Analysis Of Triaxial Tests Research Articles

Triaxial test analysis and discrete element simulation of CFBC

In order to explore the mechanical behavior and crack propagation of cement fly ash stabilized brick-concrete gravel (CFBC) base mixture under three-dimensional compression, firstly, the triaxial loading tests of three different proportions of mixtures were carried out through laboratory tests. The axial load is controlled by a load control loading system, the sampling frequency is 5 Hz, and the triaxial specimen is loaded at a rate of 0.1 MPa /s.The stress–strain curves of the mixture under four different confining pressures were obtained, and the failure characteristics and strength characteristics were analyzed. Secondly, the SEM analysis of the specimens under different confining pressures was carried out, and the microstructure parameters of the mixture under four different confining pressures of 0 MPa, 0.5 MPa, 1.0 MPa and 1.5 MPa were studied based on the PCAS analysis software. On this basis, a three-dimensional discrete element model was established to numerically reproduce the triaxial test of the specimen. The results show that the failure mode of the specimen is mainly related to the confining pressure, and the crack shape has the characteristics of top-down in the direction of principal stress.Through the stress–strain curve, it can be seen that with the increase of confining pressure, the peak stress of the specimen is also increasing. In the BCA1 ratio, the peak stress of the 1.5 MPa confining pressure is increased by 23 % compared with the non-confining pressure. In addition, the cement fly ash stabilized brick-concrete gravel mixture specimen has a larger bearing capacity than other concrete brittle materials.PCAS pore analysis showed that the main controlling factors affecting the porosity of the mixture were brick content and confining pressure, which in turn affected the shear strength and peak stress of the mixture, and the porosity of BCA1 < BCA3 < BCA5; the numerical simulation results show that the failure mode and stress–strain curve of the specimens with the shear strength error of less than 3 % and the friction angle error of less than 6 % are in good agreement. The maximum displacement particle clusters appear on the upper and lower edges of the specimen, and the sliding zone angle of the specimen is about 45° under all stress paths except the horizontal sliding zone under the uniaxial stress state, which reflects that the numerical model is consistent with the mechanical response at the macro scale. The use of three-dimensional discrete element models in the field of construction engineering can simulate and optimize the use of the above materials in construction sites to minimize waste and maximize efficiency.

Stabilization of expansive black cotton soil using bioenzymes produced by ureolytic bacteria

Soil stabilization is the art and science of improving the engineering properties of soils. The properties of problematic soils can be improved by blending appropriate amount of insitu soil, aggregates and bioenzymes. In the present study, four bacterial strains: Sporosarcina pasteurii, Bacillus paramycoides, Citrobacter sedlakii, and Enterobacter bugadensis were used to produce bioenzymes using urea supplemented molasses as a substrate via submerged fermentation. The crude bioenzyme was mixed with modified soil blended with 40% black cotton soil, 30% aggregate and 30% river sand; then tested after curing for 7 days. The test results revealed that except soil samples treated with bioenzyme of Enterobacter bugadensis, all treated soil samples showed improved plasticity index (18–55%) and liquid limit (5–44%). Soil samples treated with bioenzyme of Bacillus paramycoides, Citrobacter sedlakii and Sporosarcina pasteurii showed higher CBR values of 12.9%, 12.27%, and 11.95% respectively. On the other hand, free swell showed reduction in soil samples treated with bioenzymes of Sporosarcina pasteurii (47.37%), Bacillus paramycoides (30%), and Citrobacter sedlakii (10.53%). The highest percentage improvement of linear shrinkage was recorded for soil sample treated with bioenzymes of Sporosarcina pasteuri (39.65%), followed by Permazyme (10.44%), Citrobacter sedlakii (8.4%) and Bacillus paramycoides (8.34%). Whereas, the highest percentage improvement in MDD was recorded in permazyme treated soil (11.92%) followed by molasses (8.29%), Bacillus paramycoides (1.92%), and Enterobacter bugadensis (0.73%). The lowest optimum moisture content (9.3%) was recorded in soil treated with permazyme. Triaxial test analysis also showed improvement in both cohesion and angle of friction in bioenzyme treated soils. From the test results it was concluded that it is possible to treat expansive black cotton soils using bioenzymes produced from low cost substrates such as molasses and reduce the cost of construction and environmental carbon emission.

Dynamic triaxial test analysis of reinforced gravel soil under cyclic loading

Dynamic triaxial test analysis of reinforced gravel soil under cyclic loading

Deformations and liquefaction of granular soils in plane strain conditions

Abstract An incremental model is proposed to describe pre-failure behaviour of granular soils in plane strain conditions. The model has been derived from an approach applied in the analysis of triaxial tests. We have applied the methods of tensor algebra to transfer our triaxial results to a 2D case. The model describes the pre-failure deformations of fully drained sands and phenomena associated with undrained response such as static liquefaction. This model has a simple structure in the form of incremental equations. For some simple loading paths, these equations can be integrated analytically. For more complex loading paths a simple numerical algorithms will be sufficient. The model takes into account an initial anisotropy of soil which is ignored in most models. It also takes into account the initial state of soil, defined as rather contractive or dilative, in addition to classical geotechnical division into loose and dense sands. The proposed constitutive equations allow the study of pre-failure instabilities of sand, and some examples are presented.We have also derived analytically the equation for an instability line.

Comparison Of Failure Criteria For Jointed Rock Masses

This paper compares two different failure strength criteria for rock; the popular non-linear Hoek and Brown failure criterion and a simple non-linear failure criterion recently proposed by Ramamurthy. Equivalent continuum analyses of jointed rock masses have been carried out using program FLAC with each selected failure criterion. The constitutive behaviour of the rock mass is represented by Mohr-Coulomb model in both cases, which is modified by applying the respective failure criterion using special subroutines. Numerical analysis of triaxial tests on intact and jointed rocks has been carried out first and results have been validated against data from experiments. Further, a case study of an underground power cavern has been analysed using both of these failure criteria and the displacements obtained from the analyses were compared with the field measurements. This study brought out the relative merits and demerits of the two failure criteria when applied to the field problems and confirmed that the simple failure criterion proposed by Ramamurthy could be applied with confidence for the analysis of jointed rock masses.