Panpan Shen’s research while affiliated with Shanghai Investigation, Design & Research Institute (SIDRI) and other places

According to current research, the small-strain soil hardening model (HSS model) is being used more and more widely because it can consider the small-strain characteristics of soil, making the corresponding numerical analysis results more accurate. At present, research into the test value of HSS model parameters of soil mass is mainly concentrated in Shanghai. Given the limits of the test conditions, there has been notably insufficient research into the value of small-strain parameters. Considering the regional differences of soil parameters, this paper, based on an actual project, conducts the HSS model parameter test value study on the main soil layers in the west of Hangzhou, focusing on the value study of small-strain parameters. The corresponding results are used for numerical analysis. The research shows that, compared with the Mohr–Coulomb model, the numerical analysis results using the HSS model are obviously closer to the measured data, and the prediction of the lateral deformation and its change law of the diaphragm wall is obviously more accurate. At the same time, when other HSS model parameters are unchanged, the numerical results using in situ small-strain parameters are closer to the measured results than using indoor small-strain parameters, and the corresponding deformation prediction accuracy is higher. The research results provide valuable references for determining HSS model parameters and engineering applications in the western area of Hangzhou.

Geotextile filters have gained extensive applications in geotechnical and geoenvironmental drainage systems. Despite of the abundant research about geotextiles filtering coarse-grained soils, there is little experimental study on the performance of geotextiles filtering fine-grained soils. Since clogging and blinding of geotextiles are more likely to occur in clayey soils, a complex filtration performance of the filters is expected, posing great challenges to the long-term durability of the filtration system. In this research, long-term permeability tests were conducted on silty clay filtrated by three types of nonwoven needle-punched geotextiles. Comprehensive results regarding the permeability evolution, soil retention and clogging behavior were obtained. Interior clogging behavior of the geotextile was checked after the tests by means of scanning electron microscopy. Significant reduction around two orders of magnitude from 10⁻⁸ m/s to 10⁻¹⁰ m/s was observed in the permeability coefficient of the silty clay-geotextile system after 90 days of seepage flow. The influence of filtration opening size of the geotextile was obviously noticed in the initial permeation process, while the thickness played an increasingly important role at the later stage. Geotextile with the larger thickness and smaller filtration opening size had more soil retention and poorer filtration performance. In addition, a theoretical equation relating permeability coefficient and filtration opening size of nonwoven geotextile under clogged condition was proposed.