Model Test Research About Influencing On Land Subsidence During To Loess Pit Drainage

Aiming at solving the problem of land subsidence caused by well-pumping in pit at the loess area of Xi’an, after aecessing to lots of documents,systematieally summing up domestic and iniernational research status of engineering precipitation caused land subsidence and a detailed study about loess and pit percolation theory, combined with large-scale physical indoor model test, get some useful conclusions and results:1. When precipitating in aquifer, a single layer of loess land subsidence has completed 60%-70% of the total settlement amount after flow field steady at two days in indoor model tests,when settlement stabilized after precipitation begins it has past around ten days. The ground has a slight rebound after stopping the precipitation, each region there is a big recovery ratio discrete, its average recovery rate of roughly 20%.2. Ground subsidence was positively correlated with precipitation depth and was negativity correlated with the distance from the center of precipitation. Fitting the experimental data analysis shows:when the initial water line for-15cm and the precipitation depth from -45cm to -55cm, the radius of land subsidence caused by precipitation is 85cm-90cm, equivalent to the depth of precipitationabout three times. Polynomial fit at the sampling rate richer accuracy better than linear fit, despite the polynomial fit has a high correlation coefficient value when the sampling rate is less,when used to estimate the ground subsidence has a large range deviation compared with model test.3. Logging level decreased linearly at the initial stages of precipitation. Each measuring point level description point line is funnel-shaped at the same time when steady seepage field. Each logging level quickly return to the initial state after precipitation stopped. Which reflects the loess has good permeability.4. Stress analysis shows soil’s instantaneous compression deformation and viscous compression during precipitation compression process, respectively corresponding to the ground settlement’s dips segment and creep segment, which reflects the "instantaneous elastic deformation" and viscous characteristics of the soil skeleton compression.5., The stress-strin of land subsidence constitutive model are build based on the viscoelastic theory under the effect of precipitation, it consists of two parts which one part is a Hook spring and another is a Voigt structural model.Finally, the further work which requiring studies were briefly discussed.