Study on the Engineering Properties of Saturated Red Sandstone

2014 ◽  
Vol 638-640 ◽  
pp. 589-593
Author(s):  
Hong Yi Wang ◽  
Wu Xiu Ding ◽  
Jin Jin Yang
Keyword(s):  
Construction Projects ◽  
Elasticity Modulus ◽  
Triaxial Compression ◽  
Mechanical Damage ◽  
Confining Pressure ◽  
Peak Strength ◽  
Engineering Properties ◽  
Compression Tests ◽  
Red Sandstone ◽  
Slope Excavation

Red sandstone with a strong water softening can cause difficulties of construction projects, especially for slope excavation and support engineering. Therefore, the study on the engineering properties of saturated red sandstone has a important meaning. The mechanical parameters of saturated red sandstone are obtained by the triaxial compression tests. The test results indicate that the ralations between peak strength, elasticity modulus and confining pressure for the saturated specimens are similar with the natural specimens, that is, with the increasing of confining pressure, the peak strength and the elasticity modulus will increase, but the growth rate becomes slowly. Under the same confining pressure, the peak strength and the elasticity modulus of saturated specimen are more smaller than the natural one. The mechanical damage caused by water recedes when the confining pressure increases, so for the geotechnical engineering with larger influence of water, the increasement of confining pressure by the supporting structures is conducive to the stability of rock mass. The research results will provide a theoretical basis for the red sandstone engineering.

Study on Constitutive Mode of Three Typical Rocks Based on Triaxial Compression Test

2012 ◽  
Vol 170-173 ◽  
pp. 322-326
Author(s):  
Kui Chen ◽  
Ren Hua Yang ◽  
Tao Xu ◽  
Ya Jing Qi
Keyword(s):  
Residual Strength ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Digital Design ◽  
Peak Strength ◽  
Design Parameters ◽  
Stress Strain ◽  
Red Sandstone ◽  
Constitutive Mode ◽  
Shield Machine

In order to study the relationship between the design parameters of the shield machine and the strength of rock, the behaviours of rocks under the conventional triaxial compression, the complete stress-strain curves under different confining pressures of three typical rocks, i.e. granite, limestone and red sandstone, were taken out for analysis. From the curves, the values of elastic modulus E and Poisson's ratio μ were gained and the relationships between the following parameters were figured out, which are peak strength versus confining pressure, residual strength versus confining pressure, strain at peak strength versus confining pressure, and strain at residual strength versus confining pressure. According to the values and relationships, the complete stress-strain curves were divided into three parts. For each part, a constitutive equation was established by using the strain softening trilinear elastic-brittle-plastic constitutive model, and all the related parameters in the constitutive equations were also presented, which provide a theoretical foundation for the digital design of the cutter head and cutters of Shield machine.

Strength and deformation behavior of red sandstone under multi-stage triaxial compression

2012 ◽  
Vol 49 (6) ◽  
pp. 694-709 ◽  
Author(s):  
Sheng-Qi Yang
Keyword(s):  
Deformation Behavior ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Single Stage ◽  
Peak Strength ◽  
Red Sandstone ◽  
Triaxial Strength ◽  
Multi Stage ◽  
Strength And Deformation ◽  
The Difference

Based on multi-stage triaxial experimental results of red sandstone with circumferential deformation control, the influence of confining pressure on strength and deformation behavior of red sandstone under multi-stage triaxial compression is investigated. The results show that the confining pressure has an obvious effect on the deformation parameters of red sandstone under multi-stage triaxial compression. A multi-stage triaxial compression experiment with only one specimen can be used to confirm the peak strength of rock under different confining pressures. Under single-stage and multi-stage triaxial compression, the peak strength behavior of red sandstone agrees better with the nonlinear Hoek–Brown criterion than the linear Mohr–Coulomb criterion. However, the difference between single-stage and multi-stage triaxial strength changes with different post-peak deformation values, and the reason for the difference, is discussed. To predict single-stage triaxial strength using the obtained multi-stage triaxial strength with only one specimen, a new method is put forward to revise multi-stage triaxial strength of red sandstone, which testifies to being reasonable. The concluding remarks are very useful and significant for deep geotechnical and underground structural engineering.

scholarly journals Study on Mechanical Properties and Damage Characteristics of Red Sandstone under Freeze-thaw and Load

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Lei Shi ◽  
Yang Liu ◽  
Xiangzhen Meng ◽  
Huimei Zhang
Keyword(s):  
Mechanical Properties ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Damage Variable ◽  
Mechanical Parameters ◽  
Compression Tests ◽  
Internal Damage ◽  
Red Sandstone ◽  
Freeze Thaw ◽  
Total Damage

To analyze the effects of freeze-thaw cycles and confining pressure on the mechanical properties of red sandstone, through freeze-thaw cycles and triaxial compression tests, full stress-strain curves of different freeze-thaw cycles and different confining pressures were obtained. The degradation degree of red sandstone was quantitatively considered from different mechanical parameters of ultimate stress, elastic modulus, and Poisson’s ratio. Based on summarizing the characteristics of rock under freeze-thaw and load, the total damage variable of rock was determined by the reasonable measurement of freeze-thaw damage variable and load damage variable, and a damage constitutive model under freeze-thaw and load was established. The research showed that the freeze-thaw cycles aggravate the degree of rock damage deterioration, the rock stiffness and strength were reduced, and the characteristics of plastic deformation and ductile failure were more obvious. The confining pressure inhibited red sandstone internal damage, and with the increase of confining pressure, the stiffness and strength and the plastic characteristics were increased. In the overall trend, the mechanical parameters had different sensitivity to the degradation effect of freeze-thaw cycles and confining pressure. Regardless of the increase in the number of freeze-thaw cycles or confining pressure, the strain softening modulus tended to decrease gradually, and red sandstone plastic damage became more obvious after the stress peak. The total damage evolution path of red sandstone reflected the nonlinear influence of freeze-thaw and load on the total damage propagation. The research results provide theoretical support for the improvement of the technology of the effluent coal rock in Balasu Coal Mine.

scholarly journals Mechanical Behavior of Coupled Elastoplastic Damage of Clastic Sandstone of Different Burial Depths

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1640
Author(s):  
Yu Zhang ◽  
Lu Wang ◽  
Goangseup Zi ◽  
Yan Zhang
Keyword(s):  
Plastic Deformation ◽  
Mechanical Behavior ◽  
Oil And Gas ◽  
Triaxial Compression ◽  
Mechanical Damage ◽  
Confining Pressure ◽  
Internal Variables ◽  
Burial Depth ◽  
Compression Tests ◽  
Elastoplastic Damage

Clastic sandstone is widely distributed in oil and gas reservoirs; its internal structure has many micro-defects. Under different stress environments of burial depth, significant damage evolution and plastic deformation easily occur. A series of triaxial compression tests were performed to study the coupled elastoplastic damage mechanical behavior of clastic sandstone samples at different burial depths ranging from 581.28 m to 979.82 m. Results reveal that the stress-strain responses of clastic sandstone samples exhibit significant nonlinear and softening characteristics. The mechanical behavior is due to the coupling of plastic deformation and mechanical damage. Plastic and damage internal variables cause damage stiffness degradation and plastic flow. Considering the coupling of elastoplastic damage in the loading process, an elastoplastic damage coupling model is proposed to study the mechanical behavior of different burial depth clastic sandstones. The model can effectively describe the mechanical behavior of clastic sandstone, such as the volume compression and dilatancy transformation, plastic hardening and damage softening, which are in good agreement with the experimental results. Furthermore, the mechanical behavior of the clastic sandstone shows a dependency on the confining pressure and burial depth. The load-bearing capacity and the ability to resist deformation of the clastic sandstone are improved as the confining pressure and burial depth increase. Relevant results can provide reliable basis for the safe exploitation of oil and gas engineering.

scholarly journals Loading Rate Dependence of Rock Strength Under Triaxial Compression

2021 ◽  
Vol 9 ◽  
Author(s):  
Yang Tang ◽  
Hailong Zhang ◽  
Jiang Xu ◽  
Seisuke Okubo ◽  
Xinrong Liu
Keyword(s):  
Strain Rate ◽  
Residual Strength ◽  
Rock Strength ◽  
Loading Rate ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Rate Dependence ◽  
Peak Strength ◽  
Compression Tests ◽  
Tenfold Increase

Knowledge regarding the time-dependent behavior of rocks is essential to estimate the long-term deformation and stability of underground structures. The rock strength increases with the increasing loading rate. However, the loading rate dependence in postfailure regions under confining pressure remains unclear. In this study, triaxial compression tests were conducted on four types of rocks to examine the loading rate dependence in both peak and postfailure regions. Results demonstrate that an increase in residual strength with a tenfold increase in the strain rate was approximately proportional to 4% of the residual strength. Furthermore, the increase in peak strength with a tenfold increase in the strain rate increased at a rate of approximately 4% of peak strength. The obtained results were applicable to all the sample rocks and can be easily employed for improving the constitutive equations. Finally, the effect mechanism of the confining pressure on the loading rate dependence of rock strength is discussed.

scholarly journals Triaxial Compressive Failure Characteristics and Constitutive Model Study of Jurassic-Cretaceous Weakly Cemented Sandstone

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Jinlong Cai ◽  
Wei Zou
Keyword(s):  
Constitutive Model ◽  
Residual Strength ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Ductile Failure ◽  
Mathematical Expression ◽  
Confining Pressure ◽  
Mining Area ◽  
Peak Strength ◽  
Correction Coefficient

A conventional triaxial compression test of Jurassic-Cretaceous typical weakly consolidated sandstone from a mining area in Ordos, China, was conducted using an MTS816 tester. Results showed that, before the peak, the rock had a distinct yield stage. When the specimen reached its peak strength, the strength decreased rapidly and showed an obvious brittle failure. When the confining pressure was increased to 15 MPa, the decrease of strength was slow and the rock tended toward ductile failure. With the increase of confining pressure, the cyclic strain initially increased slightly, whereas the volumetric strain increased greatly and the rock sample was in a compression state. When the load reached a critical value, the curve was reversely bent, resulting in volume expansion, whereas the peak strength, residual strength, and elastic modulus increased with confining pressure, and Poisson’s ratio decreased with the confining pressure. In the model based on macroscopic failure rock, the expression of the relationship between fracture angle and confining pressure provided a solid theoretical basis for the direction and failure mode of the macroscopic crack. Based on the rock strength theory and Weibull random distribution assumption of rock element strength, the damage variable correction coefficient was introduced when the residual strength was considered. Then, the mathematical expression of the 3D damage statistical constitutive model was established. Finally, the theoretical curve of the established constitutive model was compared with the triaxial test curve, which showed a high degree of coincidence.

scholarly journals Appraisal of Geotechnical Characteristics of Ormara Soil, Baluchistan, Pakistan

2019 ◽  
Vol 10 (3) ◽  
pp. 22-26
Author(s):  
Abdul Jabbar Khan ◽  
Naveed Ahsan ◽  
Muhammad Sanaullah ◽  
Gulraiz Akhter
Keyword(s):  
Triaxial Compression ◽  
Liquid Limit ◽  
Soil Samples ◽  
Engineering Properties ◽  
Clay Layer ◽  
Compression Tests ◽  
Geotechnical Characteristics ◽  
Density Values ◽  
Construction Plans ◽  
Triaxial Compression Tests

Ormara is located 240 km west of Karachi which is a coastal and port city (25° 16' 29N, 64° 35' 10E) ofPakistan. Present study evaluates engineering properties of soils of Ormara for future construction plans and possibleexpansions in the area. Fifty bore holes were done in study area at depths of 20m, 40m and some (10 bore holes) were60m deep. The study area was divided into three major zones i.e. Foot hills, on-shore and off-shore. Groundwater wasencountered at depths of 2.75m on onshore and offshore zones and at 3.65m depth in foothill zone. Laboratory testingi.e. moisture content (12 to 38 %), liquid limit (from 26 to 34), plasticity index (10 to 18) of soil samples indicate thatsoils are low plastic to moderate plastic in nature. Soil samples of granular soils indicate angles of internal friction (ø)varying from 260- 36ºin upper sand layers while 260 to 30º in lower silt layers (encountered after the clay layer) andCohesion ranges 0 to 0.04kg/cm2 in all three zones. Further, unconsolidated undrained triaxial compression tests on aclayey soil sample indicated an undrained cohesion value of 28 kPa. Density values ranges from 1.6 to 2.05gm/cm3.Consolidation (Cv = 0.20 to 0.40 cm2/minute, Cc = 0.149 to 0.17) has been calculated for clay layer. Chemical testscarried out on soil samples indicated that soil and water both are reactive aggressively and may cause corrosion to steeland concrete disintegration.

scholarly journals Triaxial Testing of Geosynthetics Reinforced Tailings with Different Reinforced Layers

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1943
Author(s):  
Fu Yi ◽  
Changbo Du
Keyword(s):  
Triaxial Compression ◽  
Friction Angle ◽  
Confining Pressure ◽  
Test Results ◽  
Compression Tests ◽  
Strength Index ◽  
Stress Strain ◽  
High Confining Pressure ◽  
Zhang Model ◽  
Triaxial Compression Tests

To evaluate the shear properties of geotextile-reinforced tailings, triaxial compression tests were performed on geogrids and geotextiles with zero, one, two, and four reinforced layers. The stress–strain characteristics and reinforcement effects of the reinforced tailings with different layers were analyzed. According to the test results, the geogrid stress–strain curves show hardening characteristics, whereas the geotextile stress–strain curves have strain-softening properties. With more reinforced layers, the hardening or softening characteristics become more prominent. We demonstrate that the stress–strain curves of geogrids and geotextile reinforced tailings under different reinforced layers can be fitted by the Duncan–Zhang model, which indicates that the pseudo-cohesion of shear strength index increases linearly whereas the friction angle remains primarily unchanged with the increase in reinforced layers. In addition, we observed that, although the strength of the reinforced tailings increases substantially, the reinforcement effect is more significant at a low confining pressure than at a high confining pressure. On the contrary, the triaxial specimen strength decreases with the increase in the number of reinforced layers. Our findings can provide valuable input toward the design and application of reinforced engineering.

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