Experimental Study on the Mechanical Characteristics of Piled Rafts Under Vertical-Horizontal Combined Loads

To study mechanical characteristics of piled raft under vertical-horizontal combined loads, several indoor model tests were conducted, considering the influence of length to diameter ratios, pile numbers, vertical loads and pile spacing, and the changes of the bending moment and shear forces in pile shafts and earth pressure on piles were analyzed. The test results showed that: The horizontal bearing capacity of piled rafts increased with the increase of vertical loads, pile numbers, length and spacing of piles, on the contrary, the horizontal displacement of piled rafts decreased with their increase. The maximum bending moment was located at 0.3 times length of piles below the earth’s surface,and the maximum bending moment in the front piles was larger than that in the rear,which was about 1.14 times bending moment in the rear piles. The bending moment and shear forces decreased with the increase of vertical loads,and the maximum bending moment of piles increased with the decrease of pile spacing but the bending moment at tops and tips of piles almost kept stable. The location of the maximum negative shear forces could be controlled by adjusting the pile spacing, and the shear forces at the tops of piles decreased with the increase of pile spacing but the shear forces at the tips changed conversely. To increase the pile spacing could mobilize a wider range soil between piles,however the internal forces in piles almost kept steady. The failure mode of piled raftes conformed to the failure laws of rigid piles under the combined loads. The ultimate horizontal bearing capacity of piles was mainly controlled by the compressive strength of soil around piles.