软硬互层岩体变形破坏机制物理模拟试验研究

Physical simulation test on deformation and failure mechanism of soft and hard interbedded rock masses

为研究软硬互层结构层状岩体的变形破坏与拉-剪断裂机制,采用物理相似模拟手段预制不同层面倾角和软硬层厚比的试样,进行单轴压缩试验,并对试验应力-应变曲线和试样表面裂纹进行分析,得到以下结论:(1)单轴压缩下试样峰值强度和杨氏模量,随层理面倾角β的增加先减小后增大,随软硬层厚比k的增加有降低趋势。(2)由于沿层面的局部剪切滑移,倾角为30°~45°试样的应力-应变曲线在加载初期有一个明显的应力突降点,这是软硬互层岩体应力-应变曲线一个独有的多峰型特征。另外相比于已有层状岩体破坏模式,发现一种软层压碎、硬层穿层拉破坏的新模式。(3)采用表面裂纹图像提取方法,首次给出在层面倾角β和软硬层厚比k控制下,试样表面裂纹特征演化的玫瑰花分布图。同时研究拉、剪断裂的破坏机制和裂纹的分布占比以及对试样破坏模式的影响规律。研究得出,层面倾角β控制裂纹的扩展方向;软硬层厚比k决定拉、剪破坏的占比。沿层面的剪切滑移、硬层中的拉伸断裂以及软层中的压碎破坏,是导致试样变形破坏的3个主要因素。当层理面倾角β在30°~45°附近时,层面发生剪切滑移,剪裂纹增多。当层理面倾角在0°和90°附近时,试样在穿层或沿层方向发生拉伸破坏,剪裂纹减少。

In order to study the mechanical properties and tensile-shear failure mechanism of soft and hard interbedded rock masses,the specimens with different layer dip angles and layer thickness ratios using a physically similar simulation method and conducted uniaxial compression tests were prefabricated,and the following conclusions were obtained:(1)the peak strength and Young's modulus of the specimens decrease first and then increase with the increase of the dip angleβ.They decrease with the increase of soft-hard layer thickness ratio k.(2)Due to the local shear slip along the bedding plane,the stress-strain curves of specimens with a dip angle of 30°-45°have a large stress abrupt drop point at the early stage of loading.This is a unique multi-peak characteristic of the stress-strain curve of soft and hard interbedded rock masses.In addition,compared with the existing laminated rock failure modes,a new failure mode was found,that is,soft strata compression damage and hard strata tensile damage across the bedding plane.(3)Using a method of crack image extraction,the rose distribution map of crack characteristic evolution on the samples surface is given for the first time under different dip anglesβand thickness ratio k.At the same time,the failure mechanism of tensile and shear cracks and the distribution proportion of cracks were studied,along with the influence on the specimen's failure mode.It is believed that the dip angleβcontrols the crack propagation direction,and the thickness ratio k determines the proportion of tensile-shear failure.Shear slip along the layer,tensile fracture in the hard layer and crushing failure in the soft layer are the three main factors leading to the deformation and failure of the samples.When the bedding plane dip angleβis around 30°-45°,the shear slip occurs at the bedding plane and the shear cracks increase.When the dip angles are near 0°and 90°,tensile failure occurs in the through layer or along the layer direction,and the shear cracks decrease.