地铁变频荷载循环作用下饱和软黏土累积塑性变形

doi:10.16183/j.cnki.jsjtu.2021.036

摘要/Abstract

摘要：

地铁在地铁站附近的加减速运动会对地基土产生一定的影响.土体经过倾斜削样后使用动三轴进行不排水动力测试以研究地铁进出站作用下进出站距离、加速度、动应力幅值及固结围压对饱和软黏土累积塑性变形的影响.结果表明:进出站变频荷载循环作用下软黏土累积塑性应变曲线可大致划分为爆发增长-较快增长-逐渐稳定3个阶段.距地铁站越近、动应力幅值越大、固结围压越小,土体进入逐渐稳定阶段所需的进出站次数越少,土体竖向变形越大,剪切变形越小.进出站加速度值越大,土体竖向变形越小、剪切变形越大.对于实际工程而言,地铁运营初期,进站区间土体的沉降变形、出站区间土体水平位移、较大加速度工况下的水平位移、较小加速度工况下的沉降、高动应力幅值的工况及低固结应力的土体区域是工程地质灾害防治的重点.

关键词: 地下工程, 变频循环荷载, 加速度, 累积变形, 不排水动三轴试验, 软黏土

Abstract:

The acceleration and deceleration movement of the metro near the metro station have a certain impact on the foundation soil. After the soil has been sloped and sampled, a dynamic three-axis undrained dynamic test is conducted to study the influence of the distance of the metro station, acceleration, dynamic stress amplitude, and consolidation confining pressure on the cumulative plastic deformation of saturated soft clay. The results show that the cumulative plastic strain curve of soft clay at variable frequency cyclic loading in and out of the station can be roughly divided into three stages: explosive growth, rapid growth, and gradual stability. The increase in the distance from the metro station, the increase in the amplitude of the dynamic stress, and the decrease in the consolidation confining pressure can reduce the number of entry and exit times required for the soil to enter the gradual stabilization phase, increase the vertical deformation of the soil, and reduce the shear deformation. As the acceleration value in and out of the station increases, the vertical deformation of the soil decreases but the shear deformation increases. For the actual project, the initial stage of metro operation, the settlement deformation of the soil in the inbound section, the horizontal displacement of the soil in the outbound section, the horizontal displacement under the larger acceleration condition, the settlement under the smaller acceleration condition, the high dynamic stress amplitude, and the soil area with a low consolidation stress are the focus of engineering geological disaster prevention.

Key words: underground engineering, variable frequency cyclic load, acceleration, cumulative deformation, undrained dynamic triaxial test, soft clay

中图分类号:

TU473

李泽垚, 周洁, 田万君, 裴万胜. 地铁变频荷载循环作用下饱和软黏土累积塑性变形[J]. 上海交通大学学报, 2022, 56(4): 454-463.

LI Zeyao, ZHOU Jie, TIAN Wanjun, PEI Wansheng. Accumulative Plastic Deformation of Saturated Soft Clay Under Variable Frequency Cyclic Loading for Subway[J]. Journal of Shanghai Jiao Tong University, 2022, 56(4): 454-463.

图/表 14

图1

图2

表1

图3

图4

表2

软黏土累积变形试验方案

试样编号	固结围压/kPa	进出站加速度/(m·s^-2)	列车竖向动应力/kPa	进出站距离/m	试验加载动应力/kPa	削样角度/(°)
A1	125	-0.50	30±15	+50	30.08±15.04	2.91
A2	125	-0.50	30±15	+150	30.08±15.04	2.91
A3	125	-0.50	30±15	+250	30.08±15.04	2.91
A4	125	-0.55	30±15	+50	30.09±15.05	3.20
A5	125	-0.55	30±15	+150	30.09±15.05	3.20
A6	125	-0.55	30±15	+250	30.09±15.05	3.20
A7	125	-0.60	30±15	+50	30.11±15.06	3.49
A8	125	-0.60	30±15	+150	30.11±15.06	3.49
A9	125	-0.60	30±15	+250	30.11±15.06	3.49
A10	100	-0.55	30±10	+50	30.09±10.03	3.20
A11	100	-0.55	30±10	+150	30.09±10.03	3.20
A12	100	-0.55	30±10	+250	30.09±10.03	3.20
A13	150	-0.55	30±20	+50	30.09±20.06	3.20
A14	150	-0.55	30±20	+150	30.09±20.06	3.20
A15	150	-0.55	30±20	+250	30.09±20.06	3.20
A16	100	-0.55	30±15	+50	30.09±15.05	3.20
A17	100	-0.55	30±15	+150	30.09±15.05	3.20
A18	100	-0.55	30±15	+250	30.09±15.05	3.20
A19	150	-0.55	30±15	+50	30.09±15.05	3.20
A20	150	-0.55	30±15	+150	30.09±15.05	3.20
A21	150	-0.55	30±15	+250	30.09±15.05	3.20
B1	125	+0.85	30±15	+50	30.22±15.11	4.92
B2	125	+0.85	30±15	+150	30.22±15.11	4.92
B3	125	+0.85	30±15	+250	30.22±15.11	4.92
B4	125	+0.90	30±15	+50	30.25±15.13	5.20
B5	125	+0.90	30±15	+150	30.25±15.13	5.20
B6	125	+0.90	30±15	+250	30.25±15.13	5.20
B7	125	+0.95	30±15	+50	30.28±15.14	5.49
B8	125	+0.95	30±15	+150	30.28±15.14	5.49
B9	125	+0.95	30±15	+250	30.28±15.14	5.49
B10	125	+1.00	30±15	+50	30.31±15.15	5.77
B11	125	+1.00	30±15	+150	30.31±15.15	5.77
B12	125	+1.00	30±15	+250	30.31±15.15	5.77
B13	100	+0.90	30±10	+50	30.25±10.08	5.20
B14	100	+0.90	30±10	+150	30.25±10.08	5.20
B15	100	+0.90	30±10	+250	30.25±10.08	5.20
B16	150	+0.90	30±20	+50	30.25±20.17	5.20
B17	150	+0.90	30±20	+150	30.25±20.17	5.20
B18	150	+0.90	30±20	+250	30.25±20.17	5.20
B19	100	+0.90	30±15	+50	30.25±15.13	5.20
B20	100	+0.90	30±15	+150	30.25±15.13	5.20
B21	100	+0.90	30±15	+250	30.25±15.13	5.20
B22	150	+0.90	30±15	+50	30.25±15.13	5.20
B23	150	+0.90	30±15	+150	30.25±15.13	5.20
B24	150	+0.90	30±15	+250	30.25±15.13	5.20

表2

图5

图6

图7

图8

图9

图10

图11

表3

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重度/ (kN·m^-3)	含水率/ %	孔隙比	压缩系数/ MPa^-1	内摩擦角/(°)	黏聚力/ kPa	渗透系数×10⁶/(m·s^-1)		液限/%	塑限/%	动泊松比	波速/(m·s^-1)
重度/ (kN·m^-3)	含水率/ %	孔隙比	压缩系数/ MPa^-1	内摩擦角/(°)	黏聚力/ kPa	水平	竖直	液限/%	塑限/%	动泊松比	压缩		剪切
18.4	35.9	1.04	0.63	7.6	14.0	5.09	3.61	36.1	21.6	0.439	360		120

试样编号	竖向应变				切应变
试样编号	a	b	c	相关系数	a	b	c	相关系数
A2	1.729	0.462	0.441	0.996	17.739	3.252	0.491	0.990
A4	0.964	0.424	0.432	0.996	5.979	2.628	0.432	0.996
A5	2.026	0.467	0.452	0.990	12.566	2.897	0.452	0.996
A6	3.497	0.492	0.502	0.997	21.688	3.053	0.502	0.992
A8	2.606	0.478	0.491	0.997	9.848	2.631	0.441	0.988
A11	2.659	0.488	0.434	0.994	16.489	3.025	0.434	0.996
A14	1.551	0.436	0.472	0.992	10.024	2.754	0.496	0.989
A17	1.922	0.451	0.452	0.994	11.922	2.799	0.452	0.990
A20	2.543	0.482	0.484	0.997	15.775	2.987	0.484	0.992
B2	3.403	0.487	0.476	0.988	13.688	1.960	0.476	0.996
B4	1.307	0.434	0.400	0.995	4.970	1.651	0.400	0.988
B5	3.943	0.489	0.492	0.989	14.988	1.858	0.492	0.987
B6	8.131	0.502	0.551	0.987	30.898	1.908	0.550	0.987
B8	4.182	0.491	0.500	0.993	15.067	1.768	0.500	0.990
B11	5.312	0.493	0.520	0.990	18.194	1.689	0.520	0.990
B14	4.079	0.499	0.464	0.990	15.506	1.897	0.464	0.994
B17	3.327	0.468	0.520	0.993	12.647	1.780	0.520	0.989
B20	3.515	0.481	0.510	0.996	13.362	1.828	0.510	0.990
B23	3.764	0.496	0.461	0.987	14.307	1.886	0.461	0.989