Model tests on resistance behaviors of rock-concrete interface of rock-sockted piles in red-sandstone rock

Model tests on the shear resistance behaviors of rock-concrete interface are carried out with regard to rock-socketed piles in red-sandstone rock. The results indicate that the shear resistance of rock-socketed piles in red-sandstone decreases with increase of depth, and fluctuates along with characters of rock joints and cracks and the drilling quality and so on. In addition, the mobilized pile resistance in the upper zone is much greater than that in the lower zone while the load comes to the limit vertical bearing capacity of the piles. The length of the piles will impact load transfer efficiency and its speed of shear resistance obviously, and the efficiency will decrease and the ultimate resistance will minish with the increase of the pile length. Also, the distribution of shear resistance will be affected by rock state. With the softening of the red-sandstone rock around the pile intenerating, both the ultimate resistance value and the bearing capacity reduce. With rigidity of red-sandstone rock under the piles, the proportion of resistance declines and the resistance exerts faster. The increase of length and rigidity of the red-sandstone rock will make the distribution of resistance concentrate in the upper zone. It is concluded that the bearing capacity is much safer according to the present code.