作者中心
专家审稿
编委审稿
主编审稿
EFFECT OF CROSS WALL HEIGHT ON ENCLOSURE WALL DEFLECTION INCURRED BY PUMPING TEST BEFORE BULK EXCAVATION
-
摘要: 基坑挖前抽水可诱发明显围挡变形，而常用的墙顶支撑方案尚不能很好地防控围挡深部位置变形。近期，有学者针对软土地区基坑施工常用的“坑内布设隔墙的分区段施做方法”，提出了“考虑隔墙支护效应”及“优化布置隔墙”的变形防控理念，实现了基坑挖前抽水引发变形的有效控制。为进一步优化坑内隔墙的布置，本文开展了隔墙高度对挖前抽水引发变形的影响研究。针对某具体基坑工程，通过一系列数值分析，探究了在不同抽水深度、隔墙高度条件下挖前抽水引发的基坑围挡变形特性，并基此提出了隔墙在深度方向的优化布置方案。研究表明，隔墙在深度方向的布置范围对其变形控制效果有很大影响，具体地，在降水深度范围内布设隔墙可显著减小抽水引发的围挡侧移，而降水深度以下的隔墙布设对围护结构侧移的控制作用十分有限。为兼顾经济性与变形控制效果，建议将隔墙顶面设置在降水深度(Hd)以上0.33~0.67Hd位置处，隔墙底面设置在Hd处；但当坑外存在对变形敏感的深埋结构时，可将隔墙底面进一步向下延伸1/3Hf(Hf为降水深度至围护结构底面距离)以达到控制深埋结构变形的目的。Abstract: Dewatering before bulk excavation is able to cause centimeter-level wall deflection, while the commonly-used inner strut system cannot effectively limit the wall deflection at deep location. Recently, aiming at the inner cross-wall system frequently used to achieve sectionalized construction in soft soil area, some scholars proposed a deformation-control idea of making use of cross wall and optimizing its layout, which effectively restricts the dewatering-induced deformation. This paper aims to further optimize the arrangement of the cross wall to ensure the deformation control effect under the most economical conditions. It investigates the influence of cross wall height on the enclosure wall deflection incurred by dewatering before bulk excavation. Based on an actual foundation pit, a series of numerical simulations are conducted to explore the deformation characteristics of enclosure wall incurred by dewatering before bulk excavation under different pumping depths and cross wall height. On this basis, this paper proposes the optimized layout of cross wall in depth direction. Results show that the layout of cross wall in depth direction has a great influence on its deformation control effect. Specifically, the installation of cross wall within the pumping depth can significantly reduce the retaining wall deflection triggered by pumping, while the installation of cross wall below the pumping depth has a very limited effect on the control of retaining wall deformation. In order to take into account both the economy and deformation control effect, this paper recommends to set the cross wall top at 0.33-0.67Hd above the pumping depth(Hd) and set the cross wall bottom at Hd. When there are deeply-buried structures outside the pit which are sensitive to deformation, it should be better to extend the cross wall bottom downward by 1/3Hf to achieve the deformation control of deeply buried structures, where Hf is the distance between the pumping depth location to the retaining wall bottom.
-
Key words:
- Soft soil /
- Dewatering /
- Cross wall /
- Numerical analysis /
- Wall deflection
-
图 1 曾超峰等(2021a, 2021b)提出的隔墙间距与内挑长度优化布置方案
a. 平面图；b. A-A剖面图
Figure 1. Optimized layout of cross wall proposed by Zeng et al.(2021a,2021b)
图 4 测斜孔C1和C3处侧移计算与实测值对比
Figure 4. Comparison between computed and observed wall deflection at C1 and C3
图 5 基坑围挡-坑内隔墙的模型布置
Figure 5. Layout of enclosure wall and inner cross wall in the model
图 7 不同hc1条件下基坑围挡顶部变形水平分布
Figure 7. Distribution of enclosure wall deflection on wall crown along the horizontal direction under different hc1
a. Hd=11 m; b. Hd=21.5 m
图 8 不同hc1条件下隔墙处基坑围挡变形竖向分布
Figure 8. Distribution of enclosure wall deformation along depth under different hc1
a. Hd=11 m; b. Hd=21.5 m
图 11 不同hc2条件下基坑围挡顶部变形的水平分布
Figure 11. Distribution of enclosure wall deflection on wall crown along horizontal direction under different hc2
a. hc1/Hd=0; b. hc1/Hd=1
图 12 不同hc2条件下横隔墙位置处基坑围挡变形的竖向分布
Figure 12. Distribution of enclosure wall deformation along depth under different hc2
a. Hd=11 m; b. Hd=21.5 m
表 1 各土层修正剑桥模型计算参数
Table 1. Calculation parameters of each soil used in the Modified Cam-Clay model
土的类型 层底埋深/m λ κ M γ/kN·m-3 e kv/m·d-1 kh/m·d-1 K0 粉质黏土 5.5 0.0553 0.0065 0.979 19.35 0.811 0.1 0.1 0.49 黏质粉土 11.0 0.0312 0.0036 1.192 19.30 0.792 0.5 0.5 0.43 粉质黏土 19.0 0.0445 0.0052 0.979 20.10 0.696 1×10-4 5×10-4 0.50 砂质粉土 24.0 0.0293 0.0034 1.202 20.15 0.640 1 1 0.42 黏土 27.0 0.0397 0.0046 0.800 19.75 0.764 1×10-5 5×10-5 0.55 砂质粉土 33.0 0.0283 0.0033 1.202 20.65 0.583 0.7 1 0.35 粉质黏土 37.0 0.0320 0.0037 0.900 20.50 0.611 3×10-4 5×10-4 0.39 粉、细砂 42.0 0.0191 0.0022 1.382 20.50 0.585 1.5 2.5 0.30 粉质黏土 50.0 0.0305 0.0035 0.900 19.30 0.864 2×10-4 5×10-4 0.39 
下载: 导出CSV
表 2 模型计算工况参数取值表
Table 2. Parameter values used in different calculation conditions
Hd/m hc1/Hd(hc2/Hf) hc1/m hc2/m 11 0 0 0 1/3 4 7 2/3 8 14 1 11 22 16 0 0 0 1/3 5 6 2/3 10 12 1 16 17 19 0 0 0 1/3 6 5 2/3 12 10 1 19 14 21.5 0 0 0 1/3 7 4 2/3 14 8 1 22 11
下载: 导出CSV
-
He S H,Xia T D,Li L X,et al. 2019. Influence of groundwater seepage on deformation of foundation pits with suspended impervious curtains[J]. Journal of Zhejiang University(Engineering Science),53 (4): 713-723. Hu R G, Liu H J, Wang Z Y, et al. 2020. Deformation analysis of supporting structure for soil-rock combination foundation pit with adjacent buildings in coastal area[J]. Journal of Engineering Geology, 28 (6): 1368-1377. Li M G, Demeijer O, Chen J J. 2020. Effectiveness of servo struts in controlling excavation-induced wall deflection and ground settlement[J]. Acta Geotechnica, 15 : 2575-2590. doi: 10.1007/s11440-020-00941-9 Li M G, Zhang Z J, Chen J J, et al. 2017. Zoned and staged construction of an underground complex in shanghai soft clay[J]. Tunnelling and Underground Space Technology, 67 : 187-200. doi: 10.1016/j.tust.2017.04.016 Li M K. 2019. Effect of cross wall layout on foundation deformation caused by dewatering before soil excavation[D]. Xiangtan: Hunan University of Science and Technology. Li M, Xu Y, Zhang B. 2020. Research on lateral stiffness of strutted retaining structure for deep excavation[J]. Journal of Engineering Geology, 28 (5): 1116-1122. Liang F Y, Jia Y J, Ding Y J, et al. 2017. Experimental study on parameters of HSS model for soft soils in Shanghai[J]. Chinese Journal of Geotechnical Engineering, 39 (2): 269-278. Ou C Y, Hsieh P G, Lin Y L. 2011. Performance of excavations with cross walls[J]. Journal of Geotechnical and Geoenvironmental Engineering, 137 (1): 94-104. doi: 10.1061/(ASCE)GT.1943-5606.0000402 Pujades E, Vázquez-Suñé E, Carrera J, et al. 2014. Deep enclosures versus pumping to reduce settlements during shaft excavations[J]. Engineering Geology, 169 : 100-111. doi: 10.1016/j.enggeo.2013.11.017 Qin S W, Miao Q, Zhang L S, et al. 2020. Finite element analysis on influence of excavation and support removal of foundation pit to surrounding environment[J]. Journal of Engineering Geology, 28 (5): 1106-1115. Shi Y Z, Hua J B, Lian Y X, et al. 2018. Safety evaluation and protection measures to adjacent pipelines during deep excavation for metro construction[J]. Journal of Engineering Geology, 26 (4): 1043-1053. Tan Y, Li X, Kang Z, et al. 2015. Zoned excavation of an oversized pit close to an existing metro line in stiff clay: Case study[J]. Journal of Performance of Constructed Facilities, 29 (6): 1-19. Tan Y, Lu Y, Wang D. 2018. Deep excavation of the gate of the orient in suzhou stiff clay: Composite earth-retaining systems and dewatering plans[J]. Journal of Geotechnical and Geoenvironmental Engineering, 144(3): 05017009. doi: 10.1061/(ASCE)GT.1943-5606.0001837 Tan Y, Wei B, Lu Y, et al. 2019. Is basal reinforcement essential for long and narrow subway excavation bottoming out in shanghai soft clay[J]. Journal of Geotechnical and Geoenvironmental Engineering, 145(5): 05019002. doi: 10.1061/(ASCE)GT.1943-5606.0002028 Wang J X, Liu X T, Liu S L, et al. 2019. Physical model test of transparent soil on coupling effect of cut-off wall and pumping wells during foundation pit dewatering[J]. Acta Geotechnica, 14 : 141-162. doi: 10.1007/s11440-018-0649-2 Wu Y X, Lyu H M, Han J, et al. 2019. Dewatering-induced building settlement around a deep excavation in soft deposit in tianjin, China[J]. Journal of Geotechnical and Geoenvironmental Engineering, 145(5): 05019003. doi: 10.1061/(ASCE)GT.1943-5606.0002045 Xu C J, Zeng Y T, Tian W, et al. 2021. Analytical analysis of influence of dewatering on adjacent pipelines based on Pasternak foundation[J]. Journal of Shanghai Jiao Tong University, 55 (6): 652-662. Xu Y S, Yan X X, Shen S L, et al. 2019. Experimental investigation on the blocking of groundwater seepage from a waterproof curtain during pumped dewatering in an excavation[J]. Hydrogeology Journal, 27 : 2659-2672. doi: 10.1007/s10040-019-01992-3 Zeng C F, Liao H, Li M K, et al. 2021a. Effect of buttress wall length on retaining wall deflection induced by dewatering[J]. Journal of Zhejiang University(Engineering Science), 55 (12): 2252-2259. Zeng C F, Wang S, Song W W, et al. 2021b. Control effect of cross wall on metro foundation pit deformation induced by pre-excavation dewatering in soft soil[J]. Chinese Journal of Rock Mechanics and Engineering, 40 (6): 1277-1286. Zeng C F, Zheng G, Xue X L. 2017. Wall deflection induced by pre-excavation dewatering in large-scale excavations[J]. Chinese Journal of Geotechnical Engineering, 39 (6): 1012-1021. Zeng C F, Zheng G, Zhou X F, et al. 2019. Behaviours of wall and soil during pre-excavation dewatering under different foundation pit widths[J]. Computers and Geotechnics, 115: 103169. doi: 10.1016/j.compgeo.2019.103169 Zheng G, Zeng C F. 2013. Lateral displacement of diaphragm wall by dewatering of phreatic water before excavation[J]. Chinese Journal of Geotechnical Engineering, 35 (12): 2153-2163. Zheng G, Zhao Y B, Cheng X S, et al. 2019. Strategy and analysis of the settlement and deformation caused by dewatering under complicated geological condition[J]. China Civil Engineering Journal, 52 (S1): 135-142. Zhou Y, Hu Y L. 2021. Calculation for displacement and internal force of pile anchor retaining structure based on improved increment method[J]. Journal of Engineering Geology, 29 (1): 229-236. 何绍衡, 夏唐代, 李连祥, 等. 2019. 地下水渗流对悬挂式止水帷幕基坑变形影响[J]. 浙江大学学报(工学版), 53 (4): 713-723. https://www.cnki.com.cn/Article/CJFDTOTAL-ZDZC201904012.htm 胡瑞庚, 刘红军, 王兆耀, 等. 2020. 邻近建筑物的滨海土岩组合基坑支护结构变形分析[J]. 工程地质学报, 28 (6): 1368-1377. doi: 10.13544/j.cnki.jeg.2019-545 李冕, 徐阳, 张搏. 2020. 深基坑竖向支承系统的侧向刚度研究[J]. 工程地质学报, 28 (5): 1116-1122. doi: 10.13544/j.cnki.jeg.2020-430 李淼坤. 2019. 横隔墙布置方式对开挖前降水引发基坑变形影响规律研究[D]. 湘潭: 湖南科技大学. 梁发云, 贾亚杰, 丁钰津, 等. 2017. 上海地区软土hss模型参数的试验研究[J]. 岩土工程学报, 39 (2): 269-278. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201702012.htm 秦胜伍, 苗强, 张领帅, 等. 2020. 基坑开挖与支撑拆除对周围环境影响的研究[J]. 工程地质学报, 28 (5): 1106-1115. doi: 10.13544/j.cnki.jeg.2020-275 施有志, 华建兵, 连宇新, 等. 2018. 地铁深基坑施工扰动下邻近管线安全评价及保护措施[J]. 工程地质学报, 26 (4): 1043-1053. doi: 10.13544/j.cnki.jeg.2017-295 徐长节, 曾怡婷, 田威, 等. 2021. Pasternak地基降水对邻近管线影响的解析研究[J]. 上海交通大学学报, 55 (6): 652-662. https://www.cnki.com.cn/Article/CJFDTOTAL-SHJT202106004.htm 曾超峰, 廖欢, 李淼坤, 等. 2021a. 内隔墙长度对抽水引发基坑围挡侧移的影响[J]. 浙江大学学报(工学版), 55 (12): 2252-2259. https://www.cnki.com.cn/Article/CJFDTOTAL-ZDZC202112004.htm 曾超峰, 王硕, 宋伟炜, 等. 2021b. 内隔墙对开挖前抽水引发软土区地铁深基坑变形的控制效果[J]. 岩石力学与工程学报, 40 (6): 1277-1286. https://www.cnki.com.cn/Article/CJFDTOTAL-YSLX202106018.htm 曾超峰, 郑刚, 薛秀丽. 2017. 大面积基坑开挖前预降水对支护墙变形的影响研究[J]. 岩土工程学报, 39 (6): 1012-1021. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201706008.htm 郑刚, 曾超峰. 2013. 基坑开挖前潜水降水引起的地下连续墙侧移研究[J]. 岩土工程学报, 35 (12): 2153-2163. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201312002.htm 郑刚, 赵悦镔, 程雪松, 等. 2019. 复杂地层中基坑降水引发的水位及沉降分析与控制对策[J]. 土木工程学报, 52 (S1): 135-142. https://www.cnki.com.cn/Article/CJFDTOTAL-TMGC2019S1019.htm 周勇, 胡玉丽. 2021. 基于改进增量法的桩锚支护结构位移与内力计算[J]. 工程地质学报, 29 (1): 229-236. doi: 10.13544/j.cnki.jeg.2020-039 -
点击查看大图
图(14) / 表(2)
计量
- 文章访问数: 49
- HTML全文浏览量: 10
- PDF下载量: 12
- 被引次数: 0
