Destructive Influence of Technogenic Factors and Precipitations on Landslide Support Structure

Abstract

The investigated landslide occurred after mass excavation at the toe of the slope due to construction of an aqua park and heavy rainfall in November 2014. The induced slope instability affected the only road linking the village of Gorni Voden with the town of Asenovgrad. Immediately after the landslide occurrence an engineering-geological site investigation had been carried out. It was followed by proposal for remediation measures. The landslide has an elongated shape with a maximum width of up to 60 m, length 140 m and area of approximately 8000 m². The volume is above 20,000 m³. The damaged length of the road was 35 m. The investigation established the geological composition of the slope, key elements of the landslide, its mechanism, physical and engineering properties of the soil and the groundwater conditions. The reinforcement design consists of anchored pile retaining wall and drainage system. Due to the delay in construction, during the following warm and rainy winter the landslide increased its area more than two times. Subsequently, after the anchored pile retaining walls were constructed, the builder of the new aqua park made a new deep excavation downslope from the reconstructed road section. This excavation destabilized the landslide once again leading to cracks formation on the slope and increasing the depth of the sliding surface. The landslide body has been saturated through the open cracks by the following rainfall, soil consistency has been changed and the shear strength has decreased. The landslide process has progressed upwards and the new sliding surface reached the anchored pile retaining wall and compromised it locally. This paper discusses the remediation design proposed after the landslide occurrence, its implementation and the factors influencing the consequent structural damages on retaining wall due to loss of overall stability.