Effect of retaining wall leakage on the deformation behavior of foundation pit in water-rich sandy strata
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摘要:
针对深基坑漏水漏砂引发的灾害问题,探究基坑渗漏灾害发展规律及其控制方法对地下工程施工安全具有重要意义。结合某富水砂层排桩深基坑渗漏灾害实例,阐释了基坑漏水漏砂灾害发展特征及诱发原因,并采用现场监测和数值模拟方法对局部渗漏水下基坑变形性状及其控制措施进行了研究。研究结果表明:(1)基坑渗漏灾害发展是一个复杂的多场耦合作用过程,具有一定的隐蔽性和突发性;(2)挡墙水平位移曲线分布发展过程为“斜线”形—“锅底”形—浅“倒V”形—深“倒V”形,渗漏后挡墙最大水平位移为渗漏前的1.29~1.44倍;(3)墙后地表沉降曲线分布发展过程为“平勺底”形—“浅勺底”形—“深勺底”形,沉降槽敏感区范围为1.00he ~1.20he(he为开挖深度),局部渗漏引起地表沉降槽加深变宽,渗漏后最大地表沉降为渗漏前的1.16~1.65倍;(4)地下水位“跳跃式”波动变化特征可作为评判基坑渗漏灾害的前兆信号;(5)支撑轴力变化随基坑开挖与支护过程动态调整从而协调变形发展,在基坑发生渗漏过程中支撑轴力出现小幅波动。采取“注浆+高压旋喷桩”联合处治措施可有效应对富水砂层基坑渗漏灾害控制难题,研究成果可为基坑工程渗漏灾害理论研究与控制提供参考。
Abstract:Aiming at the disaster problem caused by leakage of water and sand in deep excavation, it is of great significance to reveal the evolution of foundation pit leakage disaster and its control method for underground engineering construction safety. Based on the leakage disaster of row-pile retaining deep foundation pit induced by deep excavation in water-rich sandy strata, the development characteristics and causes of leakage of water and sand during construction were analyzed, and the deformation behavior of foundation pit and its control measures under partial leakage were investigated by field monitoring and numerical simulation method. The results show that the development of leakage disaster of foundation pit is a complicated multi-field coupling process, and its occurrence is hidden and sudden. The horizontal displacement curve of retaining wall successively transformed from “oblique” shape, “bottom of pot” shape, shallow “inverted V” shape to deep “inverted V” shape with excavation depth. The maximum horizontal displacement of the retaining wall after leakage is 1.29 to 1.44 times larger than before leakage. The ground settlement curve of behind the retaining wall successively transformed from “flat ladle bottom” shape, “shallow ladle bottom” shape to “deep ladle bottom” shape with excavation depth; the sensitive zone of settlement trough is 1.00he to 1.20he (he is excavation depth). The ground settlement trough deepens and widens due to partial leakage, and the maximum ground settlement after leakage is 1.16 to 1.65 times that before leakage. The characteristics of the “jump” fluctuation of groundwater level can be used as the precursor signal to judge the leakage disaster of foundation pit. The change of supporting axial force is dynamically adjusted with the process of excavation and support to coordinate the development of deformation, and the supporting axial force fluctuates slightly during retaining wall leakage. The combined treatment measures of grouting and high pressure rotating spouting pile can effectively deal with the problem of leakage disaster control of foundation pit in water-rich sandy strata. This study can provide basic information for the theoretical analysis and control of leakage disaster of foundation pit.
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随着城市地下工程的快速发展,涌现出大量的“深、大、难”深基坑工程[1 − 3],地下深开挖引起的工程灾害频繁发生[4],其中基坑渗漏灾害问题[5 − 6]尤为凸显。工程实践表明,基坑渗漏灾害主要是由地下水渗流引起的水土流失诱发的,其发生过程具有突发性、隐蔽性、复杂性以及高危害性等显著特点,严重威胁着城市的正常生产和人民的生命安全。因此有必要对基坑渗漏灾害问题进行系统深入的研究,以实现灾害预测与防控的目的,为城市地下工程大规模建设提供理论基础和技术支撑。
目前,针对深基坑工程渗漏灾害及控制问题,国内外学者通过采用实例分析、模型试验和数值模拟等方法对基坑渗漏问题进行了一定的研究。在实例分析方面,Ni等[7]、Koref等[8]、Wu等[ 9]分析了基坑漏水漏砂灾害发展过程和变形破坏特征,指出基坑局部渗漏引起周围土体流失和地表塌陷等灾害;Jo等[10]采用现场观测、探地雷达探测等多种手段,对开挖深度为38 m的冲积土层深基坑渗漏事故进行了分析;Liu等[11]、樊东东等[12]通过统计分析指出,地连墙钢筋裸露、接缝缺陷、墙体局部外鼓和复杂的水文地质条件是基坑渗漏的主要诱因;蒋锋平等[13]结合实例分析了地连墙渗漏引起的地表沉降特征,认为地连墙施工不当和接缝处理不当是导致地连墙发生渗漏的重要诱因;张瑾等[14]基于实测数据发现,基坑渗漏引起主动区土压力增大是导致墙体变形突变的主要原因,且周围土体变形存在滞后性;Tan等[15]通过对上海地铁基坑渗漏事故分析,发现渗漏引起坑外地表沉降可达42 mm,并提出采用高压旋喷桩和搅拌桩可有效封堵渗流通道;张正等[16]、李义堂[17]、郑刚等[18]给出采取地面垂直注浆封堵、桩间注浆固结、钢板封闭和快速封底等处治基坑渗漏的有效建议。在模型试验方面,郑刚等[19]设计了一种可以改变缝隙宽度的砂、水渗漏可视化试验装置,研究了地下工程漏水漏砂灾害发展规律;李波等[20]通过离心模型试验表明地连墙渗漏导致地表沉降量和沉降范围明显增大;曹卫平等[21]通过模型试验分析了土体渗漏对砂土基坑的影响规律,指出土体渗漏对基坑周边环境产生严重危害,并建议采取堆土反压措施防止基坑变形加剧。在数值模拟方面,胡琦等[22]借助有限元软件建立了基坑渗漏渗透破坏平面应变模型,分析了粉砂地基基坑渗透破坏模式;郭景琢等[23]基于MODFLOW数值计算模型,揭示了渗漏条件下基坑坑外水位与渗流场的时空演变规律;戴轩等[24]采用DEM-CFD耦合方法模拟基坑渗漏,揭示了基坑工程漏水漏砂引起的地层运移规律;WU等[25 − 26]进一步建立了基坑渗漏三维流固耦合分析模型,研究结果表明漏水引起的地表沉降变化与漏水点位置、渗水量、土渗透性等因素密切相关;在此基础之上,江杰等[27]应用三维流固耦合数值模型,分析了渗漏条件下预降水对基坑变形的影响;晁慧等[28]建立了基坑渗漏三维DEM-CFD耦合数值分析模型,指出地连墙渗漏会引起渗漏点附近主动水土压力突增5.7~8.5倍,且地连墙渗漏会引发地墙结构断裂、坑外地表突沉以及踢脚破坏风险。
综上所述,现有的研究涉及到不同区域土质、结构型式和开挖深度条件下基坑渗漏事故原因、变形性状及控制措施等方面,为基坑渗漏研究及灾害防治提供了有益的指导。然而,由于基坑渗漏过程的复杂性和地质条件的差异性,对于不同支护方式、不同地质条件下的基坑渗漏特征及其灾变机理还未完全掌握,相关实例数据和处治经验有待进一步积累,尤其是富水砂层深基坑工程。鉴于此,本文以某城市地铁车站深基坑工程为研究背景,分析基坑漏水漏砂灾害发展过程及诱发因素,揭示基坑渗漏对挡墙水平位移、墙后地表沉降、坑外地下水位和支撑水平轴力的影响规律,并给出富水砂层基坑施工过程中渗漏灾害的控制措施。
1. 工程背景
1.1 基坑概况
某城市地铁车站长条形深基坑工程,车站主体为地下两层现浇钢筋砼箱型结构,基坑长470.0 m、宽23.1 m、深18.0 m,上覆土层厚度2.34~3.26 m,车站采用明挖顺作法施工。基坑试验段端头井开挖深度为16.73~17.87 m,标准段开挖深度为15.50~16.41 m,基坑支护系统采用钢筋砼钻孔灌注桩+三轴搅拌桩止水帷幕+内支撑的型式(图1)。其中,钻孔灌注桩尺寸为ϕ
1000 mm@1200 mm,桩长23.0 m,桩墙外侧为ϕ850 mm@600 mm、深度20.0 m的三轴搅拌桩止水帷幕,围护桩与搅拌桩间隙采用双液注浆加固,增强围护结构止水功能。端头井基坑沿深度方向设置4道横向水平支撑,第1道为梁式钢筋砼支撑(0.8 m×1.0 m,间距9 m),第2、3、4道采用钢管支撑(直径609 mm,壁厚16 mm,间距3 m)。1.2 地质条件
拟建场地地层主要为全新统人工填土(Qhml)和冲积层(Qhal),以及古近系新余群(EX)基岩。场地土层自上而下依次为:①2素填土,层厚1.0~4.8 m;②1粉质黏土,褐黄色,以粉黏粒为主,局部夹薄层粉砂,层厚0.3~3.0 m;②2粉砂,棕黄色,层厚0.5~9.0 m;②4中砂,灰白、灰黄色,层厚0.5~5.0 m;②5粗砂,灰白色,层厚1.0~7.4 m;②6砾砂,灰白色,层厚2.5~6.0 m;⑤1强风化泥质粉砂岩,层厚0.4~2.3 m;⑤2中风化泥质粉砂岩,层厚6.4~10.6 m;⑤3微风化泥质粉砂岩,最大揭露层厚11.0 m。基坑开挖深度范围主要为砂性土层,平均渗透系数为10−3~10−2 cm/s,地下水主要为赋存于砂砾层中的孔隙潜水,埋深为4.1~6.5 m,地下水位变化受降雨和临近江水影响显著。各岩土层主要物理力学参数详见表1。表中,h为岩土层厚度,γ为岩土体容重,c为黏聚力,φ为内摩擦角,K为渗透系数,Es为压缩模量,ν为泊松比。
表 1 场地土层主要物理力学性质参数Table 1. Main physical and mechanical parameters of soil layers岩土类别 h/m γ/(kN·m−3) c/kPa φ/(°) K/(cm·s−1) Es/MPa ν ①2素填土 1.0~4.8 17.0 3.0 10.0 2.00×10−4 5.00 0.30 ②1粉质黏土 0.3~3.0 18.7 19.3 18.0 4.00×10−5 9.56 0.34 ②2粉砂 0.5~9.0 17.9 10.8 30.0 0.80×10−3 11.30 0.34 ②4中砂 0.5~5.0 18.5 0 35.0 1.20×10−2 14.40 0.31 ②5粗砂 1.0~7.4 19.0 0 38.0 6.00×10−2 15.80 0.31 ②6砾砂 2.5~6.0 19.5 0 40.0 8.00×10−2 19.70 0.30 ⑤1强风化泥质粉砂岩 0.4~2.3 21.0 50.0 23.0 2.48×10−6 600.00 0.34 ⑤2中风化泥质粉砂岩 6.4~10.6 24.3 600.0 35.0 4.50×10−7 1500.00 0.34 ⑤3微风化泥质粉砂岩 — 24.7 800.0 40.0 3.00×10−8 2500.00 0.28 1.3 监测方案
为全面掌握基坑开挖对挡墙变形和周围环境的影响,分别对挡墙水平位移、墙后地表沉降、坑外地下水位和坑内支撑轴力进行动态监测,测点平面布置如图2所示。其中,排桩挡墙水平位移布设40个测斜点,分别记为CX-1—CX-40,累计位移报警值不超过0.20%he(he为开挖深度),且不大于20.0 mm,变化速率不超过3.0 mm/d;沿基坑周边间隔25.0 m布设40个墙后地表沉降监测断面,每个断面设5个监测点,分别记为DS1-i—DS40-i(i为测点编号),累计沉降报警值不超过30.0 mm,变化速率不超过3.0 mm/d;沿基坑周边间隔50.0 m布设24个坑外地下水位监测点,分别记为SW-1—SW-24,地下水位累计变化报警值不超过±1.0 m,变化速率不超过±0.5 mm/d;在坑内间隔50.0 m分层布设14个内支撑水平轴力监测点,分别记为ZLm-1—ZLm-14(m为支撑层数),支撑轴力报警值不超过0.8倍设计值。基坑开挖期间监测频率为3天1次,特殊情况下监测频率可适当调整。
基坑采用“明挖顺筑、竖向分层、纵向分段、先撑后挖”的开挖方式,端头井共分5层进行开挖,开挖深度依次为2.0,7.5,11.0,15.0,17.9 m,开挖前坑内降水后地下水位应低于基坑底面0.5 m,基坑开挖至坑底标高后,依次施作混凝土垫层、底板等结构。
2. 挡墙渗漏灾变过程
在北端头井基坑开挖至坑底15.0~17.9 m时,围护桩桩间发生局部漏水、漏砂现象(图3、图4),呈现渗漏速度快、流量大的特点,并在渗漏位置对应断面地表发生瞬时塌陷,随后坑底漏水、漏砂速度减缓,地表下陷也逐渐减慢直至停止。其中,第1次渗漏发生在端头井西侧,渗漏点位置距地表深16.0 m,在距基坑围护结构边沿1.5 m处发生地表塌陷,形成的塌陷区域长、宽、深分别为8.0,5.0,3.5 m(图3a),流砂量为126.0 m3;第2次渗漏发生在端头井东侧,渗漏点位置距地表深17.0 m,在距基坑围护结构边沿0.3 m处发生地表塌陷,形成的塌陷区域长、宽、深分别为8.0,4.0,2.5 m,流砂量为75.0 m3。对比前后2次渗漏情况发现,渗漏位置均发生在北端头井长边方向、深度为第4道支撑与坑底之间;渗漏以单点形式存在,不具有连续性,且渗漏点位置同处一个断面;基坑漏水漏砂持续时间为3~5 min,具有突发性、瞬时性,且地表沉陷伴随基坑漏水漏砂而发生。
根据现场调查与测试分析表明,本基坑发生漏水漏砂灾害的主要原因为:①地质条件,基坑开挖深度范围内主要为深厚富水砂层,砂性土层厚为10.0~15.0 m,且较为松散,见图3(b);②水力条件,地下水位埋深较浅,埋深为4.0~6.5 m,水位变化受大气降雨和临近江水影响显著,基坑坑内降水开挖与持续降雨气候条件加剧坑内外地下水水头差,加之砂性地层条件,极易引起基坑发生渗透破坏;③止水帷幕质量缺陷,排桩围护结构与止水帷幕之间、钻孔灌注桩之间存在0.2 m的间隙(图4b),该间隙虽采用双液注浆增强止水作用,但仍有可能成为基坑渗漏的水力通道;止水帷幕桩现场钻芯取样发现,岩芯局部较破碎,且可见未完全固结泥砂,在砂层与泥质粉砂岩层界面上下一定深度范围桩体存在微张裂隙或裂隙间局部夹裏少量泥砂的现象,此区域为高水土压力作用下止水帷幕发生破坏、产生局部渗漏的薄弱点;④止水帷幕局部大变形伤损,基坑开挖引起刚度相对较小的水泥土帷幕结构大变形,局部因张裂而出现渗漏水,在高水土压力环境下水力损伤效应加剧,进而导致隔水作用失效。
3. 现场实测结果分析
由于基坑渗漏打破了支护结构、周围地层原有的应力平衡状态,引起基坑的受力和变形特征与常规施工条件下存在显著差异。考虑本基坑工程挡墙结构局部渗漏影响,对基坑排桩水平位移、墙后地表沉降、坑外地下水位以及支撑水平轴力变化规律进行对比分析,阐释挡墙渗漏对支护结构受力、变形和周围环境的影响,从而为富水砂层基坑支护结构设计与灾害防治提供借鉴。
3.1 渗漏水对挡墙水平位移的影响
图5为不同工况下排桩挡墙水平位移曲线分布特征。由图可得,随着基坑开挖深度增加,挡墙水平位移显著增大,其分布曲线呈“鼓肚”形;当基坑开挖至坑底时,测点CX-2(北端头井短边方向)、CX-3(北端头井长边方向)挡墙最大水平位移分别为5.25,11.92 mm;当基坑发生局部渗漏后,测点CX-2、CX-3挡墙最大水平位移分别为6.75,17.16 mm,相较于渗漏前分别增加了28.57%、43.96%;当基坑底板浇筑完成后,测点CX-2、CX-3挡墙最大水平位移分别为5.45,19.55 mm,相较于渗漏前分别增加了3.81%、64.01%;测点CX-2与测点CX-3对比可知,基坑局部渗漏会加剧挡墙水平位移,且受基坑尺寸和坑角效应的影响[29 − 30],局部渗漏下基坑长边方向挡墙水平变形大于短边方向。主要原因可能有:①基坑发生渗漏引起桩后水土流失,导致挡墙遭受附加动水荷载的冲击作用;②基坑渗漏延误工期,使得未形成封闭的围护结构暴露时间增长,挡墙变形的时间效应突显;③桩后注浆加固和地表大体量素混凝土回填,以及注浆加固后地下水位因降雨迅速回升,导致桩后水土压力增大。
上述分析表明,基坑局部渗漏对围护结构和周围地层变形具有重要影响。为此,借助PLAXIS2D建立考虑渗流作用的砂土-止水帷幕-排桩挡墙有限元计算模型,模拟基坑降水开挖和围护结构局部渗漏条件,对局部渗漏条件下排桩挡墙变形和墙后地表沉降进行计算分析。结合端头井段深基坑实际,取基坑开挖尺寸为深度17.9 m、宽度23.0 m,开挖深度范围主要为黏性土层和砂性土层。考虑模型的对称性后取1/2模型进行计算,建立的数值计算模型尺寸为高度35.0 m、宽度60.0 m(图6),模型共计1 789个单元,14 503个节点。在数值模拟计算中,岩土层采用实体单元模拟,假定地基土层厚度沿水平方向均匀分布,土体为均质、各向同性材料,材料服从土体硬化模型(HS模型)[31 − 33],各土层计算参数取值详见表1和表2。排桩挡墙和内支撑采用结构单元模拟,止水帷幕采用实体单元模拟,材料均服从线弹性本构模型,其计算参数取值为:止水帷幕重度为20.0 kN/m3,黏聚力为120.0 kPa,内摩擦角为40.0°,弹性模量为0.4 GPa,泊松比为0.25;挡墙重度为25.0 kN/m3,弹性模量取31.5 GPa,泊松比为0.2;混凝土支撑重度为25.0 kN/m3,弹性模量取30.0 GPa,泊松比为0.2;型钢支撑重度为78.0 kN/m3,弹性模量取210.0 GPa,泊松比为0.3。本模型中通过在挡墙结构上预设渗漏通道来实现局部渗漏水的模拟,渗漏点距坑底0.9 m,尺寸为0.2 m×0.2 m,渗漏区域实体单元渗透系数为8.00×10−2 cm/s。
表 2 土体硬化模型材料参数Table 2. Materials parameters of hardening soil model土层类型 vur pref/(kN·m−2) Rf m ψ/(°) Rint ①2素填土 5.0 5.0 25.0 0.30 100 0.9 0.5 0.0 0.65 ②1粉质黏土 9.6 9.6 47.8 0.34 100 0.9 0.5 0.0 0.65 ②2粉砂 11.3 11.3 33.9 0.34 100 0.9 0.5 3.0 0.70 ②4中砂 14.4 14.4 43.2 0.31 100 0.9 0.5 3.0 0.70 ②5粗砂 15.8 15.8 47.4 0.31 100 0.9 0.5 5.0 0.70 ②6砾砂 19.7 19.7 59.1 0.30 100 0.9 0.5 5.0 0.70 注: 为三轴排水试验的割线刚度, 为固结试验的切线刚度, 为卸荷再加荷模量,vur为卸荷再加荷泊松比,pref为参考应力(一般取100 kPa),Rf为破坏比,m为刚度应力水平相关幂指数,ψ为剪胀角,Rint为界面单元强度折减系数。图7为排桩挡墙水平位移数值计算值与实测值对比。由图可知,挡墙水平位移曲线数值计算结果与实测结果发展趋势基本一致,挡墙水平位移曲线随基坑开挖深度呈渐进发展过程,其发展过程可描述为“斜线”形—“锅底”形—浅“倒V”形—深“倒V”形;各工况下挡墙最大水平位移计算值分别为0.91,9.45,12.78,14.60,15.03,15.77 mm,实测值分别为0.77,1.97,5.62,9.36,11.92,17.16 mm,渗漏后挡墙水平位移计算值较渗漏前增加了4.92%;局部渗漏下挡墙最大水平位移计算值与实测值分别为0.09%he、0.10%he,挡墙最大水平位移位置(Hmax)计算值与实测值分别为0.70he、0.73he;计算值与实测值相比,渗漏后挡墙变形均呈增加趋势,但渗漏后挡墙水平位移计算值偏小,原因是数值计算中未能体现渗漏条件下动水荷载对挡墙的冲击作用。
3.2 渗漏水对墙后地表沉降的影响
图8为不同工况下墙后地表沉降曲线分布特征。由图可得,随着基坑开挖深度的增加,地表沉降不断增大呈下凹趋势,开挖深度越大“勺形”凹槽分布越显著,即基坑开挖深度越大,“勺底”越深(沉降量越大),“勺把”越长(影响范围越大);当基坑开挖至坑底时,断面DS2-i(北端头井短边方向)、DS3-i(北端头井长边方向)的最大地表沉降量分别为5.10,9.80 mm;当基坑发生局部渗漏后,断面DS2-i、DS3-i的最大地表沉降量分别为5.90,16.20 mm,相较于渗漏前分别增加了15.69%、65.31%;当基坑底板浇筑完成后,断面DS2-i、DS3-i的最大地表沉降量分别为6.70,17.70 mm,相较于渗漏前分别增加了31.37%、46.28%。基坑渗漏前后对比表明,局部渗漏引起地表沉降槽进一步加深变宽,最大地表沉降量可达渗漏前的1.65倍,且端头井长边方向最大地表沉降量明显大于短边方向。
图9为墙后地表沉降数值计算值与实测值对比。由图可知,墙后地表沉降曲线随基坑开挖由“平勺底”形—“浅勺底”形—“深勺底”形发展;根据墙后地表沉降槽分布特征,地表沉降影响范围可划分为敏感区(Ⅰ区)、过渡区(Ⅱ区)和非敏感区(Ⅲ区),敏感区内地表沉降量最大,其范围为1.00he ~ 1.20he;各工况下墙后最大地表沉降计算值分别为2.19,7.86,10.58,12.15,12.63,30.12 mm,实测值分别为3.20,4.80,6.60,8.40,9.80,16.20 mm,渗漏后地表沉降计算值为渗漏前的2.38倍。由此说明,基坑渗漏会引起墙后地表沉降大幅增加,且对敏感区影响最为显著。
3.3 渗漏水对坑外地下水位的影响
图10为基坑施工期间坑外地下水位及其变化速率时程曲线分布特征。由图可得,在基坑北端头井施工期间,坑外地下水位随基坑开挖过程呈缓慢下降趋势,而后逐步趋于稳定,受持续降雨影响北端头井地下水位出现快速回升;基坑发生渗漏过程中,坑外地下水位急剧下降,地下水位变化速率呈现“跳跃式”变化,其中测点SW-3地下水位累计变化量及变化速率均超过监测报警值;基坑渗漏险情处治后,坑外地下水位变化逐步恢复稳定状态。基坑渗漏水发生、发展过程表明,科学地控制地下水位,全面掌握地下水位动态变化,确保围护结构防渗效果是预防基坑发生渗漏灾害的有效措施。
3.4 渗漏水对坑内支撑轴力的影响
图11为基坑内支撑轴力时程曲线分布特征。由图可得,随着基坑开挖深度增加,坑侧主动土压力逐渐增大,在侧向荷载与内支撑作用下,支撑轴力随时间呈渐进波动式增长而后逐步趋于稳定,第1道支撑轴力稳定的时间为30~60 d,第2、3、4道支撑轴力稳定的时间为15~20 d;端头井第1、2、3、4道支撑轴力值变化范围依次为208~
2124 、 508~1118 、236~660、104~415 kN,各道支撑轴力最大值分别为设计值的0.87,0.75,0.45,0.41倍。由此说明,第1道混凝土支撑主要承担挡墙后土压力荷载,其轴力值较大,而第2、3、4道钢支撑轴力相对较小,钢支撑设计相对偏保守。在基坑发生渗漏过程中,支撑轴力出现小幅波动,北端头井(ZL1-1)和南端头井(ZL1-13)第1道支撑轴力最大值分别为2 124,672 kN,南端头井支撑轴力为北端头井的31.6%,即南端头井第1道支撑轴力明显小于北端头井,主要原因是北端头井出现渗漏灾害后,在南端头井施工过程中对原围护结构采取了强化处治措施。3.5 基坑局部渗漏控制措施及效果
由前述分析可知,基坑开挖施工过程中渗漏灾害的发生机制非常复杂,其具有复杂的灾变演化过程。因此,基坑渗漏灾害防控是一个复杂的、综合的控制工程,其防控思路应从地质环境、围护结构、施工过程三方面重点考虑。针对本工程渗漏灾害发展特征及其诱发因素,采取的处治措施具体为:(1)采用填充、注浆等相结合的方法对渗漏点进行封堵处理,抑制基坑周围土体持续流失和险情扩大;(2)及时对地面塌陷区域进行加固处理,避免墙后脱空而导致围护结构外移或失稳;(3)基坑渗漏水和地面下沉稳定后,在渗漏区域围护结构外侧按照先两端后中间的顺序施作一排ϕ800 mm@600 mm高压旋喷桩(图12a);(4)分层分段开挖渗漏区土方(图12b),并对渗漏点进行封口处理,再在其上挂网喷浆(图13);(5)挂网喷浆终凝后,采用钢花注浆管(ϕ25 mm@300 mm)对挡墙渗漏区进行注浆加固(图13),以保证围护结构隐蔽区域或薄弱结构部位的抗渗能力;(6)待端头井一侧土方开挖完成后,及时施做垫层和底板,以确保基坑整体稳定。
通过采取加固处治措施后,现场实测表明,排桩挡墙水平位移和墙后地表沉降得到有效抑制。同时,采取本方法对后续施工的标准段和南端头井基坑进行了预防加固处治,长期观测发现,排桩挡墙变形、地表沉降和地下水位变化均保持在控制值范围内,且基坑整体防渗效果和稳定性良好。
4. 结论
(1)基坑渗漏灾害发展是一个复杂的多场耦合作用过程,具有一定的隐蔽性和突发性;基坑漏水漏砂灾害灾变过程为“地下水力环境变化→围护结构侧壁出现可见湿斑→围护结构侧壁局部漏水→局部渗漏扩展恶化→围护结构出现渗漏孔洞(贯穿通道)→坑内涌水涌砂→周围地层水土流失(地层损失)→诱发地表塌陷、围护结构过大变形、基坑失稳等其它灾害”。
(2)挡墙水平位移随开挖深度发展过程为“斜线”形—“锅底”形—浅“倒V”形—深“倒V”形分布;局部渗漏下挡墙最大水平位移为0.10%he,挡墙最大水平位移位置为0.73he;渗漏后挡墙最大水平位移为渗漏前的1.29~1.44倍,且端头井长边方向挡墙水平变形大于短边方向。
(3)墙后地表沉降曲线呈“勺形”凹槽分布,其发展过程为“平勺底”形—“浅勺底”形—“深勺底”形;地表沉降影响范围可划分为敏感区、过渡区和非敏感区,敏感区范围为1.00he ~ 1.20he;基坑渗漏引起地表沉降槽加深变宽,渗漏后最大地表沉降为渗漏前的1.16~1.65倍。
(4)基坑发生渗漏前后地下水位波动显著,其“跳跃式”变化特征可作为基坑发生渗漏灾害的前兆信号;坑内支撑轴力变化随开挖深度和支撑施加不断发生调整从而协调变形发展,其演变过程随时间呈波动式渐进增长,在基坑发生渗漏过程中支撑轴力出现小幅波动。
(5)现场实测表明,采取“注浆+高压旋喷桩”联合处治措施可有效应对富水砂层基坑渗漏灾害控制难题;为降低基坑发生渗漏灾害风险,应慎重选型基坑围护结构,保证围护结构施工质量及其防渗效果,尤其是隐蔽、薄弱结构部位,重视并发挥基坑施工监测的反馈和预判作用有利于富水、富砂地层深基坑渗漏灾害防治与控制。
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表 1 场地土层主要物理力学性质参数
Table 1 Main physical and mechanical parameters of soil layers
岩土类别 h/m γ/(kN·m−3) c/kPa φ/(°) K/(cm·s−1) Es/MPa ν ①2素填土 1.0~4.8 17.0 3.0 10.0 2.00×10−4 5.00 0.30 ②1粉质黏土 0.3~3.0 18.7 19.3 18.0 4.00×10−5 9.56 0.34 ②2粉砂 0.5~9.0 17.9 10.8 30.0 0.80×10−3 11.30 0.34 ②4中砂 0.5~5.0 18.5 0 35.0 1.20×10−2 14.40 0.31 ②5粗砂 1.0~7.4 19.0 0 38.0 6.00×10−2 15.80 0.31 ②6砾砂 2.5~6.0 19.5 0 40.0 8.00×10−2 19.70 0.30 ⑤1强风化泥质粉砂岩 0.4~2.3 21.0 50.0 23.0 2.48×10−6 600.00 0.34 ⑤2中风化泥质粉砂岩 6.4~10.6 24.3 600.0 35.0 4.50×10−7 1500.00 0.34 ⑤3微风化泥质粉砂岩 — 24.7 800.0 40.0 3.00×10−8 2500.00 0.28 表 2 土体硬化模型材料参数
Table 2 Materials parameters of hardening soil model
土层类型 vur pref/(kN·m−2) Rf m ψ/(°) Rint ①2素填土 5.0 5.0 25.0 0.30 100 0.9 0.5 0.0 0.65 ②1粉质黏土 9.6 9.6 47.8 0.34 100 0.9 0.5 0.0 0.65 ②2粉砂 11.3 11.3 33.9 0.34 100 0.9 0.5 3.0 0.70 ②4中砂 14.4 14.4 43.2 0.31 100 0.9 0.5 3.0 0.70 ②5粗砂 15.8 15.8 47.4 0.31 100 0.9 0.5 5.0 0.70 ②6砾砂 19.7 19.7 59.1 0.30 100 0.9 0.5 5.0 0.70 注: 为三轴排水试验的割线刚度, 为固结试验的切线刚度, 为卸荷再加荷模量,vur为卸荷再加荷泊松比,pref为参考应力(一般取100 kPa),Rf为破坏比,m为刚度应力水平相关幂指数,ψ为剪胀角,Rint为界面单元强度折减系数。 -
[1] 郑刚,程雪松,周海祚,等. 岩土与地下工程结构韧性评价与控制[J]. 土木工程学报,2022,55(7):1 − 38. [ZHENG Gang,CHENG Xuesong,ZHOU Haizuo,et al. Resilient evaluation and control in geotechnical and underground engineering[J]. China Civil Engineering Journal,2022,55(7):1 − 38. (in Chinese with English abstract)] ZHENG Gang, CHENG Xuesong, ZHOU Haizuo, et al. Resilient evaluation and control in geotechnical and underground engineering[J]. China Civil Engineering Journal, 2022, 55(7): 1 − 38. (in Chinese with English abstract)
[2] 向朱锋,徐金明. 悬挂式止水帷幕条件下深基坑开挖变形特性研究[J]. 水文地质工程地质,2023,50(5):96 − 106. [XIANG Zhufeng,XU Jinming. Deformation characteristics of deep foundation pit with suspended waterproof curtain during excavation[J]. Hydrogeology & Engineering Geology,2023,50(5):96 − 106. (in Chinese with English abstract)] XIANG Zhufeng, XU Jinming. Deformation characteristics of deep foundation pit with suspended waterproof curtain during excavation[J]. Hydrogeology & Engineering Geology, 2023, 50(5): 96 − 106. (in Chinese with English abstract)
[3] 胡长明,林成. 黄土深基坑潜水区降水诱发地面沉降的简化算法[J]. 中国地质灾害与防治学报,2021,32(3):76 − 83. [HU Changming, LIN Cheng. Simplified calculation of settlement due to dewatering of phreatic aquifer in loess area[J]. The Chinese Journal of Geological Hazard and Control,2021,32(3):76 − 83. (in Chinese with English abstract)] HU Changming, LIN Cheng. Simplified calculation of settlement due to dewatering of phreatic aquifer in loess area[J]. The Chinese Journal of Geological Hazard and Control, 2021, 32(3): 76 − 83. (in Chinese with English abstract)
[4] 蒋涛,崔圣华,冉耀. 开挖和降雨耦合诱发滑坡机理分析——以四川万源前进广场滑坡为例[J]. 中国地质灾害与防治学报,2023,34(3):20 − 30. [JIANG Tao, CUI Shenghua, RAN Yao. Analysis of landslide mechanism induced by excavation and rainfall: A case study of the Qianjin Square landslide in Wanyuan City, Sichuan Province[J]. The Chinese Journal of Geological Hazard and Control,2023,34(3):20 − 30. (in Chinese with English abstract)] JIANG Tao, CUI Shenghua, RAN Yao. Analysis of landslide mechanism induced by excavation and rainfall: A case study of the Qianjin Square landslide in Wanyuan City, Sichuan Province[J]. The Chinese Journal of Geological Hazard and Control, 2023, 34(3): 20 − 30. (in Chinese with English abstract)
[5] 刘俊城,谭勇,宋享桦,等. 富水砂土基坑渗水对侧墙变形和周边环境的影响[J]. 浙江大学学报(工学版),2023,57(3):530 − 541. [LIU Juncheng,TAN Yong,SONG Xianghua,et al. Effects of through-wall leaking during excavation in water-rich sand on lateral wall deflections and surrounding environment[J]. Journal of Zhejiang University (Engineering Science),2023,57(3):530 − 541. (in Chinese with English abstract)] LIU Juncheng, TAN Yong, SONG Xianghua, et al. Effects of through-wall leaking during excavation in water-rich sand on lateral wall deflections and surrounding environment[J]. Journal of Zhejiang University (Engineering Science), 2023, 57(3): 530 − 541. (in Chinese with English abstract)
[6] WANG Jianxiu,LIU Xiaotian,LIU Jiaxing,et al. Dewatering of a 32.55 m deep foundation pit in MAMA under leakage risk conditions[J]. KSCE Journal of Civil Engineering,2018,22(8):2784 − 2801. DOI: 10.1007/s12205-017-1950-6
[7] NI J C,CHENG W C. Characterising the failure pattern of a station box of Taipei Rapid Transit System (TRTS) and its rehabilitation[J]. Tunnelling and Underground Space Technology,2012,32:260 − 272. DOI: 10.1016/j.tust.2012.06.010
[8] KORFF M,MAIR R J,VAN TOL A F,et al. Building damage and repair due to leakage in a deep excavation[J]. Proceedings of the Institution of Civil Engineers - Forensic Engineering,2011,164(4):165 − 177. DOI: 10.1680/feng.2011.164.4.165
[9] WU Congshi,GONG Liu,SHEN Weida. Monitoring and treatment during the water leakage process of a deep subway station pit[J]. Applied Mechanics and Materials,2011,94/95/96:1951 − 1956.
[10] JO Y S,CHO S H,JANG Y S. Field investigation and analysis of ground sinking development in a metropolitan city,Seoul,Korea[J]. Environmental Earth Sciences,2016,75(20):1353.
[11] LIU Juncheng,TAN Yong. Review of through-wall leaking incidents during excavation of the subway stations of Nantong metro line 1 in thick water-rich sandy strata[J]. Tunnelling and Underground Space Technology,2023,135:105056. DOI: 10.1016/j.tust.2023.105056
[12] 樊冬冬,刘祥勇,景旭成,等. 南通富水砂性地层地铁深基坑墙体渗漏原因分析[J]. 隧道建设(中英文),2020,40(增刊1):225 − 231. [FAN Dongdong,LIU Xiangyong,JING Xucheng,et al. Causes analysis on wall leaking of metro foundation pit in Nantong water-rich sandy stratum[J]. Tunnel Construction,2020,40(Sup 1):225 − 231. (in Chinese with English abstract)] FAN Dongdong, LIU Xiangyong, JING Xucheng, et al. Causes analysis on wall leaking of metro foundation pit in Nantong water-rich sandy stratum[J]. Tunnel Construction, 2020, 40(Sup 1): 225 − 231. (in Chinese with English abstract)
[13] 蒋锋平,刘国彬. 深基坑地下墙漏水引起地面沉降分析[J]. 岩土工程学报,2010,32(增刊2):574 − 577. [JIANG Fengping,LIU Guobin. Surface subsidence caused by water seeping through diaphragm wall of deep foundation pit[J]. Chinese Journal of Geotechnical Engineering,2010,32(Sup 2):574 − 577. (in Chinese with English abstract)] JIANG Fengping, LIU Guobin. Surface subsidence caused by water seeping through diaphragm wall of deep foundation pit[J]. Chinese Journal of Geotechnical Engineering, 2010, 32(Sup 2): 574 − 577. (in Chinese with English abstract)
[14] 张瑾,叶盛. 基于实测数据的基坑围护结构渗漏风险辨识[J]. 岩土工程学报,2008,30(增刊1):667 − 671. [ZHANG Jin,YE Sheng. Risk identification of retaining structure leakage in foundation pits based on measured data[J]. Chinese Journal of Geotechnical Engineering,2008,30(Sup 1):667 − 671. (in Chinese with English abstract)] ZHANG Jin, YE Sheng. Risk identification of retaining structure leakage in foundation pits based on measured data[J]. Chinese Journal of Geotechnical Engineering, 2008, 30(Sup 1): 667 − 671. (in Chinese with English abstract)
[15] TAN Yong,LU Ye. Forensic diagnosis of a leaking accident during excavation[J]. Journal of Performance of Constructed Facilities,2017,31(5):04017061.
[16] 张正,王涛,郑江,等. 某隧道工作井深基坑渗漏及堵漏处理技术[J]. 岩土工程学报,2010,32(增刊1):353 − 357. [ZHANG Zheng,WANG Tao,ZHENG Jiang,et al. Leakage and treatment technology for a foundation pit of tunnel working well[J]. Chinese Journal of Geotechnical Engineering [J]. Chinese Journal of Geotechnical Engineering,2010,32(Sup 1):353 − 357. (in Chinese with English abstract)] ZHANG Zheng, WANG Tao, ZHENG Jiang, et al. Leakage and treatment technology for a foundation pit of tunnel working well[J]. Chinese Journal of Geotechnical Engineering [J]. Chinese Journal of Geotechnical Engineering, 2010, 32(Sup 1): 353 − 357. (in Chinese with English abstract)
[17] 李义堂. 富水区深基坑止水帷幕局部渗漏处理技术[J]. 现代隧道技术,2014,51(3):188 − 192. [LI Yitang. Technology for the treatment of local water seepage of a grout curtain adopted in a deep water-rich foundation pit[J]. Modern Tunnelling Technology,2014,51(3):188 − 192. (in Chinese with English abstract)] LI Yitang. Technology for the treatment of local water seepage of a grout curtain adopted in a deep water-rich foundation pit[J]. Modern Tunnelling Technology, 2014, 51(3): 188 − 192. (in Chinese with English abstract)
[18] 郑刚,朱合华,刘新荣,等. 基坑工程与地下工程安全及环境影响控制[J]. 土木工程学报,2016,49(6):1 − 24. [ZHENG Gang,ZHU Hehua,LIU Xinrong,et al. Control of safety of deep excavations and underground engineering and its impact on surrounding environment[J]. China Civil Engineering Journal,2016,49(6):1 − 24. (in Chinese with English abstract)] ZHENG Gang, ZHU Hehua, LIU Xinrong, et al. Control of safety of deep excavations and underground engineering and its impact on surrounding environment[J]. China Civil Engineering Journal, 2016, 49(6): 1 − 24. (in Chinese with English abstract)
[19] 郑刚,戴轩,张晓双. 地下工程漏水漏砂灾害发展过程的试验研究及数值模拟[J]. 岩石力学与工程学报,2014,33(12):2458 − 2471. [ZHENG Gang,DAI Xuan,ZHANG Xiaoshuang. Experimental study and numerical simulation of leaking process of sand and water in underground engineering[J]. Chinese Journal of Rock Mechanics and Engineering,2014,33(12):2458 − 2471. (in Chinese with English abstract)] ZHENG Gang, DAI Xuan, ZHANG Xiaoshuang. Experimental study and numerical simulation of leaking process of sand and water in underground engineering[J]. Chinese Journal of Rock Mechanics and Engineering, 2014, 33(12): 2458 − 2471. (in Chinese with English abstract)
[20] 李波,喻志强,李玫,等. 渗漏对武汉地区长江一级阶地地连墙结构基坑影响的离心模型试验研究[J]. 长江科学院院报,2020,37(3):78 − 81. [LI Bo,YU Zhiqiang,LI Mei,et al. Centrifugal model test on influence of leakage on foundation pit diaphragm wall in the first-level terrace of Yangtze River in Wuhan[J]. Journal of Yangtze River Scientific Research Institute,2020,37(3):78 − 81. (in Chinese with English abstract)] DOI: 10.11988/ckyyb.20181218 LI Bo, YU Zhiqiang, LI Mei, et al. Centrifugal model test on influence of leakage on foundation pit diaphragm wall in the first-level terrace of Yangtze River in Wuhan[J]. Journal of Yangtze River Scientific Research Institute, 2020, 37(3): 78 − 81. (in Chinese with English abstract) DOI: 10.11988/ckyyb.20181218
[21] 曹卫平,席茂阳,赵呈,等. 局部破坏对内撑式排桩支护基坑影响的模型试验[J]. 水资源与水工程学报,2023,34(5):190 − 197. [CAO Weiping,XI Maoyang,ZHAO Cheng,et al. Model test of influence of local failure on internal braced row pile support[J]. Journal of Water Resources and Water Engineering,2023,34(5):190 − 197. (in Chinese with English abstract)] DOI: 10.11705/j.issn.1672-643X.2023.05.22 CAO Weiping, XI Maoyang, ZHAO Cheng, et al. Model test of influence of local failure on internal braced row pile support[J]. Journal of Water Resources and Water Engineering, 2023, 34(5): 190 − 197. (in Chinese with English abstract) DOI: 10.11705/j.issn.1672-643X.2023.05.22
[22] 胡琦,凌道盛,陈仁朋,等. 粉砂地基深基坑工程土体渗透破坏机理及其影响研究[J]. 岩土力学,2008,29(11):2967 − 2972. [HU Qi,LING Daosheng,CHEN Renpeng,et al. Research on deep foundation pit excavation due to seepage failure of soil[J]. Rock and Soil Mechanics,2008,29(11):2967 − 2972. (in Chinese with English abstract)] DOI: 10.3969/j.issn.1000-7598.2008.11.014 HU Qi, LING Daosheng, CHEN Renpeng, et al. Research on deep foundation pit excavation due to seepage failure of soil[J]. Rock and Soil Mechanics, 2008, 29(11): 2967 − 2972. (in Chinese with English abstract) DOI: 10.3969/j.issn.1000-7598.2008.11.014
[23] 郭景琢,崔肇琳,吴天凯,等. 基于坑外水位变化的基坑止水帷幕渗漏检测研究[J]. 建筑结构,2022,52(增刊2):2443 − 2450. [GUO Jingzhuo,CUI Zhaolin,WU Tiankai,et al. Refinement and application of variable particle-size methods in 3D discrete element modelling for large-scale problems[J]. Building Structure,2022,52(Sup 2):2443 − 2450. (in Chinese with English abstract)] GUO Jingzhuo, CUI Zhaolin, WU Tiankai, et al. Refinement and application of variable particle-size methods in 3D discrete element modelling for large-scale problems[J]. Building Structure, 2022, 52(Sup 2): 2443 − 2450. (in Chinese with English abstract)
[24] 戴轩,郑刚,程雪松,等. 基于DEM-CFD方法的基坑工程漏水漏砂引发地层运移规律的数值模拟[J]. 岩石力学与工程学报,2019,38(2):396 − 408. [DAI Xuan,ZHENG Gang,CHENG Xuesong,et al. Numerical simulation of ground movement induced by leakage of groundwater and sand in excavations based on the DEM-CFD method[J]. Chinese Journal of Rock Mechanics and Engineering,2019,38(2):396 − 408. (in Chinese with English abstract)] DAI Xuan, ZHENG Gang, CHENG Xuesong, et al. Numerical simulation of ground movement induced by leakage of groundwater and sand in excavations based on the DEM-CFD method[J]. Chinese Journal of Rock Mechanics and Engineering, 2019, 38(2): 396 − 408. (in Chinese with English abstract)
[25] WU Yongxia,SHEN Shuilong,LYU Haimin,et al. Analyses of leakage effect of waterproof curtain during excavation dewatering[J]. Journal of Hydrology,2020,583:124582. DOI: 10.1016/j.jhydrol.2020.124582
[26] WU Yongxia,LYU Haimin,SHEN Shuilong,et al. A three-dimensional fluid-solid coupled numerical modeling of the barrier leakage below the excavation surface due to dewatering[J]. Hydrogeology Journal,2020,28(4):1449 − 1463. DOI: 10.1007/s10040-020-02142-w
[27] 江杰,杨杉楠,胡盛斌,等. 预降水过程中止水帷幕缺陷对基坑变形的影响[J]. 广西大学学报(自然科学版),2020,45(5):996 − 1005. [JIANG Jie,YANG Shannan,HU Shengbin,et al. Influence of waterproof curtain defect on foundation pit deformation in pre-dewatering process[J]. Journal of Guangxi University (Natural Science Edition),2020,45(5):996 − 1005. (in Chinese with English abstract)] JIANG Jie, YANG Shannan, HU Shengbin, et al. Influence of waterproof curtain defect on foundation pit deformation in pre-dewatering process[J]. Journal of Guangxi University (Natural Science Edition), 2020, 45(5): 996 − 1005. (in Chinese with English abstract)
[28] 晁慧,谭勇,刘天任. 富水砂性地层中地墙渗漏诱发地层塌陷灾害的细观机制探讨[J]. 隧道建设(中英文),2023,43(7):1180 − 1189. [CHAO Hui,TAN Yong,LIU Tianren. Meso-mechanism of ground collapse induced by leaking of underground diaphragm wall in water-rich sandy strata[J]. Tunnel Construction,2023,43(7):1180 − 1189. (in Chinese with English abstract)] CHAO Hui, TAN Yong, LIU Tianren. Meso-mechanism of ground collapse induced by leaking of underground diaphragm wall in water-rich sandy strata[J]. Tunnel Construction, 2023, 43(7): 1180 − 1189. (in Chinese with English abstract)
[29] 张坤勇,张梦,孙斌,等. 考虑时空效应的软土狭长型深基坑地连墙变形计算方法[J]. 岩土力学,2023,44(8):2389 − 2399. [ZHANG Kunyong,ZHANG Meng,SUN Bin,et al. A calculation method for deformation of diaphragm wall of narrow deep foundation pit in soft soil considering spatio-temporal effect[J]. Rock and Soil Mechanics,2023,44(8):2389 − 2399. (in Chinese with English abstract)] ZHANG Kunyong, ZHANG Meng, SUN Bin, et al. A calculation method for deformation of diaphragm wall of narrow deep foundation pit in soft soil considering spatio-temporal effect[J]. Rock and Soil Mechanics, 2023, 44(8): 2389 − 2399. (in Chinese with English abstract)
[30] 程康,徐日庆,应宏伟,等. 杭州软黏土地区某30.2 m深大基坑开挖性状实测分析[J]. 岩石力学与工程学报,2021,40(4):851 − 863. [CHENG Kang,XU Riqing,YING Hongwei,et al. Performance analysis of a 30.2m deep-large excavation in Hangzhou soft clay[J]. Chinese Journal of Rock Mechanics and Engineering,2021,40(4):851 − 863. (in Chinese with English abstract)] CHENG Kang, XU Riqing, YING Hongwei, et al. Performance analysis of a 30.2m deep-large excavation in Hangzhou soft clay[J]. Chinese Journal of Rock Mechanics and Engineering, 2021, 40(4): 851 − 863. (in Chinese with English abstract)
[31] FINNO R J,CALVELLO M. Supported excavations:observational method and inverse modeling[J]. Journal of Geotechnical and Geoenvironmental Engineering,2005,131(7):826 − 836. DOI: 10.1061/(ASCE)1090-0241(2005)131:7(826)
[32] 王卫东,王浩然,徐中华. 基坑开挖数值分析中土体硬化模型参数的试验研究[J]. 岩土力学,2012,33(8):2283 − 2290. [WANG Weidong,WANG Haoran,XU Zhonghua. Experimental study of parameters of hardening soil model for numerical analysis of excavations of foundation pits[J]. Rock and Soil Mechanics,2012,33(8):2283 − 2290. (in Chinese with English abstract)] DOI: 10.3969/j.issn.1000-7598.2012.08.008 WANG Weidong, WANG Haoran, XU Zhonghua. Experimental study of parameters of hardening soil model for numerical analysis of excavations of foundation pits[J]. Rock and Soil Mechanics, 2012, 33(8): 2283 − 2290. (in Chinese with English abstract) DOI: 10.3969/j.issn.1000-7598.2012.08.008
[33] 朱宁,周洋,刘维,等. 苏州粉土地层地连墙施工对地层扰动影响研究[J]. 岩土力学,2018,39(增刊1):529 − 536. [ZHU Ning,ZHOU Yang,LIU Wei,et al. Study of silty soil behavior disturbed for installation of diaphragm wall in Suzhou[J]. Rock and Soil Mechanics,2018,39(Sup1):529 − 536. (in Chinese with English abstract )] ZHU Ning, ZHOU Yang, LIU Wei, et al. Study of silty soil behavior disturbed for installation of diaphragm wall in Suzhou[J]. Rock and Soil Mechanics, 2018, 39(Sup1): 529 − 536. (in Chinese with English abstract )