桂北硅质岩结构面抗剪强度研究

在广西壮族自治区桂林市天门村进行了硅质岩结构面强度的原位试验,结合现场调查,基于Barton模型,估算了硅质岩结构面抗剪强度。结果表明,硅质岩结构面的剪应力-位移曲线呈现出塑性变形的特征,剪切过程具有爬坡、空化、剪胀的特点。剪切曲线分为剪胀、剪断凸台和完全接触三个过程。结构面受剪力初期,剪应力上升较快,剪切位移随剪应力的增大而几乎呈线性增大,处于弹性状态;随着剪应力的不断增大,在剪切面处发生爬坡作用和啃断作用这两种力学效果;当将结构面上的凸台被啃断后,剪应力上升的梯度变小,直至峰值强度,处于完全接触状态。原位试验得到的抗剪强度参数与Barton模型计算的结果具有较好的一致性,但Barton模型参数的确定带有很强的主观性而造成的误差较大,导致其计算结果偏小,因此在没有经验值和相关工程参考的地区进行现场大剪试验是十分必要的,既保证了工程的可靠性,又避免过于保守,本次实验的结果为类似工程的取值提供了参考。

Research on shear strength of structural plane in silica rock of northern Guangxi

To measure shear strength of the structural plane of silica rock, in situ shearing tests are performed at the Tianmen village, Guangxi Zhuang Autonomous Region. Meanwhile, based on field investigations and the Barton model, the shear strength of this rock is also estimated. The test results indicate that shear stress-displacement curves have the characteristics of plastic deformation with climbing, cavitation and dilatancy, and the shear curves can be divided into three stages, i.e. ,dilatancy, cutting salient and complete contact. At the beginning of shearing, the shear stress rises rapidly and the shear displacement increases linearly with shear stress in the elastic state. With the increasing shear stress, climbing and cutting salient occur on the structural plane. After the cutting salient, the shear stress increases with decreasing gradient till reaching peak strength. The shear strength from in situ tests is largely consistent that from the Barton model, though the latter is slightly smaller. As the parameters determined by the Barton model are subjective to some extent with major errors, it is necessary to conduct in-situ shearing tests in a region without empirical values and reference projects, so that the reliability of the construction can be ensured and too much conservation can be avoided.