Analysis and Discussion about the Field Direct Shear Test Results of the Recently Deposited Sand and Cobble Stratum

The basic physical and mechanical properties of Libyan soil are analyzed through some experiments, including direct shear test, grading analysis test and compression test. According to the test results, the soil is named as low liquid limit silt featured by weak strength, high compressibility and permeability, which directly influences sub-grade stability, durability and pavement’s usability. In order to solve these problems, measures are discussed from two aspects, namely, soil improvement and construction method. The strength of the soil is apparently increased by the cement and lime adding, and the compressibility is decreased at the same time. And the rising height of capillary water reducing and protection forms for silt soil slope are also proved to be effective in the subgrade construction.

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Effect of weathering on the compressibility and shear strength of a natural clay

Canadian Geotechnical Journal ◽

10.1139/t06-028 ◽

2006 ◽

Vol 43 (6) ◽

pp. 618-625 ◽

Cited By ~ 21

Author(s):

Giovanni Gullà ◽

Maria Clorinda Mandaglio ◽

Nicola Moraci

Keyword(s):

Shear Strength ◽

Direct Shear Test ◽

Shear Test ◽

Direct Shear ◽

Test Results ◽

Natural Clay ◽

Standard Equipment ◽

Overconsolidated Clays ◽

Weathering Process

In situ, seasonal changes expose soils to frequent wettingdryingfreezingthawing cycles. Such processes can favour and trigger shallow instabilities controlled by the weathering process. This paper presents an experimental study carried out to investigate the effects of the weathering process, caused by the wettingdryingfreezingthawing cycles, on the compressibility and shear strength of a natural clay. Several specimens were trimmed from block samples of overconsolidated clays taken from a slope in south Calabria, Italy. Specimens were subjected to wettingdryingfreezingthawing cycles of different durations and then tested with standard equipment (oedometer and direct shear). Test results show that the wettingdryingfreezingthawing cycles caused a change in the initial microstructure that produced a decrease in the compression index and an increase in the swelling index. Moreover, the direct shear test results show a decrease in the peak shear strength and demonstrate that a larger reduction occurs in the first month of weathering cycles. The intense cycles performed in the laboratory produced a decay of compressibility and a shear strength approaching reconstituted values. The conclusions are important when choosing the shear strength parameters required when studying shallow landsliding in clay slopes.Key words: weathered clay, structure, cycle of degradation, shallow instability.

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Comparative Study in Method of Compaction by Consolidated Drained and Direct Shear Test

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences ◽

10.37934/arfmts.78.2.143152 ◽

2020 ◽

Vol 78 (2) ◽

pp. 143-152

Author(s):

Abdul Samad Abdul Rahman ◽

N. Sidek ◽

Juhaizad Ahmad ◽

N. Hamzah ◽

M. I. F. Rosli

Keyword(s):

Shear Strength ◽

Bearing Capacity ◽

Triaxial Test ◽

Direct Shear Test ◽

Shear Test ◽

Void Ratio ◽

Direct Shear ◽

Test Results ◽

Stress Strain ◽

Strain Behaviour

Soil compaction has been a common practice in the construction of highways, embankments, earth dams and other related structures where the condition of the soil is high in void ratio and therefore having a very low in bearing capacity. Therefore, the soil needs to be compacted in order to minimize the void ratio and in the same time would results in having a very high bearing capacity to sustain load. Nevertheless, only a few researches have been done to investigate the method of compaction using different energy on the behavior of shear strength by consolidated drained and direct shear test. In this research, the effect of different compaction in energy of 25 number of blows compared to 40 number of blows on the stress-strain behaviour of drained triaxial test has been done and findings of the data are to be compared with direct shear test. Results reveal that there is an increase in soil unit weight by using different energy in compaction with an increase of 5% from 1790 kg/m3 to 1880 kg/m3 for 25 and 40 number of blows respectively. However, the stress-strain behaviour of the specimens shows differently when compared between consolidated drained triaxial and direct shear test. The shear strength for direct shear-stress is at higher value compared to drained triaxial test. For drained triaxial test, results reveal that the effective friction angles are increase only about 1% from 37° to 38°. This is due to the soil particles rearranging itself with the different applied pressures thus eliminating the effects of different energy on the shear strength of the specimens. However, for direct shear test, the shear strength increases drastically from 29° to 32°. The increase of the shear strength is more likely influence by the soil particle arrangement due to the impact of the energy of the no of blows to the desired specimen.

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