Experimental Study And Application Of Physical And Mechanical Properties Of Gypsum-containing Marl In Dugongling Tunnel

The Dugongling Tunnel traverses a marl formation containing irregularly developed gypsum and anhydrite rocks.The formation softens and expands when it encounters water,causing lining cracks in the tunnel,partial cracking of the second liner,uplift of the road surface,and deformation of overhaul road.In order to ensure the scientific,rational and effective development of the tunnel disease treatment program.this paper studies the physical and mechanical properties of the gypsum-containing marl in the Dugongling tunnel.This paper takes the gypsum-mudstone of Dugongling tunnel as the research object,tests the expansion mechanical properties,uniaxial compression and other related physical and mechanical properties under different water-immersion time conditions,and obtains the following conclusions:1)Gypsum marl composition test.Through the X-ray diffraction analysis of the marl powder after grinding,it was found that the mineral composition was mainly gypsum 90%,quartz 2%,anhydrite 5%,and dolomite 2%.2)Free expansion rate.The expansion rate test was performed using a free dilatometer.The axial free expansion rate was 1.68%to 2.57%,the radial free expansion rate was 0.52%to0.83%,and the axial free expansion rate was a radial free expansion rate of 3.1 to 3.5 Times.3)Side limit expansion force.The maximum expansion force test was performed using the equilibrium pressurization method.The ultimate expansion force of the test piece was2.271 to 2.892 MPa.4)Uniaxial compressive strength.The uniaxial compressive strength of the specimen under different water immersion times was measured,and the relation between compressive strength and water absorption was found to be a quadratic function(y=0.103x~2-1.927x+17.84),and the compressive strength was related to the water absorption rate.Increase gradually and then gradually increase.5)Elastic modulus and Poisson's ratio.Measure the elastic modulus and Poisson's ratio of the specimen under different water immersion times,and obtain the relationship between the elastic modulus and the water absorption rate as a quadratic function(y=0.14x^2-0.188x+1.287),the elastic modulus with the water absorption rate The increase of Poisson's ratio gradually decreases and then gradually increases;the Poisson's ratio of the specimen remains basically unchanged with the increase of water absorption;6)Sulfate ion concentration.The sulfate ion concentration of the anhydrite rock under different immersion time was tested.The final ion concentration reached 742mg/L~758mg/L,belonging to weak corrosion.Based on the above experimental results,the design parameters of reinforcement treatment were calculated by the load structure method.It was verified that the safety factors and crack widths of the key parts of the lining meet the specification standards,indicating the safety of the design parameters of the disease treatment plan.