Submarine landslides are a geological hazard that may cause significant damage, and are among the most serious problems in offshore geotechnics. Understanding the mechanism of submarine landslide/offshore structure interaction is essential for risk assessment, but it is challenging due to its complexities. In this study, ten centrifuge tests were conducted to determine how offshore wind turbines founded on four piles respond to consecutive submarine landslides. The tests highlighted two mechanisms of soil deformation and foundation settlement associated with the landslide cycle: (1) deformations of the clay were associated with induced excess pore water pressure, and increased with the number of landslides; and (2) by contrast, foundation settlements largely depended on the dynamic impact of the first cycle and remained unchanged for the remaining events. The settlements were 0.5 m for the 10 m pile foundation and about 0.1 m for the 20 m pile foundation, both in clay and in sand. It was also found that increasing pile length reduces the excess pore water pressure, soil deformation and foundation settlement.

Shallow foundations are commonly used to support various equipment in industrial projects. If the subsoil is too weak to withstand the equipment loads, the settlement or tilting of the foundations takes place. To avoid further distress to such foundations, weak soil beneath the damaged foundation is required to be strengthened. This paper presents a similar case study wherein the strengthening of subsoil was performed beneath the shallow foundations which experienced settlement and tilting beyond the permissible limits due to the presence of weak subsoil. The stabilisation of soil was performed using injection grouting with colloidal silica-based chemical grout to prevent further settlement and tilting of foundations. The particulars of the chemical stabilisation program, injection methodology, chemical consumption, field trials, and laboratory test results are explicated in this paper with the details of post rectification performance of the test foundation. The properly executed injection grouting using chemical components was observed to be an effective measure to stabilise the subsoil by enhancing its engineering properties to a certain extent. The key factors that can affect the performance of colloidal silica-based chemical and precautions to be considered during soil stabilisation are also discussed in this paper.

This study aims to develop hazard curves to assess the reliability of shallow foundation design on sandy soils. The random finite element method was employed to analyze the elastoplastic behavior of soils with spatially varying deformation modulus and angle of shearing resistance, which were generated as random fields and assigned to the analysis models. The output distributions were fitted with a corresponding probability density function (PDF), and the probability of exceedance (Pf) for determined damage limits was estimated from these PDFs, forming the proposed hazard curves for the determined anisotropy ratios. The method proposed in the study was validated by a database containing field test measurements, and a sample problem was presented to exemplify the application of hazard curves. The significant contribution of this study is to form the hazard curves for superficial foundations on sandy soils by considering both the elastoplastic behavior of soil and the influence of all effecting parameters, which satisfy the serviceability limits in the foundation design codes. The curves proposed in this study provide an approach for probabilistic investigation of superficial foundations taking the variability of sands into account and robust technique for the reliability-based design of strip footings with a serviceability limit state.

Liquefaction-induced settlement of shallow foundations is the result of bearing capacity failure in undrained conditions and sedimentary settlement during the post-liquefaction process. The bearing capacity of a shallow foundation is highly dependent on the size and dimensions of its footprint. In addition, the reduction in shear strength in liquefiable soil, a key parameter for estimating bearing capacity, depends on the excess pore water pressure generated during an earthquake. This study aims to investigate the impact of earthquake motion on the extent of liquefaction-induced settlement in shallow foundations. A parametric study was conducted by varying the input earthquake motions in a three-dimensional response history analysis to directly consider the interaction between the soil and superstructures. The numerical analysis model constructed for the parametric study was rigorously calibrated using a reference dynamic centrifuge test in a prototype scale. The effects of the horizontal boundary and drainage conditions in the numerical model were closely examined during calibration. The parametric study results indicate that the intensity measures of an earthquake, which quantify the energy associated with the number of reversals, exhibit a close correlation with the resulting liquefaction-induced settlement as opposed to other conventional earthquake motion parameters, such as peak acceleration, magnitude, and frequency.

Rotary penetration test is a newly developed in-situ testing technology in recent years, which combines the advantages of large drilling depth and continuous, intuitive, good repeatability, fast testing speed, and economy of cone penetration testing data. It uses static pressure and rotational torque to penetrate the soil stratum at a constant speed by standard conical double helix probe, recording the penetration resistance of the probe during the process of uniform penetration, the resistance torque, and water pressure during the process of soil damage. It is a new in-situ testing method for testing and studying the physical and mechanical properties of soil stratum. Through the analysis of mechanism and a large number of field tests, the results of the rotary penetration test (RPT) were analyzed by comparing with data of cone penetration test (CPT), drilling test, field pile test, and others; the characteristic indexes of rotary penetration as well as a series of analysis method and empirical formula were proposed, i.e. how the rotary penetration test results were applied to classify the strata, judge the soil category, determine the basic bearing capacity of the ground and the ultimate bearing capacity of the concrete bored pile. The research results were of great significance to enrich the in situ test method and promote the application and popularization of the rotary penetration technology.

Foundation settlement is a common problem in civil engineering. In the case of un-even settlement, it can lead to structural deformation and damage, which seriously affects the safety and reliability of the project. Therefore, the influence of adjusting the stiffness of the foundation on un-even settlement was analyzed through finite element analysis to effectively solve un-even settlement. By simulating the settlement of soil under different foundation stiffness and load conditions, the influence of foundation stiffness adjustment on soil deformation and settlement distribution was analyzed, and its impact on structural safety was evaluated. These studies confirmed that thickened layers could effectively solve the un-even settlement. Within the range of 0.2 to 1.0 meters, the difference in thickness was the greatest. The adjustment of differential settlement by layer thickness was phased and decreased with increasing thickness. Adjusting the stiffness of the foundation could effectively solve un-even settlement, reduce differences in soil settlement, and improve the overall stability and safety of the structure. These results have important guiding significance for the design of foundation and the solution of un-even settlement problems in engineering practice and provide certain reference and basis for further research.