Abstract:
In the western part of China, the single-row-pipe layout was generally adopted for the freezing method of shaft drilling in weakly cemented rock layers. The frozen wall formed by this method showed significant heterogeneous characteristics. Meanwhile, the unfrozen rock mass around the frozen wall had a relatively high bearing capacity. Therefore, the design theory of frozen wall in deep alluvial layers in the central and eastern regions of China was no longer applicable to this type of stratum. To explore the mechanical properties of the single-row-pipe frozen wall in the weakly cemented rock strata in the western region of China, the temperature field of it was equivalently simplified to a triangular distribution, and the frozen wall was regarded as a heterogeneous material in which the elastic modulus
E and cohesion
c change linearly with temperature. Considering its interaction with the surrounding rock and based on different permafrost strength criteria, the calculation formulas for the elastic-plastic stress of the frozen wall were derived. Based on the obtained formulas, the mechanical properties of the frozen wall of the weakly cemented rock layer in the western part of China were calculated and analyzed. The results showed that the elastic ultimate bearing capacity of the heterogeneous frozen wall had increased by 81.6% after considering the interaction between the frozen wall and the surrounding rock. Based on the Mohr-Coulomb criterion, Drucker-Prager criterion, generalized Tresca criterion and the unified strength criterion of double shear, the plastic ultimate bearing capacity was calculated to increase by 140.9%, 140.4%, 146.9% and 150.9% respectively. It can be seen that the calculation results of the ultimate bearing capacity of the frozen wall have been significantly improved after considering the interaction with the surrounding rock. Under the condition of considering the interaction between surrounding rocks, the calculated value of the elastic ultimate bearing capacity of the heterogeneous frozen wall was 20.3% lower than that of the homogeneous frozen wall. Based on the above four strength criteria, it was calculated that the plastic ultimate bearing capacity of the heterogeneous frozen wall was reduced by 15.4%, 15.4%, 14.8% and 14.5% compared with the homogeneous frozen wall respectively. It can be seen that after considering the heterogeneous characteristics of the frozen wall, its calculated bearing capacity value was lower than that of the homogeneous frozen wall. The research results can provide a theoretical basis for the optimal design of frozen wall in weakly cemented rock strata in the western region of China.