Search

The vertical–horizontal curtain system (VH curtain) is sometimes utilized in foundation pit dewatering under complex hydrogeological conditions. However, the working mechanism of this system when the horizontal curtain is semi-permeable and cannot completely cut off the bottom aquifer remains unknown. A transparent soil physical model test was performed to reveal the water control mechanism of the VH curtain system with a semi-permeable horizontal curtain. A multi-point inert tracer with a high-speed camera was used to photograph the seepage process. The seepage mode was revealed via a model test. With the Shanghai deep tunnel project as background, a numerical simulation was performed to understand the utilization of the VH curtain. The influence of horizontal curtain position, horizontal curtain thickness, horizontal curtain hydraulic conductivity, and VH curtain combination form on the seepage path around the foundation pit and on the drawdown of water level inside and outside the pit were studied. Results provide a basis for the engineering application of the VH curtain pumping well system. [ABSTRACT FROM AUTHOR]

Groundwater level has to be lowered during deep excavation. A vertical curtain is usually adopted to control the drawdown inside and outside a foundation pit in a built-up area. However, the cost and working difficulty increases substantially with the rise in depth of vertical curtains. In the manuscript, a man-made horizontal seepage reducing body (HSRB) was introduced to shorten the vertical curtain depth and control drawdown. With the No. 4 shaft foundation pit of Guangyuan Project, Shanghai as background, HSRB was proposed in foundation pit dewatering. Microbially induced carbonate precipitation grouting technology was recommended to form an environment-friendly HSRB. Numerical method was used to simulate and understand the influence of position, thickness, and hydraulic conductivity of HSRB on groundwater level. The non-separated HSRB was better than the separate HSRB. Decreasing HSRB hydraulic conductivity was better than increasing HSRB depth. Four seepage modes were summarized considering vertical curtain penetration conditions into multi-aquifer, and the fifth seepage mode was formed for vertical curtain using man-made HSRB, which can be referred by similar engineering applications. [ABSTRACT FROM AUTHOR]