循环荷载下红层泥岩土的动态特性

针对红层泥岩土这种特殊的粒类材料,通过动三轴试验研究了其在循环荷载下的动态特性。分析了应变和围压对动态参数(动模量、阻尼比)的影响,在对动模量归一化的基础上,并考虑最大阻尼比与围压的关系,提出了一个阻尼比的计算方法。引入了动应力水平的概念,由试验数据得到红层泥岩土的临界动应力水平为30%左右。动强度随围压增加而增大,而随振次的增加减小;在较小的破坏应变标准下,动应力对动强度的影响起主导作用,破坏应变标准增大时,振次的影响起主要作用。根据累积应变曲线的发展趋势,把红层泥岩土的累积变形分为稳定型和破坏型,分析了产生不同变形曲线的原因,并分别采用不同的经验公式对两种累积变形进行计算,得到了各参数的取值范围。

Dynamic characteristics of red-mudstone soils under cyclic loads

The dynamic characteristics of red-mudstone(as a special grain material) under cyclic loads are studied through cyclic triaxial tests.The effects of strain and confining pressure on the dynamic parameters(dynamic modulus and damping ratio) are analyzed.Based on the normalization of dynamic modulus and considering the relationship between the maximum damping ratio and confining pressure,this paper proposes a method for calculating the damping ratio.After introducing the concept of dynamic stress level,we acquire that the critical level of dynamic stress is about 30%.The dynamic intensity increases with the increasing confining pressure,and decreases with the development of the number of cyclic loads applications.Stress is a leading role on the dynamic intensity in the smaller strain failure standard,moreover,the number of cyclic loads applications plays a major role in the increase in strain failure standard.According to the trend features of the strain curve,accumulative deformation of red-mudstone can be divided into two types: stable and failure forms,and the mechanisms causing the two types are explained.Two different empirical formulas are employed to calculate the corresponding accumulative deformation,meanwhile,we acquire the range of each formula parameter related to the samples used in this test.