Experimental analyses of high-filled cut-and-cover tunnel for reduction of the earth pressure

The pressure distribution over buried structures like pipes and tunnels are considered a main factor in the economic design of such structures. This study shows the effect of using crumb rubber mixed with sand and geogrid layers to enhance the soil pressure distribution over that buried structure. That method is titled a high-filled cut-and-cover (HFCCT) construction method. Crumb rubber particles pieces mixed with sand as a lightweight fill material (LFM) in HFCCT are used to reduce the vertical earth pressure (VEP) on that buried tunnel. Geogrid reinforcement layer above the HFCCT system to strengthen the soil layers above the tunnels were implemental. A physical model is built to simulate such conditions by applying external loads to the treated soil layers above the tunnel. The strains are measured on the external body of the tunnel, while the soil pressure is assessed through pressure gauges around the tunnel. The results obtained from the crumb rubber models are compared with those obtained from the geogrid model. It was deduced that using crumb rubber and geogrid, reduces the earth pressure above the cut-and-cover tunnel (CCT). As compared to the use of geogrid, the utilization of rubber as a substitute for soil results in a 27% drop in pressure. The obtained results show that the use of geogrids in sandy soils leads to uniform stress, while using rubber sand could reduce the maximum stress of the soil above the tunnel.