Abstract: Using a typical four-lane highway tunnel as a prototype, we conducted static pushover tests on a scaled-down model to examine the variations in ground displacement, ground pressure, and ground cracking with pushover distance. Compared with the test results of two-lane tunnel, the test results indicate that the ground is displaced reversely from the arching line and then cracked. Therefore, the location of fracture point should be modified from the bottom of the side wall to the arching line. The test results also show that the ground slides smoothly along the tunnel circumferential direction with a large inclination angle, so the potential slip planes should be modified from constant vertical to linear inclination. According to these test results, the applicability of surrounding ground pressure calculation model assumption in the four-lane tunnel is discussed, and a modified ground pressure calculation model suitable for the four-lane highway tunnels is proposed. These researches can provide experimental basis and technical support for the seismic calculation/checking of the four-lane highway tunnel, and provide reference for further improvement of surrounding ground pressure calculation model.

Key words: four-lane highway tunnel, downscale model test, static pushover test, ground pressure, modified calculation model