction risk and build safer, more durable structures in earthquake-prone areas.

An earthquake is a natural occurrence that has the potential to trigger liquefaction. In fine sandy soil layers with a shallow water table, earthquakes can cause a rapid increase in excess pore water pressure (PWP), compromising the soil's effective strength and increasing the risk of liquefaction. According to the Indonesian Liquefaction Vulnerability Zone, North Sumatra is categorized as a liquefaction area. Langkat is one of the regencies in North Sumatra that is categorized as having a moderate liquefaction vulnerability. Therefore, Langkat was chosen as a research area to investigate liquefaction potential using pore water pressure (PWP) with empirical methods by Yegian and Vitelli (1981) and numerically using Deepsoil V7.0. The study area consists mostly of sand with shallow groundwater levels due to its proximity to rivers and high seismic zones associated with the Sumatran fault. The analysis is based on Standard Penetration Test data and laboratory tests from 2 boreholes with a depth of 30 m. The lts show that full liquefaction potential exists at BH 01, a depth of 9-11 m below the ground surface with r(u) > 0.8 and a limit of gamma(max) >= gamma. Marginal liquefaction occurs at BH 02 at a depth of 3.5 m with r(u) > 0.8 and gamma(max) < gamma(limit). Evaluation of the excess pore water pressure ratio in area prone to liquefaction is important because this condition can cause rapid damage. The low bearing capacity of the building foundation is proven by the r(u) value approaching 0.8.