Effects of excavation support of deep and large foundation pit on gravel stratum on adjacent existing road

doi:10.16265/j.cnki.issn1003-3033.2025.01.0025

Abstract

Abstract:

To prevent accidents and disasters, such as the collapse of existing roads nearby, caused by deep and large foundation pit excavation and support, it is necessary to ensure the safe operation of adjacent roads during the construction of deep and large foundation pits. Taking a deep and large foundation pit project near a city trunk road in Kunming as an example, on the basis of in-depth research at the site, the three-dimensional finite element numerical simulation software-new eXperience of GeoTechnical analysis system(MIDAS GTS NX) is used for simulation and calculation, and combined with on-site monitoring, to analyse the force and deformation characteristics of the foundation pit support structure and the deformation characteristics of the adjacent existing road under the existing excavation and support scheme. The study results indicated that the forces and deformations of the supporting piles and anchor cables were within design limits after the foundation pit excavation and support were complete. The displacement near the existing road increased with the increase of pit excavation depth, and become stable after the excavation was completed. The maximum deformation of the existing road occurred at a position 2.5 times the excavation depth from the foundation pit boundary. Furthermore, the deformation did not reach the alarm threshold for road displacement caused by foundation pit excavation. Thus, the existing support scheme can ensure the safety of both the foundation pit and the adjacent road.

Key words: rounded gravel stratum, deep and large foundation pit, excavation support, existing road, deformation impact, site monitoring

CLC Number:

X948

GUO Yanhui, MA Rui, MAO Shilin, QIAN Yong, DING Mingzhong, SONG Qin. Effects of excavation support of deep and large foundation pit on gravel stratum on adjacent existing road[J]. China Safety Science Journal, 2025, 35(1): 94-102.

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地层	弹性模量/ MPa	泊松比	容重/ (kN·m^-3)	黏聚力/ kPa	内摩擦角/ (°)	三轴割线刚度/ (kN·m^-2)
杂填土	7.0	0.28	18.7	19.5	8.5	3 850
泥炭土	12.1	0.40	13.2	20.0	6.0	6 655
圆砾土	196.7	0.46	19.4	9.4	41.0	108 185
粉质黏土	16.0	0.30	19.0	40.0	12.0	8 800

结构形式	弹性模量/MPa	泊松比	容重/(kN·m^-3)
锚索	195 000	0.30	78.5
支护桩	31 500	0.20	25.0
压密注浆	25 000	0.30	23.0
高压旋喷加固、挡土墙	31 500	0.20	25.0

现场监测项目	布设方法	数量	监测点编号
道路竖向位移	间距为6m,布设10排测点,每排共布设8个	80	F1-1—F1-8、F2-1—F2-8、F3-1—F3-8、F4-1—F4-8、F5-1—F5-8、F6-1—F6-8、F7-1—F7-8、F8-1—F8-8、F9-1—F9-8、F10-1—F10-8
桩顶水平位移	每隔15~20 m布设一个	5	WY63、WY64、WY65、WY66、WY67
桩顶竖向位移	每隔15~20 m布设一个	5	W63、W64、W65、 W66、W67
锚索内力	布设在具有代表性部位,数量为总数的1%~3%,每层竖向保持一致	6	M1-032—M6-032