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卸荷作用广泛存在于人类的工程活动和地质作用过程中,岩体在卸荷条件下的力学特性研究一直是工程界探讨的热点问题之一。根据实际边坡工程开挖后应力变化状态确定试验方案,进行了砂岩三轴卸荷破坏试验,研究了卸荷状态下岩体的应力应变特征、破坏特征及力学参数变化规律,并与加载破坏试验数据进行了对比分析。试验结果表明,卸荷破坏时岩样变形模量随着卸荷量的增加可降低5%～42%左右,二者之间的关系可用指数函数拟合;卸荷破坏时岩体的峰值应变随围压线性增长,残余应变与围压无明显关系;相比于加载破坏,卸荷破坏时岩体凝聚力c值降低了4%左右,内摩擦角?增加了12%左右;卸荷速率对岩样强度和变形参数有较大影响;卸荷条件下岩体破坏具有沿卸荷方向强烈扩容特征,主要表现为张剪破坏,并伴随有环向裂纹,初始围压越高,卸荷程度越强烈,岩体的破碎程度越高。
Unloading is widely existed in human engineering activities and geological processes. The study of mechanical properties of rock mass under unloading has been one of the hot topics in engineering. According to the actual stress state of slope engineering after excavation to determine the test program, the sandstone triaxial unloading failure test was carried out to study the unloading state of rock mass stress and strain characteristics, failure characteristics and mechanical parameters change law, and load failure Test data were analyzed. The experimental results show that the deformation modulus decreases about 5% -42% with the increase of unloading load when the unloading failure occurs, and the relationship between them can be fitted by exponential function. The peak strain of rock mass during unloading failure With the linear increase of confining pressure, there is no obvious relationship between residual strain and confining pressure. Compared with loading failure, c value of rock mass decreases about 4% and internal friction angle increases about 12% Rock strength and deformation parameters have a greater impact; under unloading conditions, rock mass destruction has a strong expansion along the unloading direction, which is mainly characterized by Zhang Shek failure and accompanied by circumferential cracks, the higher the initial confining pressure, the unloading degree The more intense, the higher the degree of rock crushing.