Test on cyclic creep behavior of mucky clay in Shanghai under step cyclic loading

Abstract

Based on the cyclic triaxial test under step loading, the variation of cyclic creep and pore water pressure with increase in cyclic stress ratio (CSR) and load cycle of mucky clay in Shanghai were analyzed. The results show that there are two threshold values of stability cyclic stress ratio and failure cyclic stress ratio during the step loading which divide the development of cyclic creep strain into gradual stability stage, rapid growth stage and instantaneous failure stage. When the stress level is less than the failure cyclic stress ratio, the recoverable elastic strain is nearly linear with CSR. The cyclic creep properties of mucky clay are obviously influenced by the loading frequency under the same stress level.

Deformation Characteristics of Soft Marine Soil Tested under Cyclic Loading with Low Frequency

“…en, the measured value is much closer to the real value, accompanied by the homogenisation and accumulation of the pore pressure in the specimen [7].…”

“…is type of soil usually has a high void ratio, significant compressibility, high water content, low permeability, high structural effects, and notable sensitivity. In this marine environment, the foundation design of nearshore and offshore structures is typically governed by the bearing capacity and serviceability under cyclic loadings [1][2][3][4], as the cyclic loading could induce reductions of strength [5,6] and bearing capacity [7,8], unexpected settlement [3,9], and other geotechnical engineering problems [10,11].…”

“…Since Sangrey et al's study [18], researchers begin to notice that the cyclic deformation response of soft marine soil is greatly influenced by the significant increase in pore pressure due to its low permeability compared with that of sands [19,20]. Tang et al [7] analysed the variation of cyclic deformation and pore pressure with increasing stress ratio and cyclic number of mucky clays in Shanghai and stated that it generates greater recoverable elastic strain, accumulated plastic strain, and residual pore pressure when subjected to the cyclic loading with lower frequency under the same stress level in the frequency section of 0.5-2.5 Hz. Gu et al [21] studied the undrained cyclic behaviour of saturated Wenzhou clays and found that the cyclic response of the specimens is strongly influenced by the variation of confining stress, in terms of pore pressure, development speed of cyclic deformation, and magnitude of cyclic strength, which is more appropriate for the simulation of in situ stress fields than the conventional cyclic triaxial tests with a constant confining pressure.…”

“…However, some of the conclusions in the literature are controversial or have strict application conditions. For example, for the influence of loading frequency, some existing works have indicated that both the accumulated deformation and pore pressure induced by cyclic loading increase with decreasing frequency [7,20,28], whereas other researchers have reported that the frequency has little or no influence on the cyclic deformation and pore pressure [29,30]. Actually, soft soil behaviour under undrained cyclic loading is complex for time-and rate-dependent characteristics [6].…”

Experimental Study on Thermal Balance in Soft Clay Area During GSHP Operation

“…It is reconstituted from undisturbed soil from a typical Shanghai construction site in Tang Town of Pudong New City, east from the Huangpu River. Construction in soft clay encounters issues associated with low permeability, thixotropy, and the rheology of the muddy clay [50][51][52][53]. However, thermal properties are rarely considered.…”