Physical Modeling Investigation On Failure Mechanism of Layered Surrounding Rock And Deformation Characteristics Based On Digital Speckle Correlation Method

In rock mass engineering such as underground coal mine roadway, underground tunnel and water conservancy and hydropower chamber construction, layered rock mass is a type of surrounding rock mass that is often encountered. Due to the influence of bedding structural plane, its deformation process and failure mode are obviously different from that of intact enclosed rock mass. For the layered rock structure of roadway, the previous studies mainly focused on the situation of no support or single bolt support, but there is still a lack of experimental studies on the mechanical properties and failure laws of surrounding rock under different support methods. In this paper, the deep roadway and surrounding rock environment with a buried depth of 742-877m are taken as the engineering background, which is located in Anhui Province, China. Based on the similarity theorem and similarity criterion, river sand is used as aggregate, gypsum and cement are used as cementing material. According to the test results, 5:0.7:0.3, 6:0.3:0.7 and 4:0.5:0.5 of river sand, gypsum and cement were selected as the similar materials to simulate the surrounding rock of the roadway, and the bedding plane structure of the surrounding rock of the roof and floor near the roadway was designed by using the self-developed similar material physical model test bed. Digital Speckle Correlation Method (DSCM) is used to analyze the deformation evolution process of roadway surrounding rock under three supporting schemes: no-support scheme, bolt support scheme, and synergistic support of bolt and anchor cable. Based on this, the failure mode and instability mechanism of deep layered surrounding rock are further discussed. The results show that the tensile and shear resistance of laminated roof surrounding rock is weak, and the laminated roof is easily separated from each other at the bedding plane without support, resulting in bending deformation and bed separation. After adopting effective support, the laminated roof surrounding rock is transformed into a composite beam bearing structure, and the stability of surrounding rock increases. The research results have certain theoretical guiding significance and engineering application value for practical engineering.

Experimental Research on Bearing Characteristics of the Asphalt Pavement Containing Buried Pipeline

The bearing characteristics of the asphalt pavement structure are greatly influenced by buried pipelines. Improper treatment of buried pipelines would cause early damage to pavement structure. By the digital speckle correlation method (DSCM), the experimental research on bearing characteristics of the asphalt pavement containing buried pipe was carried out. The mechanical characteristics of the asphalt pavement structure are studied under four different pipeline burial conditions. The vertical displacement and strain values of each layer of the asphalt pavement structure are obtained under four operating conditions. The results showed that (1) the digital speckle observation test method can accurately obtain the displacement and strain values of each layer of asphalt pavement structure containing buried pipeline, and the application effect is good. Compared with the traditional contact strain measurement method, this method is simple and accurate and can provide effective analysis data for experimental research. (2) There exists an interlayer effect of the asphalt pavement structure. The vertical displacement value and the strain value are discontinuities and can suddenly change between two adjacent layers. At the same time, the vertical strain and the shear strain concentration phenomenon appear at the bottom of each layer, especially at the bottom of the upper layer and the subbase layer of asphalt. (3) Affected by the buried pipelines, the vertical displacement value of the asphalt pavement structure reduces, and the tensile and shear strain values of asphalt pavement structure increase. The subbase layer of asphalt is most affected by the buried pipelines, which accelerated the destruction of the asphalt pavement structure.