Study Of Double Support And Double Lining Of Tunnel

With the improvement of our railway network and construction standards, especiallythe large number of high-speed rail and passenger railway construction, the tunnelconstruction scale and technical level also embarked on a new level. But also facingchallenges of complex environment and poor geological construction safety problems,including Deformation of weak rock tunnel construction control technology upgrade is veryurgent. Lan Yu line of Lan Guang segments is in the northeastern margin of the TibetanPlateau complex special geological tectonic environment, especially Strong tectoniccompression. Geological structure is very complex, the stress state is a high-very high.Affected by multiphase deformation and extremely low metamorphism and transformationof high ground stress and tectonic fault of groundwater and other factors, the formation oflarge deformation of soft rock, hard rock brittle collapse and massive flow of sand, etc. is aspecial geological problems in specific environment. This is rare at home and abroad.Focusing on the construction difficulties such as crossing softcarbonaceous rock,difficult design and construction conditions, deform unstablilities of initial linging, crackscaused by fast supporting and lining construction during the construction of LiangshuiTunnel of Lanzhou-Chongqing Railway, the researches on double-layer supporting anddouble-layer lining have been implemented respectively. On the basis of designparameters and construction parameters,through researchs on deform of initial supporting,surrounding rock pressure, contact stress, steel frame stress, rebar stress and concrete stressof pilot section, and through the stress-deform analysis of double-layer supporting anddouble-layer lining, the stress condiction and deform regularities of supporting and liningstructure have been mastered. The main researching resultants are as follows.1. Fordouble-layer supporting structure,(1) the supporting capicities of supporting structureincreases promptly and the deform velocity decreases slightly. The deform velocity aftersecond layer supporting decreases rapidly. The required deform velocity limit can beensured before the construction of second layer lining.(2). for the construction ofdouble-layer supporting. only one set lining platform is adopted. The first supporting can becontructed stage by stage, the second layer supporting can be constructed by using of water-proof engineering platform before the construction of invert engineering.allconstrctions can be implemented parallelly. The construction process is not influented andthe construction safety factor is improved.2. for double-layer lining,(1) the bearingcapacity of lining structure increases rapidly. The first layer lining can control the deformvelocity in that the first lining is not limited with deform velovity. The second layer lining isconstructed after the stabilization of lining structure with a higher safety factor. Theconstruction of second lining acts an active effect to the safety during the operation period.(2) The construction costs increase rapidly. Two sets of linging platforms are required andthe platform is assembled within tunnel. Other construction processs are hindered and someprocesses may be stopped. The construction process is decreased rapidly.