溶蚀作用对层状灰岩平行和垂直层面力学性质影响试验研究

Experimental study on influence from karstification on mechanical properties of parallel and vertical bedding-planes of layered limestone

为研究溶蚀作用对不同层面方向灰岩轴向力学性质间的影响差异,选取平行与垂直两种层面方向的灰岩进行室内试验,开展了不同试验条件的溶蚀作用下层状灰岩单轴压缩力学试验,根据试验结果分析并量化了溶蚀作用下层状灰岩力学性质的差异与变化规律。试验结果显示,溶蚀作用对两种层面方向的灰岩在轴向应力上所造成的影响相似但有差异,垂直层面方向受到的溶蚀影响更强。分别建立了溶蚀作用下两种层面方向的灰岩力学性质变化规律的相关表达式,据此进行试验数据分析,结果表明,在不同的裂隙状态下平行与垂直层面方向的灰岩的轴向应力特性受溶蚀作用的影响存在差异。即:在一定溶蚀时间里,当裂隙处于细观状态时,两者的轴向应力降及其百分比,以及轴向应力降峰值及其百分比之间的差值范围为0,溶蚀作用对两者的影响基本相同;随着裂隙逐渐扩大,两者上述4种量值的差值范围分别为0~10 MPa、0~10%和0~40 MPa、0~15%,溶蚀作用对两者的影响开始出现差异;当形成贯通裂隙时,两者上述4种量值的差值范围分别为10~30 MPa、10%~15%和40~60 MPa、15%~20%,溶蚀作用对两者的影响差异最为显著;此后试样被破坏,溶蚀作用对两者的影响变得不明显;在一定的卸载点轴向应变下,灰岩裂隙随着溶蚀时间的增加逐渐增大,同时溶蚀效应对层状灰岩的影响逐渐减弱。研究成果为进一步研究溶蚀作用下层状灰岩力学特性的变化规律奠定了试验依据以及理论基础。

In order to study the difference among the influences from karstification on the axial mechanical properties of limestone in different bedding directions,the bedding-planes in both the parallel and vertical directions are selected for the relevant indoor experiments,and then the uniaxial compression mechanical experiments of the layered limestone under the karstification are made for different experiment conditions.In accordance with the experiment results,the difference and changing law of the mechanical properties of the layered limestone under the karstification are analyzed and quantified.The experiment results show that the influences from the karstification on the axial stresses of the limestones in the two bedding directions are similar,but have difference;in which the influence from the karstification on the bedding-plane in vertical direction is stronger.Therefore,the relevant expressions for the changing laws of the mechanical properties of the limestones in both the bedding-plane directions are established respectively.On the basis of this,the relevant experiment data analysis is carried out and the result shows that the difference of the influence from the karstification on the axial stress characteristics is there between the limestones in both the parallel and vertical directions under different statuses of fissure.That is to say,when the fissure is in mesoscopic status,the difference value ranges between the axial stress drops and the percentages as well as the peak values of the axial stress drops and their percentages are 0 during a certain time of the karstification,while the influences from the karstification on both of them are basically the same as well.Following with the gradually enlarging of the fissure,the difference ranges of the above-mentioned values for both of them are 0~10 MPa,0~10%and 0~40 MPa,0~15% respectively,and then the influences on both of them start to be different.When penetrated fissure is formed,the difference ranges of the above-mentioned values for both of them are 10~30 MPa,10%~15% and 40~60 MPa,15%~20% respectively,thus the d ifference between the influences from the karstification on both of them are most significant.Afterwards,the experiment sample is destructed and the influence from the karstification on both of them becomes unobvious.Under a certain unloading point axial strain,the fissure of limestone is to be gradually enlarged along with the increase of the karstification time,meanwhile the influence from the karstification on the layered limestone is to be gradually weakened.The study result lays an experimental and theoretical basis for the further study on the changing law of the mechanical properties of the layered limestone under the effect of karstification.