川藏铁路交通廊道某大型古滑坡成因及失稳模式分析

doi:10.19657/j.geoscience.1000-8527.2021.017

摘要/Abstract

摘要：

川藏铁路沿线地形地貌复杂,构造活动强烈,地质灾害频发,其中古滑坡复活问题是威胁川藏铁路建设和运营的严重隐患之一。位于四川康定市的某古滑坡体,距原规划的川藏铁路大桥仅100 m,通过工程地质测绘和钻孔勘探,分析该古滑坡的发育特征与成因机制;并利用二维有限元软件,对古滑坡可能的失稳模式进行预测。结果显示:古滑坡边界清晰,滑坡体积约118万m ³,主要沿基覆界面滑动,局部变形破坏强烈;发育多级拉张裂缝;天然工况与降雨工况下处于稳定状态,地震工况下处于不稳定状态;潜在破坏部位为边坡中部碎石土堆积体后缘,滑动面即沿着碎石土与全风化岩体的接触面,一旦复活将严重威胁铁路大桥的运营与安全。

关键词: 川藏铁路, 古滑坡, 失稳模式, 形成演化, 高寒山区

Abstract:

Sichuan-Tibet railway is vulnerable to serious geological hazards, especially where the topography is complex and tectonic activities are intense. The reactivation of paleo-landslides is one of the serious threats to the construction and operation of the railway. A paleo-landslide is located in the Kangding city, only one hundred meters away from the proposed Sichuan-Tibet railway. On the basis of the analysis of characteristics and formation mechanism using engineering geological mapping and exploration drilling, this study predicts its potential failure mode. The results are listed as follows. The large-scale paleo-landslide mainly slides along the bedrock-overburden discontinuity with strong partial deformation and develops multi-level tensile cracks. The stability scale is stable in the natural and rainy condition, but becomes unstable when earthquake occurs. The potential landslide failure sites are the trailing edges of gravel soil in the middle of the slope, while the potential sliding surface is the interface between the debris rock soil and the fully-weathered rock body.

Key words: Sichuan-Tibet railway, paleo-landslide, failure mode, formation and evolution, alpine area

中图分类号:

P642

王家柱, 高延超, 冉涛, 铁永波, 张凡. 川藏铁路交通廊道某大型古滑坡成因及失稳模式分析[J]. 现代地质, 2021, 35(01): 18-25.

WANG Jiazhu, GAO Yanchao, RAN Tao, TIE Yongbo, ZHANG Fan. Analysis of Genetic Mechanism and Failure Mode of a Large Paleo-landslide in Sichuan-Tibet Railway Transportation Corridor[J]. Geoscience, 2021, 35(01): 18-25.

图/表 8

图1 四川康定某古滑坡区地质构造与全貌图 (a)研究区地质构造;(b)滑坡区断裂分布;(c)滑坡全貌

Fig.1 Geological structure and full view of the paleo-landslide in Kangding, Sichuan

图2 滑坡区工程地质平面图

Fig.2 Engineering geologic plane of the paleo-landslide

图3 滑坡变形破坏特征 (a)Ⅰ1区后缘下错;(b)Ⅰ1区坡表积水;(c)Ⅰ2区滑坡变形破坏特征;(d)Ⅰ3区滑坡变形破坏特征

Fig.3 Deformation and failure characteristics of the paleo-landslide

图4 1-1'工程地质剖面(a)及其有限元计算模型(b)

Fig.4 Engineering geologic profile of 1-1' (a) and its FEM model (b)

表1 岩土体主要物理力学参数

Table 1 Physical and mechanical parameters of the rock and soil

岩土材料	密度/ (kg/m³)	弹性模量 /MPa	泊松比	黏聚力 /MPa	内摩擦角 / (°)
碎块石土	2 100	350	0.30	0.05	38
卵砾质粉质黏土	2 000	300	0.32	0.1	37
全风化岩体	2 200	500	0.28	0.2	40
强风化岩体	2 300	2 000	0.25	1	45
弱风化岩体	2 600	5 000	0.23	2	55

图5 1-1'剖面稳定性计算结果

Fig.5 Stability of profile 1-1'

图6 天然工况和暴雨工况下1-1'剖面位移图 (a)天然工况下(SRF=2.038);(b)暴雨工况下(SRF=1.639)

Fig.6 Slope displacement maps of profile 1-1' under natural and rain condition

图7 地震工况下1-1'剖面数值模拟计算结果(a)地震工况下1-1'剖面剪应变;(b)地震工况下(SRF=0.985);(c)地震工况下1-1'剖面塑性区分布图

Fig.7 Numerical simulation results of profile 1-1' under earthquake condition

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