DEFORMATION CHARACTERISTICS AND CAUSE ANALYSIS OF EXIT SECTION(RIGHT SIDE TUNNEL) FOR TIANHE TUNNEL OF YA'AN-KANGDING EXPRESSWAY

This article collects the deformation characteristics of tunnel inside structures and outside slopes for right side tunnel of Tianhe Tunnel of Ya'an-Kangding Expressway. With assistance of supplementary investigation of geological data which including engineering geological mapping, engineering geological drilling, monitoring and measurement in tunnel, displacement monitoring of slope surface and deep displacement monitoring in drilling hole, the cause of deformation of the above tunnel section is thus discussed and analyzed. It reveals that such non-layered rock structure is influenced by vicinity tectonics and unfavorable structural plane of extroversion is developed. Especially, multi-stage eruptions and sedimentary cycle ever appeared in the local basalt tectonics and the eruption interval is long which leads to complex lithology, and in addition, pelitic siltstone or silty tuff with 4m thickness the most is found in the investigated area. Under the impact of adverse working conditions such as shallow cover, artificial excavation disturbance and precipitation, tectonic bias or bedding-like slippage is probably generated along the structural plane of extroversion and lithologic boundary. In the following treatment design and construction, according to the pre-survey for the characteristics and genetic analysis of the deformation, we designed the targeted deformation treatments for different sub-section, and continued to strengthen the construction monitoring and measurement. At the time of the announcement, the deformation section of the tunnel has been completed and the tunnel has been broken through. The monitoring inside and outside the cave revealed the overall stability of the slope. The tunnel structure was in a convergent state of deformation. So, it is necessary to reacquaint the structural characteristics and physical-mechanical properties of such massive rock which evidently has theoretical research value and practical guidance significance for similar engineering project.