岩溶区薄层泥化夹层剪切强度弱化微观机理及现场测试新方法

Guizhou Province is located in the central area of karst regions in China. The special geological environment and large numbers of engineering construction have resulted in frequent occurrence of landslide, causings serious losses and threats. Weakening strength of muddy interlayer is one of the main factors causing these disasters.The existing analysis of the research results of thin argillaceous intercalation in Karst area, mostly based on empirical judgment and conventional test methods, and the evolution law of engineering characteristics has not been fully grasped. This project uses scanning electron microscopy (SEM), nuclear magnetic resonance (NMR) and other testing methods to analyze the essence of weakening strength of thin argillaceous intercalation in karst area from a microscopic point of view and reveal the formation mechanism. At the same time, it is difficult to sample thin interlayer in conventional mechanical test, and achieve real mechanical parameters for remolding samples. Based on the theory of bending element, a testing device for shear strength of muddy interlayer is developed. According to the results of indoor and outdoor tests, the correlation equation between strength and shear wave velocity, water content and confining pressure is established. The results scientifically reveal the nature and formation mechanism of strength weakening of muddy interlayer, and provide a theoretical basis for studying the evolution process of landslide deformation and instability, stability assessment, etc. The new bending element device can quickly test the strength of original muddy interlayer in situ, and solve the problems of difficult sampling, difficult parameter acquisition and poor reliability in conventional tests.

贵州省处于我国岩溶地区的中心地带，特殊的地质环境以及大量的工程建设，致使边坡（滑坡）屡有发生，造成严重损失和重大威胁。泥化夹层强度弱化是致灾的主要因素之一。目前泥化夹层强度弱化研究主要是以经验性判断和常规试验手段居多，尚未深入掌握其工程特性的演化规律。本项目以黔西地区为主要调查、试验场地，采用扫描电镜（SEM）、核磁共振（NMR）等多种测试手段，从微观角度分析岩溶区薄层泥化夹层强度弱化的本质，揭示形成机理；同时针对薄层夹层试验难取样，重塑试样难以获取真实的力学参数，原位试验周期长且费用高等问题，探索性地研制泥化夹层剪切强度的弯曲元测试装置，并根据室内外试验的成果，建立强度计算的相关性方程。该成果揭示了泥化夹层强度弱化本质和形成机理，为研究边坡变形失稳演化过程，稳定性评价等提供了理论基础；弯曲元新装置可快速进行现场测试原状泥化夹层强度，解决了以往常规试验中存在的取样难，获取参数难，可靠性差问题。

泥化夹层是溶蚀地区岩体工程中常见的具有特殊力学性质的弱化结构体，通常由于对其力学性质的研究够不够深入而导致大量工程失稳破坏，造成巨大损失。针对2个亟待解决的问题：薄层泥化夹层强度弱化的本质是什么？如何快速准确现场测试泥化夹层强度参数？本基金项目以岩溶区的层间薄层泥化夹层为研究对象，通过剪切试验、扫描电镜（SEM）、核磁共振（NMR）等，黏土含量约为60%，主要是伊利石、高岭石以及伊蒙混层，其次是石英、钾长石、钠长石，其它成分则较少；重塑试样力学参数随含水率的增加而呈现非线性降低，整体呈现较大凹形曲线，含水率为28.4%为拐点，原状试样力学参数同样随着含水率增加呈非线性降低，含水率为32.5%为拐点，重塑试样与原状试样相比，其强度参数存在一定的差异，其中内摩擦角φd取值范围为（0.2~0.78）φr，且随着含水率的增加呈现先增大后减小，整体呈现两段小中间大的特征。扫描电镜（SEM）、核磁共振（NMR）试验获取泥化夹层微观演变的特征，并进行量化处理，分析强度弱化的本质和揭示形式机理。结果显示，泥化夹层剪切强度弱化本质是颗粒的组合形态及孔隙结构演化结果。建立微观结构的方程式，量化展现宏观强度的演化规律。依据弯曲元振动剪切波在不同的物质特征反映出的差异性规律，研制适合现场测试泥化夹层剪切强度的新装置，建立获取泥化夹层力学参数的计算方法。研究成果揭示了泥化夹层剪切强度弱化机理，并建立的相关的计算模型，对相关工程的安全评价及治理提供了科学依据。