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.
Basal reinforcement of embankments and supporting with piles is one of the most recent solutions for rapid embankment construction on soft foundation soils. This paper uses the Particle Image Velocimetry (PIV) to evaluate the performance of unreinforced and reinforced embankments over soft foundation soils in terms of maximum settlement at the embankment base, lateral displacements of the embankment toe and the strains in the reinforcement layer using the digital images captured during the centrifuge model tests at 40g. The reinforcement consisted of a single layer of a scaled-down model basal geogrid and additional support from end-bearing or floating piles. The paper examines the effect of varying embankment heights on the geogrid strains and deformation characteristics of subsoil under rapid embankment construction over unreinforced and reinforced soft foundation soil with varying support conditions. The unsupported reinforced embankments showed a peak geogrid axial strain near the toe, whereas it peaked near the mid- of the embankment for pile supported reinforced embankments. The study also investigates the failure mechanisms of unreinforced and reinforced embankments, with and without pile support, using shear strain contours derived from PIV analysis. The paper underscores the efficacy of PIV as a tool for visualising the deformation behaviour and failure mechanisms in soil during centrifuge model studies. Additionally, the research provides insights into the operation of an in-flight sand hopper used for embankment construction in centrifuge model studies. Post-investigation studies contribute to understanding the potential failure mechanisms in embankments supported by end-bearing and floating piles. Overall, this paper showcases the practical application of PIV in studying the challenges related to rapid embankment construction on soft foundation soils.
Stability issues and the resulting economic and human losses associated with soil-rock mixture slopes (SRMS) are significant concerns. To address these stability problems in SRMS, h-type anti-slide piles (hTP) have been recognized as reliable stabilizing structures. This research involves a series of five centrifuge model tests conducted to investigate the stress response of hTPs under various pile parameter scenarios. The experiments were designed to evaluate the impact of variables such as pile spacing, anchoring depth, and beam rigidity, leading to practical recommendations for the effective use of hTPs. Centrifuge tests unveiled that the rear pile undergoes an M-shaped bending moment distribution, marked by three crucial inflection points situated approximately at 1/4 h(2),4/7 h(2), and 5/6 h(2). In contrast, the front pile exhibits a V-shaped bending moment distribution, reaching its peak at a depth of 6/7 h(1). The alteration of the bending moment throughout the loading phases is divided into three distinct periods: the slow creep stage, the slow growth stage, and the rapid growth stage. Moreover, it was noted that the bending moment of hTP intensifies with an increase in pile spacing, while the depth of anchoring shows no significant influence on the magnitude of the bending moment.