Damage Mechanism And Countermeasure Of Excavation Slope In Highway In Southwest Yunnan Province

In accordance with State Road G213 Da Kaihe-Mohan. On the base of the actual survey on ther Highway of Southwest Yunnan, the Regional context, Regional topography, Engineering geological conditions, Hydrogeological conditions, Engineering geological characteristics of the red bed, and the impact of tropical rainforest climates to the red bed have been analyzed. And then a portion of the interior Simulation and Rock mechanics experiments have been finished. We can see that impact of special tropical rainforest climate on Red bed highway slope stability in the area by comparing between laboratory experiments and field conditions. The following conclusions:(l)Affected by heavy rainfall erosion effects, topography of the study area is small; Affected by the strong geological structure of the study area, stratigraphic occurrence in the study area changed greatly. Intense tectonic caused fault and fold growth in the study area, there are more times across the fault, fold belt along the highway.Red layer distribution in the study area is mainly in the northern and southern regions along the highway, the central region is less exposed, strata mainly for the Permian, Triassic and Carboniferous. The rock in the study area’s mainly for fuchsia, purple gray, pale yellow sandstone, shale and siltstone, shale, feldspar quartz sandstone. According to the field survey shows that excavated slopes in the study area’s mainly for interbedded formations. The exist of interbedded phenomena effectively accelerated weathering differences in the study area of the slope, brought trouble for slope protection.Study area is located in rainforest region of southwest Yunnan, which is hot and rainy all year round. According to the laboratory experiment shows that red bed is the rock with weatherproof ability and easy expansion hydrolysis. According to the direct shear tests shows that the shear strength of the red bed significantly reduce, mainly in the change of the C、φ (p Value, the value significantly reduce. According to the hydrolysis test shows that the weathered and disintegration speed of the red bed significantly faster under the condition of wet and dry cycling. Rainforest environment of southwest Yunnan forming a wet-dry cycle system in the natural environment, under the influence of this special environment, the weathering rate of red bed significantly faster in study area.The main types of disasters is landslides and the collapse in the study area, there is not landslides and other disasters. According to the analyzing and summarizing to the slope instability failure modes of study area, the main instability and failure mechanisms of highway slope can be summed up as follows:Landslide divided l,The wedge landslides; 2, Bedding landslide; 3, Nearly horizontal landslide; 4, Fault Zone formation landslide; 5, Strongly weathered layer landslide; 6, landslide of subgrade fill and spoil. Collapse divided 1, Dump-style collapse; 2, Slip type collapse; 3, The wrong split type collapse; 4, Crack style collapse.By analyzing the influence of the special environment to highway slope in the study area, againsting failure mechanism of different types slope, provide effective protective measures. Because of the hot and wet tropical rainforest environment conditions, the main protection methods for slope protection as follows:Prestressed cable with sash beams for protection, inside and outside drainage measures of the highway slope. This protection method is particularly appropriate for the abundant rainfall ares, which can effectively reinforce the slope and better to avoid water blocking phenomenon form heavy rains.