Research On The Mechanical Response Characteristics Of PRD Saturated Muck Soil Under Cyclic Loading

With the rapid development of China’s economic construction, geotechnical problems caused by cyclic loading increasingly attracted the attention of scholars in geotechnical engineering. A series of undrained cyclic triaxial tests were performed on the mechanical response characteristics of PRD saturated muck soil by SPAX-2000 static and dynamic true triaxial testing system (improved). The effects of the effective confining pressure, dynamic stress ratio, loading frequency, on dynamic behaviors of PRD saturated muck soil were investigated. The main results obtained are as follows:(1) Summarized dynamic triaxial test loading conditions of recently researches on the dynamic characteristics of soft soil. Through by loading tests, the feasibility of laboratory test simulation of cyclic loading was demonstrated. By comparing different loading waveform, bias sine waveform can find better simulate the cyclic loading characteristics, generally meet the requirements of laboratory test conditions.(2) Research on the influence of effective confining pressure, dynamic stress ratio, load frequency and other factors to pore pressure of PRD saturated muck soil under cyclic loading. It was found that dynamic stress ratio, load frequency had more significant impact to pore water pressure but effective confining pressure had not. Dynamic stress ratio increases, the greater value of pore pressure in each cycling stage, the faster increasing of pore pressure, the greater stable value of pore pressure. Load frequency decreases, the greater value of pore pressure in each cycling stage, the faster increasing of pore pressure, the greater stable value of pore pressure.By introducing a variable not affected by various factors-the number of cycles N, based on the mathematical model u*= A(lnN)2+Bln N which describe the pore pressure increase and combining test results, a empirical pore pressure fitting formula of PRD saturated muck soil was established to describe the effects of dynamic stress ratio, load frequency, the effective confining pressure to porewater pressure under cyclic loading:(3) Research on the influence of effective confining pressure, dynamic stress ratio, load frequency and other factors to cyclic softening of PRD saturated muck soil under cyclic loading. It was found that dynamic stress ratio, load frequency had more significant impact to softening index but effective confining pressure had not.Dynamic stress ratio increases, the smaller value of softening index in each cycling stage, the faster decaying of softening index, the maller stable value of softening index. Load frequency decreases, the smaller value of softening index in each stage of cycling, the faster decaying of softening index, the maller stable value of softening index.Under cyclic loading, the relationship between softening index 8 and 1g N is nonlinear. By combining formula δ= 1-A(lg N)-B1g N and test results, a empirical softening fitting formula of PRD saturated muck soil was established to describe the effects of dynamic stress ratio, load frequency, the effective confining pressure to cyclic softening under cyclic loading: (4) Research on the influence of effective confining pressure, dynamic stress ratio, load frequency and other factors to strain and strain rate of PRD saturated muck soil under cyclic loading. It was found that dynamic stress ratio, load frequency had more significant impact to strain but effective confining pressure had not.Dynamic stress ratio increases, the greater value of strain in each cycling stage, the faster increasing of strain, the greater stable value of strain. Load frequency decreases, the greater value of strain in each cycling stage, the faster increasing of strain, the greater stable value of strain. There is a good linear relationship between the logarithm of strain rate and number of cycles. Dynamic stress ratio, load frequency had more significant impact to strain. Dynamic stress ratio or load frequency increases, the greater value of strain rate.With the increasing number of cycles, the decay rate of strain rate hardly changed, dynamic stress ratio, load frequency saturated silt soil strain rate reduction rate is not significantly affected.Dynamic stress ratio or load frequency have no impact to decay rate of strain rate. Through the establishment of strain rate-the number of cycles Igarithmic model, a accumulated plastic strain mode of PRD saturated muck soil was indirectly established to describe the effects of dynamic stress ratio, load frequency to accumulated plastic strain under cyclic loading:...