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| Laboratory-scale model test on settlement incurred by foundation pit dewatering considering the barrier effect of pre-existing metro station |
| ZENG Chaofeng1，2，CAI Gang1，2，ZHU Long1，2，ZHANG Zuhao1，2，CHEN Hongbo1，2，XUE Xiuli2，LONG Sichun3，LUO Guijun4 |
(1. Hunan Provincial Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring，Hunan University of Science and Technology，Xiangtan，Hunan 411201，China；2. School of Civil Engineering，Hunan University of Science
and Technology，Xiangtan，Hunan 411201，China；3. School of Earth Science and Space Information Engineering，
Hunan University of Science and Technology，Xiangtan，Hunan 411201，China；4. China Construction
Fifth Engineering Division Co.，Ltd.，Changsha，Hunan 410011，China)
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Abstract In urban environment，the existing underground structures could exert a barrier effect on groundwater seepage and soil movement. According to current research results，this barrier effect would either aggravate or diminish the ground settlement，while the specific characteristics of ground deformation is associated with the types and spatial distribution of the underground structures. In this paper，laboratory-scale model tests were conducted to investigate the mechanism of dewatering-induced deformations when a foundation pit is adjacent to a pre-existing metro station. With installing deformation and stress sensors in the physical model of pit-strata-station，the variations of groundwater level outside the pit，ground surface settlements，wall deflections and lateral pressure on both sides of the enclosure wall were monitored in real time during dewatering. All the monitored results were compared with those from another model test without a subway station outside the pit under the same pumping conditions；based on the comparison，the impact mechanism of the barrier effect incurred by metro station on the dewatering-induced foundation pit deformation is revealed. Results show that as to the case with metro station outside the pit，the same dewatering operation as the case without metro station would induce smaller water yield of the pit，smaller enclosure wall deflection but greater ground surface settlement and greater groundwater drawdown on both sides of the enclosure wall. In foundation pit design，engineers could consider reducing the number of pumping wells to achieve the same pumping effect，and should evaluate the barrier effect of adjacent underground structures on foundation pit deformation to provide a more reasonable supporting scheme.
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2023, Vol. 42 
