Study On Groundwater Dynamic Law And Numerical Simulation Based On Deep Foundation Pit Dewatering

In recent years,with the rapid development of urban construction,the construction of high-rise buildings,underground square and subway is accelerating day by day.Large foundation pits are often excavated,and the foundation pit dewatering is frequent,which leads to the decline of groundwater level,land subsidence and other environmental geological phenomena,and has caused adverse effects on the groundwater environment and urban construction,which has been widely concerned by the society.Especially in Wuhan,where the Quaternary loose layer is river lake facies accumulation,the uneven settlement of buildings and road collapse caused by deep foundation pit dewatering are more obvious.Taking jiuwanfang,Jiangan District,Wuhan,as a typical research area,where deep foundation pit dewatering is frequent and land subsidence is serious,this paper studies the dynamic change law of groundwater level,the prediction and early warning of water level drawdown,and the optimization of groundwater level monitoring well network by using dynamic monitoring and numerical simulation methods.The results can provide technical support for the management department to implement the supervision of urban groundwater.The main achievements are as follows:1.Time series analysis method,descriptive statistics and geostatistics are used to analyze the dynamic variation law and influencing factors of groundwater level under the influence of deep foundation pit dewatering.The results show that the interannual variation law of groundwater level is increasing year by year,and the annual variation law has the characteristics of periodicity and seasonality.The flow direction of the groundwater flow field is mainly from the middle to the surrounding,and the flow direction of the flow field is consistent with that of the annual average groundwater level in dry and wet seasons.The variation range of groundwater flow field varies from year to year.Groundwater level has a strong spatial correlation,and its dynamic changes are mainly driven by hydrogeological conditions and deep foundation pit dewatering.2.Through numerical simulation,the prediction and early warning of groundwater level drawdown under the influence of deep foundation pit dewatering are studied.The results show that the model after multiple checks can reflect the actual working conditions.The sensitivity of specific storativity to the model is slightly greater than the hydraulic conductivity.The pumping capacity of two typical periods is 1.70×10~5m~3?1.73×10~5m~3.For every 25%increase in pumping capacity,the maximum increase in drawdown is 0.6 m for the well nearest to the pumping point and 0.1 m for the well farthest from the pumping point.The water level drawdown of0.6 m or above occurred continuously in 15 days for two or more monitoring wells with early warning value of monitoring well pattern.3.According to the dynamic change law of groundwater level and groundwater model,this paper discusses the spatial location traceability of dewatering points and the optimal design of groundwater level monitoring network under the influence of deep foundation pit dewatering.The combination of Kriging interpolation and numerical simulation can be used to optimize the monitoring well pattern concisely and effectively.The method is used to optimize the monitoring well pattern in the study area,and two redundant wells are removed.The Kriging variance is between 0.2 and 0.4.