NUMERICAL ANALYSES OF HIGH-FILLED CUT-AND-COVER TUNNEL USING PLAXIS 3D

Civil Engineering

Huge fill soil in high-fill cut-and-cover tunnels (HFCCT) generates high pressure above the tunnel, while rubber soil serves as an effective lightweight fill material to reduce weight. The main factor affecting the stability of the cut-and-cover (CCT) is reducing the load and settlement on the CCT. This paper employs finite element software, PLAXIS 3D, to conduct a numerical analysis of the HFCCT model, which includes a replacement part of sand soil and a rubber-sand mixture. Both data sets are simultaneously gathered in a direct shear test and a relative density test. Data are analyzed in the context of mixture theory and with the aid of numerical simulations. The Mohr Coulomb model uses rubber sand, and the Hardening Soil model uses sand. A numerical model is built to simulate such conditions for filling sand above (CCT) to the rubber-sand layer above the tunnel. And, using a concrete model to simulate the lining of CCT, the performance of rubber sand is measured, while the soil layer increases through the numerical results. The effect of rubber on vertical earth pressure (VEP) on CCT is compared with the varying thickness of the rubber-sand layer to obtain the best economic thickness. This study also considers the impact of settlement on CCT. The PLAXIS output shows the layer mechanism and the minimum earth pressure in VEP that will be reached when using rubber-sand. The utilization of rubber as a substitute for soil results in a uniform load reduction mechanism and increases the bearing capacity of sand.

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