Study On Designing Method Of Prestressed Anchor Cable To Softrock Underground Engineering

It is supportive of weak wall rock of underground project that has always been the technical difficulty of engineering design and the construction. This paper has introduced the surrounding rock loose circle theory and adopted pre-reinforcement techniques. We have done a research on pre-stressed anchor rope in soft rock parameters, structures and construction of underground engineering design by using new-style pre-stressed anchor cable(Adaptive pre-stressed anchor) as the initial support of weak surrounding rock. The main contents of our research are as follows:① The relation between support resistance of surrounding rock and stress variation characteristics —, and between the former one and deformation displacement of underground engineering excavation of soft surrounding rock. After excavation of surrounding rocks of underground engineering, the original rock stress balance has been destructed, and therefore surrounding rock stress should be adjusted. This paper is going to analyze the relationships among plastic displacement, stress variation characteristics of soft rock, development of surrounding rock deformation and active anchoring force according to characteristics of soft rock, underground engineering section size, active principles of anchorage with pre-stressed anchor cable and so on.② Selection of soft rock in underground engineering structure with pre-stressed anchor cable and supporting parameters. A new type of pre-stressed anchor cable(Adaptive pre-stressed anchor) has been used as the primary supporting structure of underground soft rock engineering. Adaptive of pre-stressed anchor cable is designed on the basis of a General pre-stressed anchor cable by installing special adaptive equipment, in order to achieve the aim of reinforcing soft rock deformation of underground engineering, adapting the great wall rock distortion and avoiding deformation caused by overload or failure of pre-stressed anchor cable. The adaptive pre-stressed anchor can automatically adjust the cable tension and deformation according to the resistance of surrounding rock and relationship between supportive and resistant force and displacement. Design of pre-stressed cable anchor support parameters includes anchoring, dip angle, pitch and length of anchor cable and other parameters. As anchoring mechanism varies from different forms of anchor cable, we need to study suitable new-style pre-stressed anchor cable(Adaptive pre-stressed anchor) anchor parameter which are adapt for soft surrounding rock deformation of underground works.③ Studies on techniques of pre-stressed anchor cable for underground engineering in soft rocks construction. Adaptive pre-stressed cables for Pre-stressed anchor rope is adapted for large deformation of surrounding rock support. Adaptive anchor cable construction consists of measurement lofting, hole, fabrication and installation, grouting, anchor tensioning and locking, supplement composed of grouting and bolting processes. Its construction crafts are basically the same as the one of traditional pull-type cable, but partial construction of them differs from each other.④ Analysis of the program of using adaptive design of pre-stressed anchor cable as primary support for large deformation of soft rock tunnel with the example of Xiu Ling crossing of the west line of Pan-Asian railway which from Da Li to Rui Li.