Characterizing the Effect of Water Content on Small-Strain Shear Modulus of Qiantang Silt

Due to the impact of natural and artificial influence, such as waves, tides, and artificial dewatering, the small-strain shear modulus of soils may vary with the water content of soil, causing deformation of excavations and other earth structures. The present study used a resonant column device to investigate the effects of water content, void ratio, and confining pressure on the small-strain shear modulus of a silt extracted from an excavation site near Qiantang River in Hangzhou, China. The test results revealed that the effects of the three factors are not coupled and can be characterized by three individual equations. In particular, the small-strain shear modulus decreases with increasing water content under otherwise similar conditions, which can be characterized by a power function. The classical Hardin’s equation is modified to consider the effect of water content by introducing an additional function of water content.

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Impacts of matric suction equalization on small strain shear modulus of soils during air drying

Canadian Geotechnical Journal ◽

10.1139/cgj-2019-0742 ◽

2020 ◽

Vol 57 (12) ◽

pp. 1982-1997

Author(s):

Thang Pham Ngoc ◽

Behzad Fatahi ◽

Hadi Khabbaz ◽

Daichao Sheng

Keyword(s):

Shear Modulus ◽

Water Content ◽

Soil Sample ◽

Closed System ◽

Small Strain ◽

Matric Suction ◽

Drying Process ◽

Air Drying ◽

Small Strain Shear Modulus ◽

The Impact

In this study, a weight-control bender element system has been developed to investigate the impact of matric suction equalization on the measurement of small strain shear modulus (Gmax) during an air-drying process. The setup employed is capable of measuring the shear wave velocity and the corresponding Gmax of the soil sample in either an open system in which the soil sample evaporates freely or in a closed system that allows the process of matric suction equalization. The comparison between measurements of Gmax in the open and closed systems revealed underestimations of Gmax when matric suction equalization was ignored due to the nonuniform distribution of water content across the sample cross-sectional area. This study also investigated the time required for matric suction equalization tse to be established for samples with different sizes. The experimental results indicated two main mechanisms driving the matric suction equalization in a closed system during an air-drying process, namely the hydraulic flow of water and the flow of vapour. While the former played the key role when the micropores were still saturated at the high range of water content, effects of the latter increased and finally dominated when more air invaded the micropores at lower water contents.

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Piezoelectric Ring Bender for Characterization of Shear Waves in Compacted Sandy Soils

Sensors ◽

10.3390/s21041226 ◽

2021 ◽

Vol 21 (4) ◽

pp. 1226

Author(s):

Dong-Ju Kim ◽

Jung-Doung Yu ◽

Yong-Hoon Byun

Keyword(s):

Shear Modulus ◽

Water Content ◽

Shear Wave ◽

Wave Velocity ◽

Shear Wave Velocity ◽

Shear Waves ◽

Small Strain ◽

The Other ◽

Compacted Soils ◽

Small Strain Shear Modulus

Shear wave velocity and small-strain shear modulus are widely used as the mechanical properties of soil. The objective of this study is to develop a new shear wave monitoring system using a pair of piezoelectric ring benders (RBs) and to evaluate the suitability of RB in compacted soils compared with the bender element and ultrasonic transducer. The RB is a multilayered piezoelectric actuator, which can generate shear waves without disturbing soils. For five compacted soil specimens, the shear waves are monitored by using three different piezoelectric transducers. Results of time-domain response show that the output signals measured from the RB vary according to the water content of the specimen and the frequency of the input signal. Except at the water content of 9.3%, the difference in the resonant frequencies between the three transducers is not significant. The shear wave velocities for the RB are slightly greater than those for the other transducers. For the RB, the exponential relationship between the shear wave velocity and dry unit weight is better established compared with that of the other transducers. The newly proposed piezoelectric transducer RB may be useful for the evaluation of the shear wave velocity and small-strain shear modulus of compacted soils.

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