Experimental Study On The Evolution Law Of Mechanical Properties Of Layered Limestone Under Dissolution

The stability of engineering surrounding rock in karat areas is the primary issue for underground engineering construction.The predecessors revolved around the an-isotropic mechanical properties of layered limestone,the expansion and failure mode of limestone cracks,and the stress-dissolution coupling characteristics of soluble rock and underground surroundings.A lot of fruitful research work has been carried out on rock stability.The previous research results show that the influence of dissolution on the mechanical properties of layered limestone cannot be ignored.There are obvious differences in the mechanical properties of layered limestone under different bedding angles.However,the current experimental studies on the mechanical properties of layered limestone affected by dissolution are still insufficient.Therefore,through a large number of tests on the mechanical properties of layered limestone under the action of dissolution,this paper analyzes the law of the influence of dissolution on the mechanical properties of layered limestone under different unloading point states,different dissolution conditions,and different bedding angles,and combined with dissolution.The analysis of the mechanism of the influence of the action on the mechanical properties of the layered limestone has established the dynamic evolution law of the mechanical properties of the layered limestone under the action of dissolution,and the main conclusions obtained are as follows:1.According to the test purpose and technical route,the test plan was constructed and set,and related non-corrosive and dissolution-free layered limestone mechanical properties tests were carried out.According to the collated test data,it was found that: The axial stress-axial strain reference curve of layered limestone is similar to the axial stress-axial strain curve of limestone under the action of dissolution at different bedding angles,but there is a certain axial stress difference between the two value.2.According to the test results,the mechanical properties of the layered limestone under different unloading points are analyzed.It is obtained that the axial stress drop and the dissolution quality of the layered limestone at different bedding angles vary with the unloading point axis.The law of change to strain and its mathematical expression.The experimental phenomenon was analyzed and the cause was discovered: when the dissolution time is constant,the curve change shape of the axial stress drop with the axial strain of the unloading point under different layer inclination angles can be divided into four stages,the first stage(0<?*<0.3%),the difference between the mechanical properties and dissolution quality of layered lime stones with different bedding angles is basically zero;dissolution has basically the same effect on the mechanical properties of layered lime stones with different bedding angles.In the second stage(0.3<?*<0.6%),the difference between the axial stress drop and the peak drop of layered limestone with different bedding angles and their percentages ranges from 10 to 11 MPa,5 to 10%,and 11 to 30 MPa,10?15%;the range of dissolution mass and its percentage difference is 0?1g,0?0.2%;the axial strain at the unloading point is in dissolution on the mechanical properties of layered limestone.In the third stage(0.6<?*<0.8%),the range of the difference between the axial stress drop and the peak drop of limestone with different bedding angles and their percentages is 11-40 MPa,10-15%,30-65 MPa,15 ?20%;the range of dissolution mass and percentage difference is1?3g,0.2?0.6%;dissolution has the most significant impact on the mechanical properties of limestone with different bedding angles;the fourth stage(?*>0.8%),The sample enters the residual stage,and the range of the difference between the axial stress drop and the peak drop of the limestone with different bedding angles and its percentage is 0?10MPa,0?0.3%,0?11MPa,0?1%;dissolution quality and The percentage difference range is 0?0.2g,0?0.03%.3.According to the test results,the influence of the mechanical properties of the layered limestone under different dissolution conditions is analyzed,and the changes in the axial stress drop and the dissolution quality of the layered limestone with the dissolution time at different bedding angles are obtained.Mathematical relation expression.The experimental phenomena are analyzed and the reasons for this phenomenon are revealed: when the state of the unloading point is constant,the mechanical properties of the layered limestone with different dip angles are different under different dissolution times,and the dissolution time is0?4d.,The range of the difference between the axial stress drop and the peak drop of the layered limestone at different bedding angles and its percentage is 0?10MPa,0?1%,0?21MPa,0?10%;the dissolution quality and its percentage The difference range is 0?1.5g,0%;when the dissolution time is 4?8d,the difference between the axial stress drop and the peak drop of the layered limestone at different bedding angles and its percentage range is10?21MPa,1 ?5%,21?30MPa,10?12%;the range of dissolution mass and its percentage difference is 1.5?4.2g,0?0.12%;when the dissolution time is 8?16d,the axis of the layered limestone with different bedding dips The range of the difference between the directional stress drop and the peak drop and its percentage is 21?25MPa,5?10%,30?45MPa,12?15%;the range of the difference between the dissolution mass and its percentage is 4.2?5.1g,0.12?0.14%;With the increase of the dissolution time,the degree of crack opening of the layered limestone will gradually expand and gradually erode to the depth of the limestone sample,and the dissolution will gradually increase.