Abstract
Shaft linings in thick weakly cemented stratum have the disadvantages of large deformation and repeated damage after repair. Considering the typical geologic characteristics and the failure characteristics of shaft linings, we establish a multilayer automatic deformation monitoring system in this paper, and the monitoring system can realize the real-time, continuous, and long-term dynamic monitoring on shaft linings. Based on the concrete strength failure criterion under biaxial compression and the analytical solution for spatially axisymmetric problem of thick-wall cylinders, the damage limit of the shaft lining in Xieqiao coal mine is obtained. Then, we choose three sections as the test area according to the typical damage forms of shaft linings to carry out the monitoring scheme on the auxiliary shaft in Xieqiao coal mine. The monitoring results show that the extreme value of the shaft lining deformation is 2.369 mm. And the shaft lining located in the border between the floor aquifer and the bedrock generates the most severe deformation, which is about 89.4% of the deformation limit. The shaft lining deformation increment fluctuates in certain range, which belongs to elastic deformation. Finally, we inverse the stress state according to the deformation value of the shaft lining, and the obtained additional stress is found to be lower than the ultimate compressive strength. Long-term project practice confirms that the deformation monitoring results can reflect the real stress condition of the shaft lining and that the monitoring system can realize the real-time dynamic evaluation for the status of the shaft lining.
Highlights
Shaft linings in thick weakly cemented stratum have the disadvantages of large deformation and repeated damage after repair
Based on the concrete strength failure criterion under biaxial compression and the analytical solution for spatially axisymmetric problem of thick-wall cylinders, the damage limit of the shaft lining in Xieqiao coal mine is obtained. en, we choose three sections as the test area according to the typical damage forms of shaft linings to carry out the monitoring scheme on the auxiliary shaft in Xieqiao coal mine. e monitoring results show that the extreme value of the shaft lining deformation is 2.369 mm
Analysis of Monitoring Results. e deformation monitoring system of the auxiliary shaft in Xieqiao coal mine started running after the installation test in November 2014, and the deformation was monitored in different time periods
Summary
Xieqiao Coal Mine is located in Xieqiao Town, Yingshang County, Fuyang City, Anhui Province of China. e thickness of the weakly cemented loose layer (topsoil layer) is 310.5 m, and the bottom aquifer has a thickness of 60 m. E thickness of the weakly cemented loose layer (topsoil layer) is 310.5 m, and the bottom aquifer has a thickness of 60 m. E bedrock of Xieqiao coal mine is covered by thin Cenozoic loose layer with a thickness of 390.35 to 509.10 m. E main mineral composition of the weakly cemented loose layer is the “secondary mineral” (the products of rock weathering), ranging in the thickness from 50 to 500 m. The variation in strength index of saturated clay is not linear with the increase of formation depth in weakly cemented stratum [33]. The location with the maximum strength difference along the shaft depth is the most prone to deformation and failure
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