Study On Mechanical Properties Of The Existing Tunnel Under The Condition Of Rock With Super Small Thickness

According to the State Council prepared by the national economic and social development of the 13 th five-year plan(draft)by 2020,gross domestic product and per capita income of urban and rural residents by 2010,"Thirteen-Five" period of annual economic growth above 6.5%,strengthen the construction of major infrastructure,high-speed rail mileage of more than 30,000 kilometers,covering 80% of the big cities,new rebuilt the highway traffic mileage of about 30,000 km.With the development of China’s urbanization,traffic congestion has become an acute problem,solve the traffic problems in cities,urban construction of the tunnel is an important means of easing urban traffic congestion.Because of underground space development clearance restrictions,existing buildings and other conditions,more complex interchange of small clips in Rock Tunnel have also appeared,and is gradually increasing.Add rock thickness in the ultra small condition,existing tunnel mechanical characteristics is scarce due to the new tunnel.Based on a large number of documents using three-dimensional numerical simulation software,Midas GTS,cross point,rock and excavation sequence and other variables,of existing tunnel caused by the tunnel to study the mechanical properties,specific contents are as follows:①Based on three dimensional numerical simulation of 32 conditions,comparative analysis of existing tunnel vertical displacement induced by tunnel and ho rizontal displacement fields,research of tunnel displacement fields of law.②Lining based on structural characteristics,determine first principal stressσ1 andσ3 as the third principal stress study on the mechanical properties of lining control index,caused both by comparative analysis of the new tunnel crossing the first main stressσ1 andσ3 changes third principal stress,study of tunnel displacement fields of law.③Based on II times lining masonry structure more for concrete damage,while consider Japan tunnel immediately construction Guide,concrete C25(II times lining masonry used model)tensile strength design value ft=1.27 MPa and compressive strength design value fc=11.9MPa,first proposed to 0.05 times times ft(63.5kPa)and 0.025 times times ft(31.75kPa)as first main stressσ1 divided both tunnel strong effect district,and weak effect district and no effect district of boundaries value;-0.05 times fc(-595kPa)and 0.025 times times fc(-297kPa)σ1 divides an existing tunnel as the third principal stress influence zone and weak influence zone in the affected zone and boundaries.④According to the new tunnel on existing tunnel influence area delineation,ultra small clamping thickness of rock in condition for the first time to determine the effect of tunnel on existing tunnel length,can be used as a future reference of similar design and construction.