正断层对下盘影响区基坑围护桩变形的影响

doi:10.11988/ckyyb.20230504

摘要/Abstract

摘要：

为探究正断层对下盘影响区基坑围护桩变形的影响特性,以深圳市某基坑工程为案例,采用数值模拟和现场实测等综合分析方法,分析了正断层对下盘影响区围护桩变形特性及不同断层滑移量、倾角和位置对围护桩变形的影响规律,并对断层参数进行了敏感性分析和正交试验。结果表明:正断层下围护桩的变形减小,减小趋势重心下移,桩身的上部变形影响明显大于下部;桩身变形与断层滑移量、倾角成反比,与断层距基坑的距离成正比,且最大变形变化率r(ΔZ_max/Δ)随断层滑移量和倾角增大呈近似指数函数减小,随断层距基坑的距离增大呈近似对数函数增大;通过断层滑移量、倾角和位置对围护桩最大变形的敏感性分析,得到断层倾角影响最大,滑移量次之,断层位置影响最小的结论;通过64组正交试验数据拟合,得到围护桩最大变形U_hm与指标η( $η = θ π T 180 ° S$ )具有良好的线性关系,进而得到正断层对下盘影响区基坑围护桩最大变形的预测模型和该项目预测公式。研究结果可为正断层区域类似地质条件下的基坑工程变形控制提供参考。

关键词: 正断层, 下盘影响区, 基坑围护桩变形, 数值模拟, 现场实测, 敏感性分析, 预测模型

Abstract:

To investigate the deformation characteristics of retaining piles in the footwall influenced by normal faults, a case study of a foundation pit project in Shenzhen City was conducted using a comprehensive approach that included numerical simulations and field measurements. The study examined how different fault slip amounts, dip angles, and positions affect the deformation of retaining piles in the footwall’s influence zone. Sensitivity analysis and orthogonal experiments were carried out to assess the impact of these fault parameters. Results revealed that deformation of the retaining piles decreased under the normal fault, with the center of gravity shifting downward. The upper sections of the piles experienced more significant deformation compared to the lower sections. Deformation was inversely proportional to both the fault slip amount and dip angle, and directly proportional to the distance from the fault to the foundation pit. Specifically, the maximum deformation rate, r(ΔZ_max/Δ), decreased exponentially with increasing fault slip amount and dip angle, but increased logarithmically with increasing distance from the fault. Sensitivity analysis showed that dip angle had the most significant impact on the maximum deformation of the retaining piles, followed by slip amount, with the fault position having the least influence. By fitting data from 64 orthogonal experiments, a strong linear relationship was established between the maximum deformation U_hm and the index η( $θ π T 180 ° S$ ).Consequently,a predictive model for the maximum deformation of retaining piles in the footwall’s influence zone was developed, along with a corresponding predictive equation for this project. These findings offer valuable insights for deformation control in foundation pit projects located in normal fault areas with similar geological conditions.

Key words: normal fault, footwall influence zone, deformation of foundation pit retaining pile, numerical simulation, field measurement, sensitivity analysis, prediction model

中图分类号:

TU94地下建筑施工、施工机械与设备

牛云岗, 麻凤海, 王琼亿. 正断层对下盘影响区基坑围护桩变形的影响[J]. 院报, 2024, 41(9): 130-137.

NIU Yun-gang, MA Feng-hai, WANG Qiong-yi. Deformation of Foundation Pit Retaining Piles in Footwall Zone Influenced by Normal Fault[J]. Journal of Yangtze River Scientific Research Institute, 2024, 41(9): 130-137.

图/表 15

图1 基坑-正断层横剖面示意图

Fig.1 Cross-section of foundation pit and normal fault

表1 支护结构截面尺寸和物理力学性能参数

Table 1 Sectional dimensions and physical-mechanicalparameters of support structure

名称	材料	截面尺寸	弹性模量 E/GPa	泊松比ν
咬合桩 (等效连续墙)	C30	厚度880 mm	30	0.2
立柱	C30	Φ1 200 mm	30	0.2
冠梁	C30	1 000 mm×1 200 mm	30	0.2
支撑梁	C30	1 000 mm×1 200 mm	30	0.2
连梁	C30	1 000 mm×1 200 mm	30	0.2

表2 土层计算参数

Table 2 Computation parameters of soil strata

地层	层厚/m	重度γ/ (kN·m^-3)	割线刚度 /MPa	切线刚度 /MPa	卸载刚度 /MPa	泊松比ν	黏聚力c/ kPa	内摩擦角φ/ (°)	渗透系数K/ (m·d^-1)
①素填土	4.40	19.0	2.0	2.0	6.0	0.35	14	15	5.0
②黏土	3.05	18.5	2.8	2.8	8.4	0.33	25	18	0.1
③角砾	0.80	19.5	6.0	6.0	18.0	0.28	0	36	25.0
④砂质黏性土	4.60	21.0	8.0	8.0	24.0	0.26	25	22	5.0
⑤全风化混合岩	6.95	20.0	16.0	16.0	48.0	0.24	23	28	0.1
⑥强风化混合岩	6.90	20.5	25.0	25.0	75.0	0.23	20	32	0.5
⑦中风化混合岩	未揭穿	21.0	70.0	70.0	210.0	0.22	200	50	0.5

图2 三维有限元计算模型

Fig.2 Three-dimensional numerical calculation model

表3 接触面计算参数

Table 3 Computation parameters for contact surface

滑移面	法向刚度K_n/ ( kN·m^-1)	切向刚度K_s/ ( kN·m^-1)	内摩擦角 φ/(°)	黏聚力 c/kPa
土-土界面单元	5.6×10⁴	5.6×10³	13	10
岩-岩界面单元	3.2×10⁶	3.2×10⁵	32	22

图3 基坑开挖完成时和正断层粘结滑移下围护桩水平位移云图

Fig.3 Contours of horizontal displacement of retaining piles at excavation completion and normal fault’s bond slip

图4 围护桩变形数值计算结果对比

Fig.4 Numerical results of retaining wall deformation

图5 实测点平面布置

Fig.5 Plane layout of measurement points

图6 围护桩变形监测对比

Fig.6 Comparison of monitoring result of retaining pile deformation

图7 不同滑移量下围护桩变形对比

Fig.7 Deformations of retaining piles under different sliding amounts

图8 不同倾角下围护桩变形对比

Fig.8 Deformations of retaining piles under different inclination angles

图9 不同位置下围护桩变形对比

Fig.9 Deformations of retaining piles at different locations

表4 敏感因子汇总

Table 4 List of sensitive factors

指标	断层滑移量T	断层倾角θ	断层位置S
围护桩最大变形敏感因子P	0.203	0.400	0.185

表5 因素水平

Table 5 Factor levels

水平	断层滑移量T/mm	断层倾角θ/(°)	断层位置S/m
1	3	45	20
2	9	62	25
3	18	72	30
4	27	82	35

图10 正断层下围护桩最大变形预测曲线

Fig.10 Predicted maximum deformations of retaining piles in the footwall zone of normal fault

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