真三轴加卸载应力路径对原煤力学特性及渗透率影响

Influence of true triaxial loading-unloading stress paths on mechanical property and permeability of coal

深部煤炭资源开采过程中,由于地应力和工程扰动的影响,煤岩体常处于三向不等压的真三轴应力状态(σ1>σ2>σ3),而采用常规三轴(σ1>σ2=σ3)的加载应力路径难以反映煤岩体的实际受力状态。为此,利用自行研制的"多功能真三轴流固耦合试验系统",研究了真三轴加卸载应力路径下原煤力学特性及渗透率演化规律。结果表明:真三轴加卸载应力路径对原煤的变形、强度特性及渗透率演化规律有重要影响。与CCT加载应力路径相比,LUT,LUUT应力路径下原煤峰值强度降低;真三轴加卸载应力路径下原煤八面体剪应力与有效平均正应力之间存在线性关系。真三轴加卸载应力路径下的原煤破坏方式均为拉-剪复合破坏。此外,真三轴加卸载应力路径对原煤渗透率演化规律有显著影响。

During the process of deep coal mining,coal seams are generally under the true triaxial stress state（σ_1σ_2σ_3）,which is influenced by the crustal stress and strong excavation disturbance.The results of conventional traxial stress tests（σ_1σ_2=σ_3） could not correctly describe the in-situ condition.In order to more accurately replicate the stress environment of coal seams,the self-developed new multi-functional true triaxial fluid-solid coupling experiment system was applied to investigate the mechanical properties and permeability evolution of coal under true triaxial loading-unloading stress paths.The results show that the true triaxial loading-unloading stress path has a great influence on the deformation and failure behavior,strength characteristics,permeability evolution.Compared with the CCT stress path,the LUT and LUUT stress paths reduced the peak strength of coal.The octahedral shear stress and the effective mean normal stress of coal can be linearly fitted.The failure modes of coal under different true triaxial loading-unloading paths were composite tensile-shear failure.Additionally,true triaxial stress path has great influence on the permeability evolution of coal.