Study On Dynamic Response Characteristics Of H-Type Composite Anti-Slide Pile Reinforced Slope

Up to now,to promote the economic development of the southwest region and maintain the safety of people’s lives and property,China has made remarkable achievements in the fields of traffic engineering,slope engineering and disaster prevention.However,there are many mountainous areas in Southwest China with complex and changeable geological conditions and frequent earthquakes.The problem of landslide disasters caused by earthquakes is still prominent,which poses a serious threat to local economic development.Therefore,it is urgent to consider the prevention and control of landslide disasters from the perspective of dynamics.To research the dynamic response of h-type composite anti-slide pile and slope under earthquake,this paper firstly carried out two groups of shaking table model tests on the slope without anti-slide pile reinforcement and the slope reinforced by h-type composite anti-slide pile based on a slope treatment project in ZK142+124～ZK142+274 section of Jiumian Expressway.The difference of dynamic response and seismic damage location of the slope before and after reinforcement was obtained.At the same time,the acceleration,dynamic earth pressure and internal force of h-type composite anti-slide pile were analyzed.Then,based on the numerical simulation,the results of the model test are verified,and the sensitivity analysis of the structural design parameters of the h-type composite anti-slide pile is carried out,and a series of parameters conducive to improving the seismic retaining performance of the h-type composite anti-slide pile are obtained.The results of this paper can provide some reference for the seismic design of h-type composite anti-slide pile.The main conclusions are as follows:（1）The h-type combined anti-slide pile can effectively enhance the stability of the slope under earthquake.The test slope without pile has obvious damage when met 0.15g El Centro wave,and it is completely unstable when met 0.40g El Centro wave.The h-type combined anti-slide pile can weaken the amplification effect and surface effect of seismic wave on the slope,and make the slope failure change from disorder and sudden to continuous and cumulative.（2）The cantilever end of the h-type composite anti-slide pile has the strongest response to the seismic wave.The El Centro wave of 13.34Hz～16.18Hz in the low frequency band has a continuous and integral influence on the h-type composite anti-slide pile,which should be paid attention to in the seismic design.The cantilever end of the h-type composite anti-slide pile is conducive to energy dissipation due to the whiplash effect;although the Hilbert energy of the short pile is small,the low frequency component of the Hilbert spectrum of the short pile is more abundant,which makes it easy to accumulate energy.In addition,there are rigid joints at both ends of the pile beam,which makes it easy to cause damage to the short pile joints due to stress concentration.This is consistent with the results of seismic damage analysis and dynamic earth pressure response analysis of the Hilbert marginal spectrum of the pile.（3）When the h-type composite anti-slide pile encounters a relatively low-intensity earthquake,the back side of the long pile shares more than 70%of the dynamic earth pressure.With the upgrading of seismic intensity,the dynamic earth pressure sharing ratio of long and short piles is about 50%.The peak distribution of dynamic earth pressure on the back side of long pile is’anti-S’type,which is mainly manifested in the sharp increase of dynamic earth pressure at the beam joint.The distribution form of dynamic soil pressure in front of long pile is’>’type,and there is a sharp increase point of soil pressure peak at half anchorage section.The distribution form of dynamic earth pressure on the back side of short pile is’<’type,and there are mutation points mainly in the pile body below the sliding surface.The bending moment diagram of the long pile is’s-shaped’distribution,and there is an inflection point near the sliding surface.The first bending moment amplitude appears at 1/3～1/2 anchorage section,and the second bending moment amplitude appears near the beam joint.The short pile has inflection points near the sliding surface and 1/3 anchorage section,and the bending moment amplitude appears at the beam joint and 1/2 anchorage section.（4）Combined with numerical simulation,we suggest that the structural parameters of h-type composite anti-slide pile meet the following range:pile row spacing is 4D～6D（D is pile diameter）;the length of cantilever end is l/5～l/3 and the anchor depth of long pile is l/3～l/2（l is the length of long pile）;the anchor depth of short pile is l₁/3～l₁/2（l₁ is the length of short pile）;the relative stiffness of the beam is 1.0EI～2.0EI（EI is the anti-sliding stiffness of the pile）.