某基坑内积水及桩间土坍塌问题原因分析与治理  

Cause Analysis and Treatment of Water Accumulation and Soil Collapse Between Piles in a Foundation Pit

作　　者：齐永国[1] QI Yongguo(China Railway Siyuan Survey and Design Group Co.Ltd.,Wuhan Hubei 430063,China)

机构地区：[1]中铁第四勘察设计院集团有限公司,湖北武汉430063

出　　处：《铁道建筑技术》2023年第6期37-40,共4页Railway Construction Technology

基　　金：国家自然科学基金项目(51609204)。

摘　　要：针对张家港某工程基坑内严重积水及桩间土坍塌问题,从地质、设计、施工等影响因素开展分析,根据降水监测数据和设计经验,研究降水井设计缺陷,分析高压旋喷桩止水帷幕试桩资料,找出桩间土坍塌与坑内积水症结所在,并提出相应解决措施。研究结论:(1)如地层为粉砂类夹杂粉土、黏土,制定降水方案不仅要依据规范相关条文,更需综合考虑地层成分组成,重视其夹层情况;勘察阶段应开展现场降水试验,为设计提供可靠参数和方案选择。(2)基坑围护结构桩间土渗透破坏往往因提前采取加固措施而被忽略,一旦形成水力坡降,易导致流土甚至土体坍塌。因此,基坑围护和止水帷幕设计施工时,应避免土体渗流通道形成。(3)不同地层施工高压旋喷桩,应注重前期试桩工作,获取合理技术参数并在施工阶段合理应用;施工过程应注意垂直度和障碍物处理,重视排桩支护桩间土防护,并及时挂网喷混,设置导流管。In view of the serious water accumulation in a foundation pit in Zhangjiagang and the collapse of soil between piles,the paper analyzes the geology,design,construction and other influencing factors,studies the design defects of the dewatering well according to the dewatering monitoring data and relevant design experience,analyzes the pile test data of the high-pressure jet grouting pile water stop curtain,finds out the crux of the problem of ponding in the pit and soil collapse between piles,and proposes corresponding solutions.Research conclusions:(1)When the stratum is composed of silty sand mixed with silt and clay,the formulation of the dewatering plan should not only be based on the relevant provisions of the specification,but also take into account the composition of the stratum and pay attention to its interlayer.At the survey stage,regular on-site precipitation test shall be carried out to provide reliable parameters and scheme selection for the design.(2)The seepage damage of the soil between piles of the foundation pit retaining structure is often ignored because of the reinforcement measures.Once the hydraulic gradient is formed,it will lead to the flow of soil and even the collapse of the soil.Therefore,the formation of the seepage passage of the soil should be avoided during the design and construction of the foundation pit retaining and water stop curtain.(3)During the construction of high-pressure rotary jet grouting piles in different strata,attention should be paid to the preliminary pile test work to obtain reasonable technical parameters and reasonable application in the construction stage.During the construction process,attention should be paid to the treatment of verticality and obstacles,and attention should be paid to the protection of soil between piles for row pile support.In addition,the net should be hung in time for shotcrete,and the diversion pipe should be set.

关 键 词：基坑积水 桩间土坍塌 降水井设计 水力梯度 处理措施 

分 类 号：TU470[建筑科学—结构工程]