Land subsidence and pore structure of soils caused by the high-rise building group through centrifuge model test

Abstract

In the urban area of Shanghai, the dewatering of groundwater was controlled strictly and the engineering–environment effect of the high-rise building group became to be the main cause of land subsidence in Shanghai. Based on the high-rise building group in the soft soil area in Shanghai, the mechanism of land subsidence was studied in this paper by the centrifuge model test. The central area of the building group has larger subsidence and the subsidence superimposition effect is obvious. It can exceed the allowance and cause land subsidence hazard. The land subsidence affected by the different building distances was also studied. For smaller building distances, the subsidence superimposition effect is more obvious. The engineering characteristics of soils are controlled by the state of pore structure of soils to a great extent. The parameter of specific subsidence was put forward as a tie to analyze the relationship between land subsidence and pore structure of soils. The pore structure of each soil layer was studied by the mercury intrusion porosimetry test (MIP) and the pore distribution of each soil layer was studied by the fractal theory. There are mainly macropores in silty clay of layer no. 4, clayey soil of layer no. 8, silty sand of layer no. 7 and layer no. 9 in Shanghai. The ink-bottle effect exists in the intrusion stage in the MIP test. There are four different fractal dimensions in silty clay of layer no. 4 and clayey soil of layer no. 8 and three different fractal dimensions in silty sand of layer no. 7 and layer no. 9.