DISCRETE ELEMENT ANALYSIS OF EARTH PRESSURE AND INFLUENCING FACTORS FOR HIGH-FILLED CUT- AND -COVER TUNNEL WITH DIFFERENT HEIGHT-SPAN RATIOS BASED ON EPS LOAD REDUCTION

Using the discrete element software called PFC^2D, we simulate the earth pressure variation of arched cut-and-cover tunnel with different height-span ratios(0.4 to 0.9)under the EPS load reduction measures. Moreover, we also analyze the vertical earth pressure and vertical displacement on top of the cut-and-cover tunnel, horizontal earth pressure on sides of the cut-and-cover tunnel and soil particle contact at the micro level. We understand the change of earth pressure in the inner soil. Meanwhile, we analyze the effects of different groove width ratios and slope angles on earth pressure at the optimal height-span ratio. The result shows that the top of arched cut-and-cover tunnel appears soil arch effect when there is EPS load reduction. The vertical earth pressure on top of the cut-and-cover tunnel changes from the center of the model to the sides with a U-shaped distribution. The vertical displacement on top of the cut-and-cover tunnel decreases from the center of the model to the sides with a V-shaped distribution. The horizontal earth pressure on sides of the cut-and-cover tunnel changes with an inclined S-shaped distribution along the vertical direction. At the optimal height-span ratio of 0.8, the soil particle contact shows a good level, where the contact force and coordination number are the smallest, and the porosity is the largest. In addition, with the increase of the groove width ratio, the average vertical earth pressure gradually increases, the vertical displacement difference and the average horizontal earth pressure gradually decrease, and the soil particle contact level becomes worse. With the increase of the slope angle, the average vertical earth pressure gradually decreases, the vertical displacement difference and the average horizontal earth pressure gradually increase, and the soil particle contact level becomes better. The results can provide reference for the selection and construction of high-filled loess cut-and-covert tunnel in the valley area.