Experimental Study On Engineering Characteristics Of Inclined-straight Piles Composite Structure With Different Pile Spacing At The Foot Of Embankment Slope

The inclined-straight piles composite structure is a new type of pile-body reinforced embankment,the pile spacing,inclined pile,pile length and so on have direct influence on its engineering characteristics.The results show that:When loading,the peak of the horizontal displacement of the pile body of the inclined pile is at the top of the pile,the horizontal displacement of the pile body is reduced with the increase of the depth,the horizontal displacement of the middle part is slightly increased,the horizontal displacement of the pile body is greater than the growth rate of the lower part of the pile body,the horizontal displacement of the pile bottom is the smallest,the instability mode of the inclined-straight pile combined structure is shown as a "translation+rotation around the bottom of the pile",the front side of the straight pile and the back surface of the inclined pile is in tension,the front side of the straight pile and the back surface strain peak are in the middle part of the pile body.The peak of the front and back strain of the inclined pile is on the body part of the pile;the peak of the bending moment of the straight pile is at the middle part of the pile body and the bending moment of the inclined pile the value is on the pile body part,the bending moment of the straight pile and the inclined pile body is increased as the distance is increased,and the bending moment of each inclined-straight pile composite structure is mainly influenced by the pulling force,and the peak position of the axial force of the straight pile is mostly found in the middle part of the pile body,and the axial force peak value of the pile body of the inclined pile is mostly found on the pile body part.The peak of the front soil pressure of the straight pile is in the middle of the pile body,and the peak of the front soil pressure of the inclined pile is in the upper part of the pile body.With the increase of the distance,the pressure of the front soil of the front straight pile and the rear inclined pile is increased with the distance.(2)At the time of unloading,the horizontal displacement,strain,bending moment,axial force and front earth pressure curve of the inclined pile of each inclined-straight piles composite structure are similar to that of the loading,and with the decrease of the load,the horizontal displacement,strain,bending moment,axial force of the inclined pile and the pressure of the front soil of the pile have corresponding rebound,However,when unloading to 0,the pile body still has horizontal displacement,strain,axial force and bending moment,and the stress exists in the soil when it is unloaded to 0.(3)The strength design of the upper part of the inclined pile shall be strengthened in the structure design of the inclined-straight piles composite structure to strengthen the anti-horizontal displacement capability of the pile,and the horizontal displacement monitoring of the upper position of the inclined pile shall be strengthened in the actual project.The dangerous failure point of the pile body of the straight pile is at the middle part of the pile body,and the dangerous failure point of the pile body of the inclined pile is on the pile body part.In the structure design of the inclined-straight pile combination,the quality control of the middle part of the straight pile and the upper part of the inclined pile shall be strengthened.The failure mode of the inclined-straight piles composite structure is bending failure,and the straight pile is damaged prior to the inclined pile.In the structure design of the inclined-straight pile combination,the rigidity of the front straight pile can be enhanced to improve the failure load of the front straight pile,and when the front row of the inclined-straight piles composite structure is straight.When the pile,the soil arch between the piles and the inclined pile reach the ultimate load at the same time,it is the optimal working state of the inclined-straight piles composite structure(4)The inclined-straight piles composite structure with 3D pile spacing has the best horizontal displacement resistance,the best bending resistance and the smallest earth pressure in front of the pile.It is suggested that the pile spacing should be set to 3D in practical engineering.