基于COMSOL流固耦合的软土地层地连墙槽壁塌孔原因分析  

Cause Analysis of Hole Collapse of Groove Wall of Diaphragm Wall in Soft Soil Layer Based on COMSOL Fluid-solid Coupling

作　　者：钟小春[1] 陈冉 刘江涛 张春彬 丰土根 ZHONG Xiaochun;CHEN Ran;LIU Jiangtao;ZHANG Chunbin;FENG Tugen(College of Civil and Transportation Engineering,Hohai University,Nanjing 210000,China;China Railway(Shanghai)Investment Group Co.Ltd.,Shanghai 200126,China)

机构地区：[1]河海大学土木与交通学院,南京210000 [2]中铁(上海)投资集团有限公司,上海200126

出　　处：《河南科学》2023年第3期358-364,共7页Henan Science

基　　金：国家自然科学基金项目资助(52178387,51678217)。

摘　　要：地下连续墙已经成为城市软土地基基坑主要围护结构型式,但普遍存在成槽塌孔、缩孔施工难题.以南京地铁某车站基坑工程连续墙成槽施工出现塌孔事故为背景,基于COMSOL Multiphysics流固耦合模块开展了地下连续墙成槽稳定性的影响因素敏感性和塌孔发生条件的研究.通过COMSOL Multiphysics流固耦合模块中建立的土层破坏面积来直观表现塌孔区域面积.研究表明:泥浆密度和成槽机提升速度是本工程地层连续墙成槽塌孔的重要因素.泥浆密度决定护壁压力大小,成槽机提升速度过快易造成成槽机底部产生一定范围内泥浆压力快速降低,甚至形成地层地下水向槽内的反渗透,增加槽壁塌孔的风险;绘制提升速度v-泥浆密度ρ-塌孔区域面积S三维曲面图,依据破坏面积大小将区域划分为四个危险等级:Ⅰ区为安全区域(S=0)、Ⅱ区为低风险区域(0<S≤2)、Ⅲ区中风险区域(2<S≤5)、Ⅳ区高风险区域(S>5).最后,提出一种软土地层中考虑成槽影响的地下连续墙槽壁稳定性的评价方法:根据泥浆密度和成槽机提升速度初步判断危险等级.Underground diaphragm wall has become the main retaining structure type of the foundation pit in urban soft soil foundation,but the problems of slotted hole collapse and shrinkage hole in the construction generally exist.In this paper,based on COMSOL Multiphysics fluid-solid coupling module,the sensitivity of influencing factors on the stability of underground diaphragm wall trenching and the occurrence conditions of hole collapse are studied in the context of a hole collapse accident in the construction of diaphragm wall trench in a foundation pit project of a subway station in Nanjing.The area of the collapsed hole area is visually represented by the soil layer failure area established in the fluid-solid coupling module of COMSOL Multiphysics.The research shows that the mud density and the lifting speed of the grooving machine are important factors for the hole collapse of the continuous wall trenching in soil layer of this project.It can be concluded that the mud density and the lifting speed of the trencher are the main factors affecting the damage area of the soil layer.The mud density determines the pressure of the wall protection.If the lifting speed of the trencher is too fast,it can easily cause a rapid reduction of the mud pressure within a certain range at the bottom of the trencher and even form the reverse osmosis of the formation groundwater into the groove,which increases the risk of hole collapse of the groove wall.The three-dimensional surface map of the lifting speed v-mud densityρ-area of hole collapse S is drawn.The area is divided into four risk levels according to the size of the damage area:zoneⅠis the safe zone(S=0),zoneⅡis the low-risk zone(0<S≤2),zoneⅢis the medium-risk zone(2<S≤5),and zoneⅣis the high-risk zone(S>5).Finally,an evaluation method for the stability of underground diaphragm wall considering the influence of groove formation in soft soil layer is proposed,which is to judge the danger grade according to mud density and lifting speed of groove forming machine.

关 键 词：地下连续墙 数值模拟 槽壁稳定 影响因素 

分 类 号：TU43[建筑科学—岩土工程]