膨胀性硬土/软岩劈理化规律及其结构强度特性研究

The strong consolidated or micro diagenetic clay material with the uniaxial compressive strength 0.3 - 1.5 MPa is neither rock nor soil, which has not been found in the standard at home and abroad. It is known as the hard soil/soft rock. The particularity of expansive hard soil/soft rock lies in the swell-shrink characteristic and cleaved crack interface effect. The crack has both relative orientation as rock and discontinuous feature as soil. The shear failure reflects the synthetic results of the physical effect and mechanical effect caused by the moisture and stress. The research object is expansive hard soil/soft rock with fragmentation in N1 and Q1 in Nanyang basin. The breakthrough point is fracture structural problem. The main research line is from moisture and stress, suction change, crack development to the structural strength damage. The fragmentation rules and the relationships between crack development and moisture-stress change will be deeply realized by carrying on the crack growth model experiment and neutron scattering experiment. The characteristics of material activation and crack activation will be researched after moisture and stress changing. The modern theory of unsaturated soil can be used in studying the dynamic relationship between crack development and structural strength change of hard soil/soft rock. The multiple-medium structure model from microcrack, mesocrack to macrocrack and structural strength damage function will be established to reveal slope disaster mechanism and failure mode of expansive hard soil/soft rock.

单轴抗压强度在0.3-1.5MPa的强固结或微成岩的粘土质地质体，是“岩”还是“土”，国内外无规范可依，被称为硬土/软岩。膨胀性硬土/软岩特殊性在于其物质的胀缩性与劈理化裂隙的界面效应，兼有岩石裂隙的相对定向性与土体裂隙的断续性特征，其剪切破坏是水力环境改变后物理作用与力学作用互为因果的综合效应。该项目以南阳盆地N1、Q1劈理化膨胀性硬土/软岩为研究对象，以“裂隙结构性问题”为切入点，以“水力环境—吸力变化—裂隙发展—结构强度损伤”为主线，通过裂隙生长模型试验与中子散射试验，系统认识硬土/软岩劈理化规律及水力环境变化与裂隙发展（扩展与闭合）的定量关系；探讨水力环境影响下的硬土/软岩物质活化与裂隙活化特征及其临界条件；采用现代非饱和土理论，研究硬土/软岩裂隙发展与结构强度变化的动态关系，建立“裂纹-微裂隙-裂缝”多重介质结构模型与结构强度损伤函数，揭示膨胀性硬土/软岩边坡灾变机制与破坏模式。

硬土/软岩是指介于岩石与土之间的“岩不岩、土不土”，“似岩非岩、似土非土”的过渡性岩土体。膨胀性硬土/软岩具有显著的胀缩性、碎裂性与低强度性。该类岩土体分布广泛，如南水北调中线工程、南昆铁路、北京客运西站等大型项目中均有出现，并引发了大量的工程灾害。.红层软岩具有独特的工程特性，是一种具有透水性弱、亲水性强，遇水易软化或膨胀，干湿循环条件下易崩解，抗风化能力弱等特性的硬土/软岩。本项目以云南地区的膨胀性红层软岩为研究对象，系统开展了水力环境影响下的膨胀性红层软岩的劈理化规律及其结构强度特性分析，掌握了影响红层软岩吸水性、膨胀性、崩解性的物质基础及其活化效应，分别从微观与宏观层次上，分析了红层软岩劈理化强度与变形特征及其受含水率、含石量、上覆压力制约条件下的粘聚力与内摩擦角变化规律，建立了红层软岩结构性与强度变化的动态关系，揭示了红层软岩典型的界面效应与结构效应。基于红层软岩结构强度损伤演化特性与结构强度损伤模型研究，采用数值分析方法，模拟了不同工况下红层软岩结构强度损伤与变形失稳模式，揭示了水力环境影响下的硬土/软岩边坡的灾变机制与破坏模式。.研究成果为膨胀性硬土/软岩的成因、分类、强度与变形及其工程应用奠定了理论基础，为膨胀性硬土/软岩边坡或地基的灾变防控提供了理论依据与技术支撑。