Foundation Pit Dewatering Settlement Deformation Caused By Temporal Variations And Precipitation Control

The foundation pit effects on the surroundings is firstly discussed in detail, and the bad phenomena caused by pit dewatering is emphatically analyzed in this paper. Summarization of the settlement induced by dewatering is also displayed. Because that the dewatering ground settlement is the result of the drawdown and soil effective stress increase, this paper gives the water lever dynamic simulation of foundation pit. The math model of groundwater flow of foundation pit with water- resistance curtains is put forward especially with the by-pass seepage coupling of virtual wells. Referring to the Forchheimer's discharge formula, it is deduced and proposed that the formula for radius of drawdown influence with water-resistance curtains. Aiming at the matter of fact that the total stress is deemed changeless as calculating effective stress, the formula for effective stress with changeable total stress is proposed in soils of the confined and unconfined aquifers. The concept of holding water density of soil is brought forward to donate the soil density after dewatering. The function between soil holding water density and hydrogeology concept: specific yield, soil physical mechanics index is deduced, and applied to the FEM calculation of consolidation settlement. As the observed settlement data is the sum value caused by drawdown and bracing structure displacement, the settlement evaluating method is summed up. The gray theory is applied to the evaluating the displacement of bracing structure. It is discussed that the effects and influence of injection wells and is believed that the injection wells effects is better as preventing settlement measure than as harnessing settlement measure. When water levels recover naturally, the checking computations of the groundwork floating resistance should be taken. The concept of dewatering optimum design controlled by surroundings settlement is put forward, that is the design must meet neither the project safety and construction conditions requires nor the surroundings minimal settlement need. This concept will change the traditional ideal that focuses on the safety and construction conditions to also concern the surroundings capability. In the end of this paper, the calculated results are compared with the observed value in one example foundation pit, and are in good agreement with the observed results in which settlement reduced by bracing displacement is already knocked off.