Research On Leakage Mechanism And Water Stopping Technology Of Frozen Hole In Tunnel

Based on the study of the bond between the old and new concrete interface,combined with Zeiss electronic scanning electron microscope and fracturing test,this paper explores the causes of the formation of the traditional freezing hole plugging materials and the water seepage channel of the freezing hole wall,and then from the perspective of the leakage mechanism,puts forward three different leakage plugging formulas,and carries out relevant material performance tests,simulation leakage tests,etc.to verify the feasibility of the scheme.Finally,the successful treatment scheme was popularized and the industrial test was carried out on the spot.The main research contents and achievements of this paper are as follows:(1)When the traditional plugging materials block the freezing holes of cement segments,because of the difference of physical properties of materials,the complex construction environment on site,the alternation of cold and heat of freezing hole walls and the interference of impurities and other reasons,the structural defects such as voids,pores and micro cracks at the interface are enriched to form a through water seepage channel.The laboratory uses the micro electron microscope to scanIt is found that there are obvious pores and uniform cracks at the interface,and the crack width is 0.45-3.2 μ M.(2)Experiments were carried out to prepare modified cement mortar materials in cement mortar by mixing HCSA expansive agent and epoxy resin emulsion,and the related basic performance tests were carried out.The test results showed that the addition of two additives had remarkable effect on reducing material shrinkage and improving the impermeability of materials.(3)In the experiment,two-component rigid Epoxy Mastic was selected as a new plugging material and interface agent.Compared with traditional plugging materials,rigid Epoxy Mastic has excellent adhesion and environmental adaptability.The bonding force between the solidified material and the concrete material can reach 3-4mpa,and its flexible material can repair the structural defects of the concrete at the interface,making the interface structure more perfect.(4)The laboratory carried out the simulated leakage test,using the traditional plugging materials,modified cement mortar materials,rigid epoxy mortar and rigid epoxy mortar(interface agent)+ traditional plugging materials to simulate the sealing of frozen holes,and installed a hydrostatic pressure device on the back of the test block to apply a hydrostatic pressure of 0.33-0.36 mpa,observed the water seepage of each group,and results the traditional plugging materialsThe test group and the new plugging formula test group had water leakage at 0.5h and 3.5H after the test respectively,while the test group with rigid Epoxy Mastic and the test group as the interface agent had no water leakage for 3 months.(5)The results show that the whole section plugging test group of rigid Epoxy Mastic fails to achieve the expected effect due to the treatment of freezing hole wall and the limitation of workers’ operation level,while the test group of rigid Epoxy Mastic(interface agent)+ traditional plugging materials still obtains the similar test results with the laboratoryWhen it is used as interface agent,it can save 87.5 %construction cost and has better economic benefits.