Centrifugal Model Tests On Bearing Properties Of Support In Excavation With Deep Tunnel Engineering

With continuous progress of the urban modernization process,the high-rise building industry has sprung up rapidly,bringing more and more various deep foundation pit projects into our eye shot.The testing data on deep foundation pit at work site is very limited,which brings difficulties to the study of mechanical properties of support structure in excavation.Developing deep underground space is the main trend of urban planning in the future.It’s very significant to carry out a systematic and detailed theoretical research on deep foundation pit engineering.Based on pumping station pit and silo pit in a tunnel system prototype engineering,we carry out centrifugal model tests combined with numerical simulation method to analyze test results,demonstrate the rationality of prototype supporting design and discuss the regulation,which includes deformation of underground continuous wall,distribution of soil pressure and land subsidence.The main conclusions are as follows:1.The soil pressure at the back of the pumping station foundation pit is basically linear with depth and distribution curve shows nonlinear characteristics at circular support text points.Circular arch effect makes earth pressure redistribution in buried depth of support area,which is proved that the ring brace plays a certain inhibitory effect on deformation of the underground continuous wall.2.The circular underground continuous wall deformation of pumping station foundation pit shows a trend that it increases firstly and decreases afterwards with depth.The peak deformation is 23 mm and does not change anymore.The peak deformation of T shaped wall which occurs at the top of foundation pit is 8.8mm and that satisfies the deformation control requirements in the specification.3.The support of circular foundation pit has an advantage over rectangular foundation pit in the respect of wall underground continuous wall deformation.The connection between support and wall is unstable with increasing of rectangular foundation pit underground continuous wall deformation.Arch effect of circular foundation pit plays a certain role in convergence of the wall deformation.4.The surface settlement of shaft foundation pit obeys parabolic regular distribution and the maximum settlement is about 15 meters away from the underground continuous wall,accounting for about 29 percent of the excavation depth.The initial stage is the excavation of the soil layer and the change of surface settlement is relatively rapid.There is little change in surface settlement when the foundation pit excavates to the rock layer in the later period,and it gradually tends to a stable level.