Abstract: Due to its soft lithology, the red bed rock is generally characterized as the soft rock in the engineering geology industry. Under the action of the cold, hot temperature dry, wet moisture cycles, the rock mass is easy to be weathered and disintegrated in the water. The engineering geological characteristics of this rock mass are extremely poor, and the highway geo-hazards induced by the red bed rock slope is not easily to be detected. Due to the lack of corresponding highway slope maintenance technical specifications, it is difficult for maintenance personnel to accurately grasp the highway slope safety in the operation, which is to propose targeted maintenance measures at right time. This paper presents a stability evaluation case history of the expressway in Northeast Yunnan Province. Throughout the engineering geological survey, the characteristics of slope instability are evaluated. The failure of the highway slope was mainly induced by the failure of the slope protection measures and the presence of the excessive groundwater.  The stability development of the slope and the potential mitigation measures are also proposed.

Key words: operation period, expressway, red bed slope, ground anchors, instability factors