Analysis of Stratigraphic Subsidence Caused by Sand Leakage in Tunnel Lining

According to the phenomenon of stratigraphic subsidence caused by sand leakage in tunnel engineering, the process of sand surging was compared with the process of material discharging in the silo, the sand in the flat-bottom silo and its discharge bore and sand was used to simulate the lining structure, lining cavity and the sand in the stratum behind the lining in the tunnel engineering respectively. Through the design of indoor sand leakage experiment system, sand leakage experiment was carried out in the flat-bottom silo to discussed that under the condition of constant bore diameter, the influence of different thickness-to-span ratio on sand settlement range, settlement trough, the amount of sand leakage, and the influence of different bore size on sand leakage velocity under the condition of different bore diameter, and the critical crack ratio and flow pattern of sand were analyzed. The results showed that when the diameter of the bore was constant, the influential radius of settlement was basically linear with the thickness-to-span ratio as the soil thickness increased, and the proportion of sand loss to the total sand also increased, when the diameter of bore was different, the leakage velocity increased with the increase of the bore diameter, and the function relation could be described by the quadratic curve. There was a critical state for the collapse of sand, when the ratio of the diameter of the bore to the diameter of the sand particles did not exceed this critical state, the sand would form a stable soil arch structure above the bore, preventing the further development of sand leakage; when the collapse of sand occurred, the larger the diameter of the underground cavity, the greater the depth of the erosion, the greater impact on the ground.