三峡地区泥灰质岩石在岩溶和风化过程中力学性质的变化

VARIATION OF MECHANICAL PROPERTY OF MARLITE IN PROCESS OF KARSTIFICATION AND WEATHERING IN THREE GORGES REGION

三峡地区泥灰质岩石的岩溶问题是新近发现的重大工程地质问题。泥灰质岩石具有灰岩和泥岩双重特性,在其中的钙质成分被溶蚀的同时,泥质成分遭受风化,从而使岩性和岩石结构发生变化,岩石的力学强度不断降低,有的岩石已属于较软岩范围。岩溶、风化形成的松散土层具有易滑性,易于发生变形破坏。泥灰质岩石作为移民迁建地基可能因溶蚀、风化而发生地质灾害。防止水向地基的入渗是防治该区地质灾害的关键。

The newly discovered karst problem of marlite in Three Gorges region is an important problem in engineering geology. Marlite is of both the properties of limestone in which CaCO3 can be dissolved and mudstone in which mud component can be weathered,which brings about the variation of the rock contents and textures. With the variation,the indexes of mechanical property of the rocks,such as uniaxial compressive strength (Rc),deformation modulus (Eb),elastic modulus (Et),wave velocity (Vp and Vs),dynamic elastic modulus (Ed) and dynamic shear modulus (Gd) drop gradually,so that some rocks belong to relatively soft rock by national standard. The loose soil layers brought about by dissolution and weathering,with the increase of montmorillonite content (S),enlargement of specific surface area (B),high liquid limit (wl),high plastic limit (wp),high plastic index (Ip),strong pro-water property,expansive property and low shear strength (c,j),are easy to be slided and deformed. As the foundation of project for population resettlement,there may occur geo-hazards,such as landslide,collapse,debris flow,uneven subsidence,fissure and cave-in by dissolution and weathering. So it is necessary to use flexible ideas to treat the stability of the foundation,and the key measure to control the geo-hazards is to keep the foundation from saturation.