含层间剪切带的层状复合岩体质量分级

Quality classification of stratified composite rock mass with interlayer shear zones

层间剪切带作为一种特殊的软弱结构面,常常构成威胁工程岩体稳定性的控制性因素。分析常用岩体质量分级方法对于层间剪切带的初步认识和存在的问题,提出从岩体结构控制论观点出发,在考虑层状岩体结构类型的基础上,根据层间剪切带发育规模特征及其对层状复合岩体稳定性的影响机制,建立含层间剪切带的层状复合岩体质量分级与评价方法:(1)对于厚度大于10 cm、连续性好、有一定规模的层间剪切带,将其划定为独立的剪切错动型软弱夹层结构,根据层间剪切带的抗剪强度参数,对其单独进行质量分级与评价。(2)而对于厚度小于10 cm、规模相对较小的层间剪切带,特别是泥化夹层,则将其作为折减因素,对含层间剪切带的层状复合岩体质量分级进行弱化处理,建立含层间剪切带的层状复合岩体质量分级修正BQ方法。以黄河中游地区某大型水利枢纽工程为例,利用建立的修正BQ方法研究得到坝址区2个层间剪切带较发育的勘探平硐围岩质量分级评价结果,并将其与RMR法、Q系统法以及HC法得到的岩体质量分级结果进行对比分析和相关性研究,验证含层间剪切带的层状复合岩体质量分级方法的有效性。

As a special weak structural plane,interlayer shear zone often forms the control factor which threatens the stability of engineering rock mass. The preliminary cognition and existing problems of main quality classification methods of rock mass about interlayer shear zones are analyzed. Based on the viewpoints of control by rock mass structure and consideration of layered rock mass structure types,according to the size characteristics of interlayer shear zones and their impact mechanism on the stability of stratified composite rock mass,the quality classification and evaluation methods of stratified composite rock mass with interlayer shear zones are established.（1） The interlayer shear zones with good continuity and bigger dimension,whose thickness is more than 10 cm,are set as independent weak interlayer structure of shear dislocation. For this circumstance, the quality classification and evaluation of stratified composite rock mass with interlayer shear zones are carried out separately,according to the shear strength parameters of interlayer shear zones.（2） The interlayer shear zones with smaller dimension,especially the siltized interlayers whose thickness is less than 10 cm,are regarded as the reduction factors. The modified BQ method of quality classification of stratified composite rock mass with interlayer shear zones is founded by weakening treatments. The quality classification results of surrounding rock mass at two exploration adits with obvious interlayer shear zones in the dam site are obtained by the modified BQ method,taking some large-scale water control project in the Middle Yellow River. By comparison and relevant analysis with RMR,Q,and HC methods,the validity of the modified method of stratified composite rock mass quality classification with interlayer shear zones is verified.