西安地铁施工基坑降水与地面沉降规律研究

发布时间：2018-05-12 20:04

本文选题：黄土基坑 + 瞬态渗流　；参考：《西安建筑科技大学》2015年硕士论文

【摘要】：近年来,黄土地区城市兴建产生的黄土基坑问题越来越多,本文结合西安地铁三号线大雁塔站主体结构基坑工程,运用瞬态渗流理论对黄土基坑降水及降水对沉降的影响进行了数值模拟,并与现场监测数据进行了对比分析。主要内容如下:(1)黄土层中含水量增加能够降低黄土的强度继而降低黄土基坑的整体稳定性,基坑的安全性降低,为了保证开挖的安全性,故需要在基坑的开挖过程中采取措施降低地下水位。(2)运用瞬态渗流理论对西安地铁三号线大雁塔站主体结构基坑工程的降水过程及降水对沉降的影响进行动态模拟。结果表明:靠近止水帷幕底部的基坑外节点水头变化最大,并且在前一周变化幅度较大,随后变化速度平缓,水头随时间大致呈线性变化,规律与现场水位观测数据较接近。基于比奥固结原理,计算了实际工程降水引起的沉降,沉降值与监测值相差较小。降水20天后,距基坑5m处沉降计算值为2.36cm,实际监测值为2.69cm。(3)运用瞬态渗流理论研究了止水帷幕的作用效果以及管井与止水帷幕的距离对降水效果的影响。结果表明:坑外侧地下水绕过止水帷幕从其底部进入管井,从而延长了渗流路径。设置止水帷幕可大幅降低坑外侧水头损失,进而有效减小固结沉降。降水20天后,由上至下基坑外各观测节点水头损失,距离越大坑外水头损失越小,对于减小固结沉降越有利。
[Abstract]:In recent years, there are more and more problems of loess foundation pit caused by urban construction in loess area. This paper combines with the excavation of the main structure of Dayan Pagoda Station on Xi'an Metro Line 3. The transient seepage theory is used to simulate the influence of dewatering and precipitation on the settlement of loess foundation pit, and the results are compared with the field monitoring data. The main contents are as follows: (1) the increase of water content in the loess soil layer can reduce the strength of loess and then reduce the overall stability of loess foundation pit, and the safety of foundation pit is reduced, in order to ensure the safety of excavation, Therefore, it is necessary to take measures to reduce the groundwater level during the excavation of the foundation pit.) the transient seepage theory is used to simulate the dewatering process and the influence of the precipitation on the settlement of the main structure foundation pit of Dayan Tower Station of Xi'an Metro Line No. 3. The results show that the outside nodal head of the foundation pit near the bottom of the waterproof curtain has the largest change, and the variation range is large in the previous week, then the change speed is gentle, the water head changes linearly with time, and the law is close to the field water level observation data. Based on the Bio consolidation principle, the settlement caused by actual engineering precipitation is calculated, and the difference between the settlement value and the monitoring value is small. After 20 days of precipitation, the calculated value of settlement is 2.36 cm and the actual monitoring value is 2.69 cm. 3) the effect of the waterproof curtain and the distance between the pipe well and the waterproof curtain on the effect of precipitation are studied by using the transient seepage theory. The results show that the underground water at the outside of the pit bypasses the curtain and enters the pipe well from the bottom, thus prolonging the seepage path. Water-stop curtain can greatly reduce the head loss of the outside of the pit, and then effectively reduce the consolidation settlement. After 20 days of precipitation, the head loss of the observation nodes outside the foundation pit from top to bottom is reduced, the larger the distance is, the smaller the head loss is outside the pit, which is more favorable to reduce the consolidation settlement.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU753.66;TU433

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