Study On The Proportion Of Backfill-grouting Materials And Grout Deformation Properties Of Shield Tunnel

With the wide use of Shield tunneling method in important substructure works in our country, it has become a major method applied in city subway construction. During the construction with shield machine, backfill grouting is a necessary and key procedure, which can actively control stratum displacement and ground-stress release by filling the shield tail void, and thus reduce surround soil displacement and surface settlement. Current studies, however, focus mainly on the numerical simulation of backfill grouting and the deciding of parameters excessively relied on construction experience and statistical data, therefore it is still unclear about the deformation law of hardening grout under grouting pressure. This paper aimes for the fine sand medium during the construction of YellowRivercrossing tunnel with shield tunneling method, a series of grouting material optimal mixing proportion tests were carried out. With the developed grout shrinking test apparatus and large scale grouting pressure dissipation test appratus, the grout deformation properties under pressure were studied. The main works of this paper are as follow:(1) Aiming at the fine sand medium of YellowRivercrossing tunnel, uniform experimental method was applied in the optimal formula of grouting material, it makes basis for engineering suitable slurry preparation. The influences of grouting material additives on slurry properties were also analyzed. Test results show the content of bentonite and water reducing agent has significant influence on slurry properties.(2) Developed a set of grout shrinking test apparatus and use it systemly studied the grout deformation law after grouting. Discussed the influence of grouting pressure and grouting material on grout deformation. Based on the tests a mathematical model was proposed to simulate the deformation of grout.(3) Developed a large scale grouting pressure dissipation test apparatus and use it studied the grouting pressure dissipation properties. The grouting pressure dissipation law of surrounded each with clay and sand was comparatively analyzed. The test results fit well with the results calculated with the proposed grout deformation mathematical model, which confirmed the reliability of this model.