基于离散元的钢‑土界面往复剪切特性研究∗

Reciprocating Shear Characteristics of Steel-soil Interface Based on Discrete Element Method

摘要:

架空直立式码头结构被越来越多的应用于现代化内河港口建设，码头中所使用的大直径钢护筒嵌岩桩与桩周回填土形成钢?土界面，在船舶系靠等重复荷载作用下，界面的往复剪切行为影响桩基的承载性能。使用颗粒流软件及离散元方法，通过改变接触面的运动方式模拟了钢?土界面往复剪切特性，研究了接触面类型、剪切频率和剪切振幅等对往复剪切特性和界面能量变化的影响。研究结果表明：试样的剪切区域面积、剪切应力分布受接触面类型及粗糙度影响较大；同种类型的接触面，法向应力越大剪切区域面积会随之增大，但剪切区域面积的增加存在上限；剪切应力的主要作用范围在接触面中部，作用范围随着法向应力的增大而增大，剪切效果是几种因素共同作用的结果；在往复剪切运动中，各界面接触面附近孔隙率随时间步长增大不断减小，部分接触面孔隙率呈周期性波动；剪切频率、振幅对接触面附近孔隙率影响不大；边界能中大部分转化为应变能，小部分转化为摩擦能并受界面类型、界面粗糙度等因素的影响。

Abstract:

The structure of overhead vertical wharf is increasingly used in the construction of modern inland ports. The large-diameter steel casing rock socketed pile used in the wharf and the backfill around the pile form a STEEL-SOIL interface. Under the action of repeated loads such as ship berthing， the reciprocating shear behavior of the interface affects the bearing capacity of the pile foundation. Using particle flow software and the discrete element method， the reciprocating shear characteristics of the steel-soil interface are simulated by changing the movement modes of the contact surface. The effects of contact surface type， shear frequency and shear amplitude on the reciprocating shear characteristics and the change of interface energy are studied. The results show that the shear area and shear stress distribution of the specimen are greatly affected by the type and roughness of the contact surface； for the same type of contact surface， the larger the normal stress is， the larger the shear area will be， but there is an upper limit to the increase in the shear area； the main active area of the shear stress is in the middle of the contact surface， and it increases with the increase of the normal stress； the shear effect is the result of several factors； in the reciprocating shear movement， the porosity near each interface decreases with the increase of time step， and the porosity near some interfaces fluctuates periodically； the shear frequency and amplitude have little influence on the porosity near the interface； most of the boundary energy is transformed into strain energy， and a small part is converted into friction energy； the transformation is affected by the interface type， interface roughness and other factors.