Mechanical Properties of Soft Soil considering the Influence of Unloading Stress Paths

Huang, Wei; Li, Junjie; Lu, Yuming; Li, Dongsheng; Mou, Yaqing; Wu, Xuheng; Jiang, Zhijian; Li, Ziyun

doi:10.1155/2021/8813882

Cited by 6 publications

(4 citation statements)

References 11 publications

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“…Te combined lithology of the roof and foor of the main commercial coal seams in Xiangshui Coal Mine is mainly composed of weak siltstone, argillaceous siltstone, silty mudstone, mudstone, and coal seam, which belong to fne deposits [24][25][26][27] in general. Tere are many coal layers, but most of them are of small thickness, generally less than 1.3-3.5 m. Te roof and foor are dominated by thin layers of mudstone.…”

Section: Lithofacies Of the Coal Measures Andmentioning

confidence: 99%

Experimental Study on the Damage and Crack Evolution Characteristics of TS-RCR Structural Bodies under Cyclic Loading and Unloading

Xie,

Chen,

Fang

et al. 2023

Advances in Civil Engineering

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Four representative TS-RCR (three-soft rock-coal-rock) structural bodies were selected according to the lithofacies analysis of coal measures in the Xiangshui Coal Mine, Guizhou, China, to analyze the mechanical properties, internal structure damage characteristics, and crack evolution law of the TS-RCR structural body composed of a soft roof, a soft floor, and soft coal seams. The mechanical model of the TS-RCR structural body was proposed. (1) The stress-strain curves of TS-RCR structures with different lithologies under cyclic loading and unloading show a change rule of sparsity, density, and sparsity with the increased cycles. The deformation of TS-RCR structures under cyclic loading and unloading can be divided into four stages. When the height ratio of the TS-RCR structural body was the same, the higher the strength of the upper and lower rocks, the more cycles the TS-RCR structural body had, and the denser the cyclic loading and unloading curve. On the contrary, the fewer cycles the TS-RCR structural body had, the sparser the cyclic loading and unloading curve. (2) The T2 (transverse relaxation time) spectrum curves of the structural bodies were monitored at about 1 and 10 ms, and two obvious peaks were detected, indicating micropores and mesopores with a large volume in the structural body. Signal intensity increased at the relaxation time of 1 ms, decreased at 10–100 ms, and increased slightly at 100–1000 ms. The pore structure of the structural body with different lithologies changed significantly with the increased cycle number. (3) The damage and failure process of the structural body was roughly divided into three periods according to the time-history analysis of acoustic-emission AF (the ratio of acoustic-emission ringing count to duration) of the structural body: the active period with a relatively low AF value (AF < 60 kHz) in the 1st-2nd cycles; the rising period with a relatively stable increase of the AF value in the 3rd-4th cycles; and the explosive period with a relatively high AF value (AF ≥ 60 kHz) in the 5th cycles. According to the relationship between the RA (the ratio of the rise time to the amplitude of the acoustic-emission-detection wave) value and time, the evolution law of the RA value and AF value of structures with different lithologies is similar in different periods under cyclic loading and unloading.

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Section: Lithofacies Of the Coal Measures Andmentioning

confidence: 99%

Experimental Study on the Damage and Crack Evolution Characteristics of TS-RCR Structural Bodies under Cyclic Loading and Unloading

Xie,

Chen,

Fang

et al. 2023

Advances in Civil Engineering

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“…The mechanical properties of soft clay, such as deformation and strength, are related to stress paths [1,2] and corresponding rate effects [3][4][5] owing to the characteristics of high clay grain content, high moisture content, and large pore ratio, among others. The excavation of a foundation pit is a typical unloading project in geotechnical engineering.…”

Section: Introductionmentioning

confidence: 99%

“…Lim et al [9] demonstrated that the unloading mechanical parameters of soft soils can be used to accurately calculate the excavation deformations of foundation pits under undrained conditions. Huang et al [1] conducted K 0 consolidation undrained shear tests on Shenzhen soft soil under the influence of unloading stress paths; the results showed variation in the unloading strength and initial shear modulus of soils under unloading stress paths, and the deformation properties of soils were greatly influenced by the unloading stress paths. Jia et al [10] performed axial loading and lateral unloading shear tests on Wenzhou soft clay using a stress-path triaxial apparatus and proposed a four-parameter stress-strain curve model based on the deformation mechanism of structured soils and incremental linear elasticity theory.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Mechanical Properties of Structured Clay under Different Unloading Rates and Unloading Stress Paths

Zang

Zhang

et al. 2023

Buildings

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Consolidated undrained triaxial shear tests were performed on undisturbed saturated structured clay at three unloading rates (0.1, 0.25, and 2.5 kPa/min) using a GDS triaxial system to determine the effects of different unloading rates and unloading stress paths on the stress–strain relationship, pore pressure variation, and failure strength characteristics of Zhanjiang structured clay. Microstructural changes in the clay were observed during shear tests at different unloading rates. Furthermore, the obtained stress–strain relationship indicates strain-softening under different unloading stress paths. Under the same axial strain, a larger unloading rate caused a larger deviatoric stress. Under the same conditions, the higher the confining pressure, the greater the peak pore pressure, the smaller the unloading rate, the greater the pore pressure development, and the greater the variation in the pore pressure. Moreover, the undrained shear strength increased with an increase in the unloading rate from 0.1 to 2.5 kPa/min. The change in the unloading rate had a greater effect on the undrained strength under the passive tensile path than that under the passive compression path. The microstructure of the Zhanjiang structured clay changed after shear tests at different unloading rates, exhibiting various degrees of adjustment in the particle arrangement, contact relations, pore sizes, and shapes.

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“…Therefore, the study of physical and mechanical properties, as well as the mineral composition of deep-sea soils, is crucial. The basic physical properties of deep-sea soils can be determined by geotechnical tests [15][16][17][18]. To better understand the engineering properties of deep-sea soils, many scholars have researched this topic.…”

Section: Introductionmentioning

confidence: 99%

Normalized Stress–Strain Behavior of Deep-Sea Soft Soils in the Northern South China Sea

Yang

Kou

et al. 2022

JMSE

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The study of the physical and mechanical properties of marine soil is of great importance for marine geohazard prediction, submarine energy extraction, and submarine foundation design. In this study, a series of basic geotechnical tests and triaxial compression tests are performed on samples taken from the Shenhu sea area in the South China Sea (SCS). Physical and mechanical properties, particularly normalized stress–strain behavior, are investigated. The microstructural and mineralogical characterization is carried out, through scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results indicated that the sample could be classified as high-plasticity silt (MH) with high water content and high compressibility, that the soil has the highest quartz content in its mineral composition, a loose skeleton composed of flocculent structures under the microscope and is distributed with the remains of marine organisms. Furthermore, a new stress–strain-normalized condition is theoretically derived, based on the hyperbola function. In this condition, the concept of standard normalized factor, which is defined as the ultimate value of principal stress difference, is introduced. Meanwhile, the normalized stress–strain relationship of soft soil from the SCS is established under consolidated undrained conditions and the results of the model are compared with the experimental results, with a good normalization effect. It is believed that the work presented in this paper could contribute to the design and construction of offshore engineering.

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Mechanical Properties of Soft Soil considering the Influence of Unloading Stress Paths

Cited by 6 publications

References 11 publications

Experimental Study on the Damage and Crack Evolution Characteristics of TS-RCR Structural Bodies under Cyclic Loading and Unloading

Experimental Study on the Damage and Crack Evolution Characteristics of TS-RCR Structural Bodies under Cyclic Loading and Unloading

Experimental Study on Mechanical Properties of Structured Clay under Different Unloading Rates and Unloading Stress Paths

Normalized Stress–Strain Behavior of Deep-Sea Soft Soils in the Northern South China Sea

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