Study On The Effects Of Soil Liquefaction Induced Lateral Spreading On Pile Foundation

Much attention has been paid to the severe damages caused byearthquake, and then extensive researches have been carried out onfailure mechanism, soil dynamic characteristic, saturated sandliquefaction. For its proper accommodation to various deposit and loadcondition, characterized as large bearing capacity, high stability, lowsedimentation, reinforced concrete piles have been widely used in thedeep foundation of high building, heavy-loaded workshop, bridge, wharf,etc. With the rapid development of our national economy, studies on theeffect of liquefaction-induced lateral spreading on pile foundation willnaturally make it become an important research aspect in the fields ofpresent geotechnical engineering.By means of collecting previous information, theoretical analyzing,computer modeling, a summary was made on the research status ofliquefaction induced lateral spreading. Based on the fact that single pileor pile group's response to lateral spreading mainly depends on its owncharacteristics, soil's liquefied characteristics, soil-pile interaction, soil'sdeflection mode, systemic researches were carried out on soil'sliquefaction and undrained characteristics, mechanics analysis mode onpile deflection, pile's bending performance, single pile and pile group'sresponse to lateral spreading. Some useful conclusions were reached afterthat.Using nonlinear rotational spring to model pile material's nonlinearbending response, spring slider element to model nonlinear interactionbetween soil and pile, including superficial fraction and lateral pressure, amodel was established to evaluate the strain and stress caused byhorizontal displacement.Related experiments show that sand will exhibit its softeningcharacteristics under the monotonic load and cyclic load by liquefactionor limit liquefaction. Different properties will be obtained for liquefiedsoil under cyclic load and static load. Volume change due to thereconsolidation of liquefied soil will mainly depend on the structuraldamage degree, most was completed when effective stress is approaching zero.By analyzing concrete and steel mechanics, reinforced concreteaseismatic properties, a model was established to simulate reinforcedconcrete pile and prestressed pile's bending capacity and deflection. Andthen lateral load's characteristics acting on the pile failure mechanismwere specified.By analyzing the effect of pile's material, diameter, axial load,magnitude of soil displacement, relative stiffness of soil-pile, the failuremechanism and response of pile to lateral force acting on the pile wereillustrated, the maximum soil displacement required to caused pile failurewas quantified. Under the given axial load, characteristic length of soilpile system, depth of liquefiable layer, pile's damaged shape can bemodeled with the established model. The proper reflection of modelingresult to pile's actual failure condition proved that the carried analysis,related assumption and the chosen model are correct.Primary study were carried out on the pile group's response toliquefaction induced lateral spreading. Upon a simplified assumption, amodel was established, mainly to explain the effect of shear stiffness ofsoil, which lies within the piles, on pile group. Analysis were also carriedout on the effect of pile group's cap connection. Results from analyzing 2×2, 3×3, 4×4 pile group indicate that stiffness of soil plays a veryimportant role when the pile group are subjected to the lateral spreading,its magnitude will affect the formation of soil flow condition.