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1 GLOBAL GEOLOGY Vol. 35 No. 2 Jun Processing Modflow Processing Modflow 80 m ~ cm 80 m ~ mm Processing Modflow TU992 A doi /j. issn Application of Processing Modflow in drainage of foundation pit SUN Huai-jun LI Lian-ying LIU Cheng-lei Tianjin Institute of Geotechnical Investigation & Surveying Tianjin China Abstract Taking a foundation pit in Tianjin as the research subject the authors established a three dimensional coupling model between groundwater flow and land subsidence by the Processing Modflow numerical simulation software. The real time change of the underground water level and land subsidence around the pit was simulated when the foundation pit dewatered and drained in case of the construction of supporting and water proof curtain the value of underground water reduction caused by drainage of foundation pit is about between cm and cm around foundation pit within 80 m area. Within the 80 m area the land subsidence is between mm and mm. The results are in good agreement with the latter monitoring data which can reflect the influence of the precipitation process to the surrounding environment. Key words foundation pit drainage coupling model Processing Modflow Tianjin #

2 m mm m Processing Modflow m 53 S1 ~ S m 64 J1 ~ J m 6 B1 ~ B6 24 G1 ~ G m GY1 ~ GY m ~ m ~ m Fig. 1 1 Sketch map of floor plan for dewatering well

3 2 Processing Modflow 551 Table 1 1 Vertical stratification for foundation pit section with waterproof curtain / m / m ± / m /m m 220 m ± m m 2 Table 2 2 Vertical stratification for foundation pit section with model / m / m S m J m m m

世 552 界地质第 35 卷基坑中心单元密的原则对研究区进行三维剖分将整个计算区域在平面上剖分成 89 99 的矩形网 3 本次模型数值模拟设置单井涌水量 6.

4 世 552 界地质第 35 卷基坑中心单元密的原则对研究区进行三维剖分将整个计算区域在平面上剖分成的矩形网 3 本次模型数值模拟设置单井涌水量 m / d 连续抽排 20 d 考虑止水帷幕底部越流补给格单元垂向上依据上述分成 17 层每层的网格单元总数为个共计个计算单元格基坑内外有水力联系渗流模式抽取基坑内水会降低坑内水位地下水会产生随动效应下部含水层图 2 计算区域上下边界为隔水边界四周水平侧向外边界取为定水头边界外边界的初始水位通过越流补给补充上部水位由于基坑内外存在水头差同时引起基坑外地下水绕过止水帷幕底部补由各层含水层的初始流场获得内边界条件根据现场实际情况确定给坑内在基坑外部由远及近随动效应增加图2 Fig. 2 3 模型网格划分及监测点示意图 Schematic model of mesh and monitoring points 三维地下水渗流地面沉降耦合模型根据水文地质模型利用地下水三维渗流与地面沉降耦合模型计算软件 Processing Modflow 经过 6 7 概念模型数学模型数值模型等几个阶段建立了符合研究区域的三维地下水渗流地面沉降数值模型预测在基坑降水的条件下的地面沉降量及地下水位变化 3. 1 ( 地下水运动数学模型 ) ( ) ( ) h + h + h W = S h 1 k k k s x x x y y y z z z t H x y t t = t0 = H0 x y z t0 2 x y z Ω H x y z t Γ1 = H1 x y z t x y z Γ1 3

5 2 Processing Modflow 553 H x y z t = z k H xx ( x ) + kyy H ( y ) + kzz H ( z ) - H z k zz + q w + q w Γ3 = μ h t x y z Γ 3 4 x y z Δb m L k x k y k z Δb * m Δh m b 0 LT - 1 H m n S fe L W T - 1 S s S fv S ske L - 1 S s = y W 1-2μ t E 1 - μ 1 /m S skv 1 /m n w T Ω H 0 x y z t 0 G x y z m H 1 x y z t MPa v C c p cos n x cos MPa e 0 ρ w n y cos n z kg /m 3 μ S fe S fv q w m /d Γ 1 Γ 3 Ⅰ 3. 2 ± m m - Δb = - Δh 1 - n + n w S ske b 0 = - ΔhS fe m m obs1 ~ obs13 Δb * = - Δh 1 - n + n w S skv b 0 = - ΔhS fv 8 obs14 ~ obs24 S ske S skv = ρ w g [ ] 3 1-2v 2G 1 + v = C cρ w g p 1 + e d ~ 5 d Δb = - ΔhS ske b 0 = - ΔhS fe 5 9 Δb * = - ΔhS skv b 0 = - ΔhS fv 6

6 obs25 ~ obs35 obs36 ~ obs Fig. 3 3 Schematic drawing of actual monitoring points obs12 obs23 obs34 obs45 G2 80 m 60 m 40 m 20 m 2 m Fig. 4 obs37 Fitting for obs37 drawdown obs37

7 2 Processing Modflow 555 Table 3 3 Parameters for foundation pit section and model s vertical stratification and inversion cm s - 1 cm s E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E Fig. 5 5 obs 37 Fitting for obs37 ground subsidence mm obs23 6b 7b obs23 60 m cm mm obs34 6c 7c obs34 40 m cm mm obs45 6d 7d obs45 20 m cm obs 12 6a mm 7a obs12 80 m G2 2 m cm cm mm

8 a obs12 b obs23 c obs34 d obs45. 6 Fig. 6 Fitting for drawdown 80 m cm 60 m ~ mm 1 cm 80 m mm 60 m ~ mm cm mm cm mm cm mm 1 G cm mm

9 2 Processing Modflow 557 a obs12 b obs23 c obs34 d obs45. Fig. 7 7 Fitting for ground subsidence Fig Contour map of prediction changes for drawdown Fig. 9 Counter map of prediction cnmulative changes for ground subsidence

10 FENG Xiao-la XIONG Zong-hai MO Yun et al. Numerical simulation and analysis of surrounding environ- ment deformationinfluenced by excavation of foundation 3 pits under complex conditions J. Chinese Journal of Geotechnical Engineering Suppl Chiang W H H Kinzelbach W. 3D groundwater modeling 4 with PMWIN a simulation system for modeling groundwater flow and pollution M. Berlin Springer J ZHANG Yun XUE Yu-qun. Present sitution and prospect on the mathematical model of land subsidence due to 1. pumping. The Chinese Journal of Geological Hazard and J. Control LUO Zu-jiang LI Lang YAO Tian-qiang et al. Coupling model of three dimensional seepage and land-subsid- J ence for dewatering of deep foundation pit in loose confined aquifers J. Chinese Journal of Geotechnical Engi- PING Yang BAI Shi-wei XU Yan-ping. Numerical simulation of seepage and stress coupling analysis in deep neering # J LUO Zu-jiang ZHANG Yue-ping LIU Jin-bao et al. Three- dimensional seepage numerrical simulation of deep foundation pit dewatering in complicated quaternary loose sediments with great thickness a case study of dewatering reconstructed foundation pit at Dongjiadu Subway of the 4th line in Shanghai J. Chinese Journal of Rock Mechanics and Engineering Suppl ground Space and Engineering Suppl. 2 J CHEN Xing-xian LUO Zu-jiang AN Xiao-yu et al. Coupling model of groundwater three dimensional variable parametric non-steady seepage and land-subsidence J. Journal of Jilin University Earth Science Edition 2013 foundation pit J. Rock and Soil Mechanics J LI Wen-guang HU Chang-ming. Surface subsidence caused by dewatering in deep foundation pit J. Chinese Journal of Underground Space and Engineering J YE Wei-min WAN Min CHEN Bao et al. Influence of dewatering of confined aquifers on land subsidence during deep excavation J. Chinese Journal of Under FLAC 3D J MA Hong JI Cong YANG Rui-gang et al. Numerical simulation analysis of foundation pit support using FLAC D J. Global Geology J.

增刊谢小林, 等. 上海中心裙房深大基坑逆作开挖设计及实践 745 类型, 水位埋深一般为地表下.0~.7 m 场地地表以下 27 m 处分布 7 层砂性土, 为第一承压含水层 ; 9 层砂性土

增刊谢小林, 等. 上海中心裙房深大基坑逆作开挖设计及实践 745 类型, 水位埋深一般为地表下.0~.7 m 场地地表以下 27 m 处分布 7 层砂性土, 为第一承压含水层 ; 9 层砂性土第 34 卷增刊岩土工程学报 Vol.34 Supp. 202 年. 月 Chinese Journal of Geotechnical Engineering Nov. 202 上海中心裙房深大基坑逆作开挖设计及实践谢小林 2 2, 翟杰群, 张羽, 杨科, 郭晓航, 贾坚 (. 同济大学建筑设计研究院 (