Key Technology Of Railway Tunnel Construction Under The Condition Of Cracked Basalt And Clotted Limestone Surrounding Rock

Yunnan region of China, located at the edges of both Eurasian plate and Indian plate, is complex in geologic structure and terrain. The geologic structure is changeable and the active fracture is well developed. Besides, the neo-tectonic movement is really strong. Influenced by the folding, faulting as well as magma intrusion activities, the strata are obviously cut and the textual jointing is well developed and the mechanical properties of strata are relatively poor while some partial sections of these strata are particularly crumbling. The properties of rock are complex and changeable, especially for the volcanic formed by several multiple phase eruptions and the dike formed by multiple phase intrusive activities. Their variation is irregular. Moreover, the mechanical properties of the contact zone between basalt and tufa are relatively poor. Surface water is extremely easy to percolates down along the faults and fissures and then softens the soft rock and erodes the small particles and thus reduces the mechanical properties. As the railways construction in Yunnan region develops massively, the geology containing basalt and tufa has brought great security risks to the constructions of railway tunnels. Therefore, research on the key techniques of the constructions of tunnels built in the strata containing basalt and tufa is very necessary.This paper is based on the construction of Heluoshan tunnel in Dali railway. It is a research about railway tunnel comprehensive advance geological forecasting techniques、 fragmentation basalt drilling-blasting techniques、tunnel mechanization technology、disaster monitoring and early warning and security of protection technology. Aiming at the featrue of the combination basalt with tuff, comprehensive advanced geological forecasting techniques can be proposed to insure the excavation safety. Direct at small cross-section tunnel to do the research about drilling-blasting operation and tunnel mechanization technology in order to improve the efficiency of construction. Through the research of measurements and reinforcement technology on the surrounding rock, the secondary tunnel lining and operation safety will be ensured, and in the same time the experience of deformation observation will be accumulated.On the basis of regional geology, hydrological engineering geology, seismic geology, meteorology, hydrology, etc., selecting ejection characteristics of basalt, tuff distribution and characteristic of width change as research objects, physical and mechanical characteristics of basalt and tuff are mainly studied, and stability of tunnel cavern with basalt and tuff is evaluated in this paper. Corresponding optimization measures are put forward, and tunnel construction technology with basalt clamp tuff and technology method system of safety protection are summarized. This paper has some degree of guiding significance in publicizing technology experience and guiding construction of similar projects.