摘要
近水平岩层斜坡中的张性结构面的存在是产生平推式滑坡的前提。滑坡发生后,充水的张性结构面大幅张开拓宽形成拉陷槽。统计大部分中型、中层以上的平推式新滑坡发育特征后发现,拉陷槽的展布方向总体与盆地边缘构造带近于垂直。综合前人研究成果,通过水系分析反演四川盆地新构造应力场,得到滑坡拉陷槽展布方向与新构造主应力方向相近,认为其形成发育与新构造运动以来的应力场关系密切。构造应力场对平推式滑坡形成演化的影响主要表现在对岩体结构的改造、对结构面渗透性的控制和对斜坡水文条件的影响等方面。构造主应力方向的转换使与其近于平行的压(剪)性质结构面转变为张性,产生张裂延伸作用,扩大规模,结构面沿走向相互贯通,沿倾向跨层。并且使具有这种三维应力状态的结构面渗透性得到显著提高。结构面的渗透性、规模、连通性、张开度等同时被扩大。垂向和水平运移特征是平推式滑坡发生的主要因素之一,为滑坡的产生提供了形成演化条件。受构造应力场改造和影响的近水平岩层斜坡给水性和导水性得到改善,由于跨层张性结构面的存在,地下水有条件垂向运移到斜坡深处,与深层的软弱层产生物理化学作用,为形成规模和厚度更大的平推式滑坡提供条件。解释了中层、中型以上的平推式滑坡拉陷槽与构造主应力方向相近的缘由。
The existence of tensional structural planes in sub-horizontal rock slope is very important for the formation and evolution of the sub-horizontal translational landslides.After the occurrence of sub-horizontal translational landslides,the water-filled tensile structural planes can be widened to form a tension trough.We find that the distribution directions of the tension troughs of medium size,medium thickness or above sub-horizontal translational landslidesare almost perpendicular to the tectonic belt at the basin edge.On the bases of others’research results and the analysis of river system of Sichuan Basin inversion of neotectonic stress field,we find that the tension trough strike directionsare close to the principle stress direction of neotectonic stress field.We believe that the formation and development of these sub-horizontal translational landslides are closely related to the stress field of neotectonics.The influences of tectonic stress field on the formation and evolution of sub-horizontal translational landslides are mainly manifested in the transformation of rock mass structure,the control of permeability of structural plane and the influence of hydrological condition of slope.The change of principal stress direction makes the structural plane with compressive(shear)property close to parallel transform into tensile property,resulting in tensile crack extension and expansion of scale.The structural planes are connected with each other along the strike and crosses the layer along the dip.The permeability of the structural plane with the three dimensional stress state is improved remarkably.The permeability,scale,connectivity and opening of the structural plane are simultaneously expanded.The characteristics of vertical and horizontal migration are one of the main factors for the occurrence of sub-horizontal translational landslides and provide the formation and evolution conditions for the occurrence of landslide.Due to the existence of cross-layer tensile structural planes,groundwater is able to migrate vertically to the depth of the slope and have physical and chemical interactions with the deep soft layers,thus providing conditions for the formation of larger scale and thickness of sub-horizontal translational landslides.
作者
唐然
许强
范宣梅
TANG Ran;XU Qiang;FAN Xuanmei(School of Architecture and Civil Engineering,Chengdu University,Chengdu 610106,China;State Key Laboratory of Geohazard Prevention and Geoenvironment Protection,Chengdu University of Technology,Chengdu 610059,China)
出处
《工程地质学报》
CSCD
北大核心
2021年第5期1437-1451,共15页
Journal of Engineering Geology
基金
地质灾害防治与地质环境保护国家重点实验室团队重点课题(资助号:SKLGP2019Z002)。
关键词
四川盆地
平推式滑坡
构造应力场
张性结构面
拉陷槽
Sichuan Basin
Sub-horizontal translational landslide
Tectonic stress field
Tensional structure plane
Tension trough