According to the analysis, there are five types of deformation failure of the slopes along the road which are shallow freeze-thaw creeping of gravel soil slopes in plateau meadow area, cracking of soft rock high slopes by weathering and freeze-thaw cycling, freeze-thaw slump along the planes of consequent rock slopes, freeze-thaw collapse of big colluvial gravel slopes and freeze-thaw slide along basal rock of residual gravel soil slopes. Grassing, water draining, SNS flexible protection net, concrete insert repair, anchored retaining wall or concrete pier, root pile and anti-sliding pile are selected to treat these deformation failures based on different situation.

1 Introduction

There is about 200 km distance of Xining-Jiuzhi class II road,which connects Qinghai and Sichuan province, is in a typical alpine environment and it passes through five mountains higher than 4000 meters. This complicated-geological-condition road has several high slopes and ancient landslides. There are many deformation failures, collapses and landslides occur every year along this road because of the rebuilding, freeze-thaw cycling and weathering.

2 Environmental Geological Conditions Along This Road
2.1 Climatic conditions

The weather along this road belongs to plateau mountain climate which is dry, cold, windy and hypoxic. The average temperature is 3.4° and the extreme minimum temperature is -36.2° while the day temperature difference is 16°. The amount of precipitation is 400~500mm which concentrates in from July to September.

2.2 Topography and geomorphology

Along this road, there are four geomorphic unitswhich are alpine mountain landscape, alpine mountain basin landscape, alpine deep valley landform and alpine alluvial plain landscape. The altitude of this area is between 3100m and 4000 m. Both south and north sides of this area are higher than the middle which appears like a valley between two mountains. The altitude difference is about 500 m. Most of the alpine deep valleys areV type while U type valleys are rare. There are alluvial flat and first terrace in the bottom of the valleys. Meadows spread over the high terraces and plateau hills.

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