深基坑流砂质地层轻型井点降水技术研究

发布时间：2018-09-13 11:16

【摘要】：目前大量基坑因地下水位较高,在进行土方开挖后,动水压力改变,坑内外水位差大,较易产生潜蚀、流砂、管涌等渗透破坏现象,从而引起上部及周边地层下沉、塌方;越排水,塌方越严重。因此,如何处理好基坑地下水是摆在每个土建工程师面前的一大难题。本文以轻型井点降水法为研究对象,在掌握国内外基坑降水方法的基础上,简要叙述了常用的基坑降水方法,对轻型井点降水的通病做了综合性的描述;着重分析了轻型井点降水法的基本原理、施工工艺和特点,提出了针对性的防治措施和技术改进新思路,并对其在工程中的应用进行了初步研究。基于芜湖碧桂园镜湖春色二期基坑处于流砂质地层、开挖面积不大、低水位、周围沉降要求严格的状况,提出了采用轻型井点降水技术解决电梯井基础的流砂问题。本降水工程沿电梯井一周布置环形井点系统,共计37个轻型井点,利用四套抽水设备全天候作业。降水期间,及时记录降水量和地下水位高程,并绘制降水量和地下水位高程随时间变化的Q-t图、H-t图,适当调节流量控制阀。同步监测基坑围护桩水平位移和周围建筑物及道路沉降,利用监测数据绘制位移和沉降随时间变化的s-t图,分析降水效果。通过对降水量、地下水位高程、位移和沉降与时间关系图的分析,发现地下水位已降到-11.7m以下,满足设计要求;基坑围护桩累计水平位移5～6mm,远小于预警值30mm;周围建筑物及道路累计沉降1～2mm,均未超过预警值5mm,稳定状况良好;地表3～5mm微小裂痕属正常变化,基坑是稳定安全的。实践证明,在本基坑中使用轻型井点降水效果良好,监测预警方案可行。
[Abstract]:At present, because of the high groundwater level in a large number of foundation pits, the dynamic water pressure changes after earthwork excavation, the difference of water level inside and outside the pit is great, and it is easy to produce seepage damage phenomena such as submersible erosion, quicksand, piping and so on, thus causing the subsidence and collapse of the upper and peripheral strata. The more drainage, the more serious the collapse. Therefore, how to deal with groundwater in foundation pit is a difficult problem for every civil engineer. In this paper, the light well point dewatering method is taken as the research object, on the basis of mastering the domestic and foreign foundation pit dewatering methods, the commonly used foundation pit dewatering methods are briefly described, and the common problems of light well point dewatering are comprehensively described. The basic principle, construction technology and characteristics of light well point dewatering method are emphatically analyzed. New ideas for prevention and control measures and technical improvement are put forward, and its application in engineering is preliminarily studied. Based on the fact that the second phase foundation pit of Jingcheng Lake in Wuhu Bigui Lake is located in a flowing sand layer, the excavation area is small, the water level is low and the settlement requirement is strict, the light well point dewatering technique is proposed to solve the problem of moving sand in elevator well foundation. In this dewatering project, a circular well point system is arranged one week along the elevator well, with a total of 37 light well points, and four sets of pumping equipment are used for all-weather operation. During precipitation, the precipitation and the elevation of groundwater level are recorded in time, and the Q-t map of the variation of precipitation and groundwater level with time is drawn, and the flow control valve is adjusted appropriately. The horizontal displacement of foundation pit retaining pile and the settlement of surrounding buildings and roads were monitored synchronously. The s-t map of displacement and settlement with time was plotted by monitoring data, and the effect of precipitation was analyzed. By analyzing the relationship between precipitation, groundwater level elevation, displacement and settlement and time, it is found that the groundwater level has fallen below -11.7 m, which meets the design requirements. The accumulative horizontal displacement of foundation pit retaining pile is 5mm, which is far less than the warning value of 30mm, the accumulative settlement of surrounding buildings and roads is 1mm and 2mm, which is not more than 5mm, and the stability condition is good. The ground surface 3~5mm crack is a normal change, and the foundation pit is stable and safe. Practice shows that the use of light well point dewatering in this foundation pit is effective and feasible.
【学位授予单位】：安徽理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU753.66

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