小应变原岩状态下应力路径旋转对剪切模量的影响

Effect of stress path circumgyration on shear modulus under small strain and initial stress state

以重塑土经K 0固结形成的试样为试验对象,采用英国GDS公司生产的STDTTS+UNSAT(7 kN/1700 kPa)型号高级应力路径三轴测试系统,研究了在小应变范围内应力路径旋转对土体剪切模量的影响以及剪切模量随应变变化的趋势。研究表明,在小应变范围内,剪切模量的初始值随试验应力路径与近期应力历史间的夹角θ的增大而增大,当两者完全相反时,应力路径旋转对土体在小应变条件下的剪切模量影响最大;完全一致时,其影响最弱。而且,在小应变范围内,割线剪切模量总是大于切线剪切模量;当剪切应变采用对数坐标表示时,剪切模量随着剪切应变的增加而衰减,且衰减的规律都可以表示为带有两个拐点的反S型曲线,经分析验证本文所得公式3可以对此特性进行很好地反映;但应力路径、应变范围不同其衰减幅度不同。

The test object was remolded soil after K 0 consolidation.Using advanced stress path triaxial system,STDTTS＋UNSAT（7 kN/1700 kPa） produced by GDS of UK,the effect of stress path circumgyration on shear modulus and the trend of shear modulus along with variation of shear strain under small strain were studied.Some conclusions were drawn.Under the condition of small strain,the initial value of shear modulus increased along with the increment of angle θ between trail stress paths and recent stress history.If the two directions were entirely reverse,the effect of stress path circumgyration on shear modulus was the largest;if they coincided completely,the effect was very feeble.At the same time,under the condition of small strain,firstly,the secant shear modulus was always larger than the tangent shear modulus.Secondly,when the logarithmic coordinates were applied to describe shear strain,the decrease of shear modulus with shear strain could be expressed by reversed S shape curve with two inflexion points,and through analyzing and validating,the deduced equation could perfectly reflect this characteristic.Finally,different stress paths and strain areas would lead to different attenuation trends.