The excavation deformation mechanism and the seismic reinforcement effect evaluation of complex accumulation slope of a converter station in Southern Sichuan

The excavation deformation mechanism of the widely distributed complex accumulation slopes in the southwestern mountainous areas has a significant restriction effect on the construction of converter stations. To address the urgent needs of the converter station construction in Baihetan-Jiangsu UHV transmission project, the authors in this paper took the accumulation slope in the proposed station site as the research object, and adopted the deep displacement monitoring, in-situ test and FLAC3D numerical simulation methods to evaluale the excavation deformation mechanism of this accumulation slope and the seismic reinforcement effect under different design schemes and different pile parameters. Then the seismic reinforcement mechanism is analyzed. The results are as follows. ① The excavation of the complex accumulative slope of “multi-genetic type soil” in the converter station is prone to deformation, and the instability mode is “traction creep and tension failure mode”. ② The high and steep free face formed in the excavation process is the main factor leading to the accumulation slope deformation, and the high-water sensitivity of the accumulation slope soil is the internal inducement of the slope deformation aggravation after short duration heavy rainfall. ③ Under the two slope reinforcement schemes of circular anti-slide pile and rectangular anti-slide pile, the deformation amount of the slope body is significantly reduced, and the maximum deformation position in the slope body is located in the middle and back of the slope body. The stability coefficient of the accumulation body slope under natural and seismic conditions meets the design requirements. The use of rectangular anti-slide pile in the treatment of the accumulation body slope has higher anti-slide retaining and economic benefits. ④ The top deformation of the anti-slide pile is the largest under seismic condition, and the shear force and bending moment increase first and then decrease with the increase of seismic wave, and finally reach the maximum change trend. The maximum bending moment value is about 1/2 of the anti-slide pile body. The retaining design of slope should be combined with the distribution law of pile shear force and bending moment. The research results of this paper could provide some references for the design and construction of similar projects.