| The Keku bridge dangerous rock in Wenchuan to Maerkang expressway is located on the high and steep slope of the left line of Keku bridge.The slope surface looks like sawtooth because of the early caving.Apart from the rock mass,the structural cracks and unloading cracks in the slope are developed.The stability of the dangerous rock area is poor,and many dangerous rock bodies are broken off from the parent rock,which seriously affects the safety and progress of the construction of the Wenma expressway.On the basis of geological conditions such as topography,lithology,geological structure and groundwater,the position,scale and possible instability mode of the dangerous rock development are fully identified.The stability calculation based on the rigid body limit equilibrium theory is carried out for different dangerous rocks and the movement of each stage after the possible collapse of the dangerous rock is special.Finally,some pertinent engineering measures are proposed.The main contents are as follows:(1)According to field investigation data,the whole dangerous rock area can be divided into five dangerous rock zones and some dangerous rock masses,and their respective sizes are expounded according to their spatial distribution.The control factors affecting the development of the dangerous rock are analyzed.The internal factors are mainly topographic landforms,slope structures and stratigraphic lithology,and the external factors mainly include rainfall,earthquake,weathering and human activities.(2)The failure mode of the dangerous rock is mainly falling,and the failure mechanism of the WYT3-1 in the dangerous rock in the study area is analyzed by the discrete element program(UDEC).The result shows that the lower part of the rock is near to the air,and the rock mass is mainly controlled by the two groups of controlled collapse structures,and the rock mass is gradually extended to a certain degree when the gentle slope of the rock mass is gradually extended to a certain extent.The slip deformation of the main structural plane outside the slope falls down,which is a typical fall failure.(3)By using the rigid limit equilibrium method in the static analysis method,the stability of the dangerous rock in the study area under two load combinations(natural state and earthquake state)is calculated,and the quantitative calculation results of the stability of each dangerous rock under different load combinations are obtained,which shows that most of them are in under stable state.(4)The empirical formula calculation and numerical simulation based on ROCFALL software are used to analyze the kinematic characteristics of rockfall in the dangerous rock zone of the Keku bridge,which may have great harm to the construction of the project.(5)According to the harmfulness of rockfall and rockfall in the study area,a scientific and reasonable prevention and control scheme is put forward.The scheme is as follows: take the passive protection measures to the WYD1 of the dangerous rock zone,and take the active protective measures of the dangerous rock zone WYD2 and WYD3,and adopt the " clearance+ active network" to protect the dangerous rock zone WYD4 and WYD5. |
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