考虑试验阻尼效应的一种土体动力双型抛物线本构模型

A soil dynamic double-parabola constitutive model considering effect of soil test damping

针对土动力试验中土体反向卸载(或加载)曲线形状有时表现为先变化平缓后变化剧烈这一特征,基于土体实验结果的G/Gmax-γ和λ-γ曲线,建立了不规则荷载作用下可调的双型抛物线形式的本构曲线规则,阐述了A型和B型抛物线的函数表达式及实现过程。采用9种方法对试验阻尼比的模拟对比,表明所建立的加卸载准则尤其能准确拟合试验阻尼值,是对广义Masing准则的一种简化及实用化。由于调制因子Ad的可变性,它具有更强地模拟试验本构曲线形状的能力。针对台湾Lotung DHB钻井台阵试验场地,以等效线性化方法SHAKE91、LSSRLI-1,时域非线性方法DESRA-2、Pyke方法、非Masing准则模型1、"隐式应力阻尼等效"模型、"阻尼比退化系数"模型和非Masing准则模型2以及双型抛物线本构模型等9种方法(或模型)分别进行了非线性地震反应分析,并将结果与强震观测记录进行比较,结果表明,双型抛物线本构模型计算的复合加速度地震动的峰值大小、波形大小相对关系及后续波形,与实际地震记录较相一致,说明了模型的合理性以及实际工程应用的可行性。

Firstly,based on the basic characteristic curvesG/ Gmax-γ andλ-γ revealed by the results of the soil dynamic tests,the rules of adjustable double-parabola constitutive curves of reverse unload after load process or reverse load after unload process in irregular load history are established,and function implementation and implement of A type and B type parabola are expounded for the characteristics of reverse load or unload curves sometimes change more flatly at first and then acutely.Secondly,by comparisons of 9 methods simulated results of soil test damping,the load and unload rules of double-parabola model accord with the test results,especially accord with the value of soil test damping,and they can be regarded as the simplification and practicality of generalized Masing rule.Because of the adjustment coefficient Ad can be changed,the model has more powerful capability of simulation the shape of constitutive relationship curves.At last,using the borehole array records of Taiwan Lotung DHB field test,the nonlinear seismic response of DHB site are analyzed by equivalent linear method SHAKE91,LSSRLI-1,nonlinear method in time domain-DESRA-2,Pyke model,Non-Masing rule model ONE,implicit stress damping equivalent model,damping degradation coefficient model,Non-Masing rule model TWO and double-parabola constitutive model respectively.After compared all the synthesizing acceleration ground motions with the observation records,we found the PGA of double-parabola model are almost equal to the observation value,the comparative size relations of waveform,subsequence waveform are agree well with the records.As a result,the rationality of double-parabola constitutive model and the feasibility in practical engineering application are manifested.