Complexity of the ground conditions and non compliance with basic assumptions in the trench stability analysis: a Case Study in Iran

摘要: Basic Insufficient Geological and geotechnical studies will be caused the inaccurate parameters for trench stability analysis. Therefore, as the first step, in the trench design, the special considerations for investigations and primary studies are very important. In the Portal of Sabzkuh Water Conveyance Tunnel design, despite the adequate geotechnical investigations, field studies have not been performed with appropriate accuracy, consequently a landslide and collapse is occurred in a part of the portal because of tunnel excavation. The site geology was predicted by taking soil samples from trench soil with underground and surface surveying inside of tunnel as well as trench site, that the Alternating layers of CL, CH, CL-ML, SC-SM and GP-GM with more than 55 degrees slope as well as a buried slide surface under alluvium was observed. But the primary assumptions used in the design by engineers were different from the results that were noted at the recent lines. In this paper, the importance of having a precise and predetermined schedule for selecting site location, Complexities of the ground conditions and its effects on the stability of the trench has been investigated.