单双向循环荷载作用下砂砾料动模量和阻尼比试验研究

Experimental study on dynamic modulus and damping ratio of sand and gravel under single and double cyclic loads

通过大型振动三轴试验,研究了单双向循环荷载作用下砂砾料动弹性模量和阻尼比的变化规律,分析围压和径向循环动应力对砂砾料动力参数的影响。研究结果表明:在双向振动三轴试验中,砂砾料的轴向动应变受径向动应力的影响较小,动应变主要与施加的轴向动应力大小有关;单双向振动下砂砾料的动弹性模量均随着动应变的增大而逐渐降低,双向振动时砂砾料动弹性模量随动应变的衰减速率基本不变,在相同动应变下双向振动的动模量均低于单向振动;砂砾料在双向振动时的阻尼比大于单向振动,双向振动时消耗的动应变能更大。通过对两种试验条件下的最大动弹性模量、动模量比进行分析,建立了表述单双向试验条件下最大动弹性模量的换算关系式和双向振动试验中动模量比和动应变的修正模型。

The study investigates the dynamic elastic modulus and damping ratio of sand and gravel under single and bidirectional cyclic loads using a large-scale vibration triaxial test.It also analyzes the effects of confining pressure and radial cyclic stress on the dynamic parameters of sand and gravel.The results show that in the bidirectional vibration triaxial test,the axial dynamic strain of sand and gravel is less influenced by the radial dynamic stress,with the dynamic strain primarily related to the applied axial dynam-ic stress.Under both unidirectional and bidirectional vibration,the dynamic elastic modulus of sand and gravel gradually decreases with the increase of dynamic strain.Under bidirectional vibration,the decay rate of dynamic elastic modulus of sand and gravel re-mains essentially unchanged,and the dynamic modulus of bidirectional vibration is lower than that of unidirectional vibration under the same dynamic strain.The damping ratio of sand and gravel under bidirectional vibration is larger than that under unidirectional vibration,and the dynamic strain energy consumed under bidirectional vibration is larger.Based on the analysis of the maximum dy-namic elastic modulus and dynamic modulus ratio under the two test conditions,a conversion relation expressing the maximum dy-namic elastic modulus under single and double direction test conditions and a correction model of the dynamic modulus ratio and dy-namic strain in the bidirectional vibration test were established.The research results can provide a theoretical basis for the seismic design of sand and gravel in high earth-rock dams.