scholarly journals The Tensile Strength of Loess in Northwest China by Unconfined Penetration Test and the Distinct Element Simulation

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Xuyang Wu ◽  
Yun Bao ◽  
Mingyang Ren ◽  
Qingguo Liang
Keyword(s):  
Tensile Strength ◽  
Tensile Stress ◽  
Distinct Element ◽  
Friction Angle ◽  
Northwest China ◽  
Penetration Test ◽  
Element Simulation ◽  
Force Transfer ◽  
Fracture Development ◽  
Tensile Fractures

The unconfined penetration test (UP test) is one of the indirect methods to measure the tensile strength of soils. Through a series of UP tests of undisturbed and remolded loess, the split angle (α) of the wedge body which was shaped in the process of the experiment was discussed. And then, the particle movement, the force transfer, and the fracture development law of the sample were studied by the distinct element method (PFC2D). The experiment and numerical simulation results show the following: (1) the split angle (α) presents an exponential decrease with tensile strength (σt) and a linear decrease with internal friction angle (φ); (2) K that can be written as tan (2α + φ) is a coefficient to calculate tensile strength, which is equal to 2.00 for remolded loess and 1.50 for undisturbed loess; (3) the distinct element simulation shows that the resisting force by the UP test comes from both tensile stress and shear stress; (4) the tensile fractures and shear fractures appear at almost the same time when the tensile stress is approximately 70% of tensile strength.

scholarly journals Dynamic Stability Analysis of Slope Subjected to Surcharge Load considering Tensile Strength Cut-Off

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Guangdong Lv ◽  
Yi He ◽  
Bingsi Wei
Keyword(s):  
Tensile Strength ◽  
Tensile Stress ◽  
Dynamic Stability ◽  
Friction Angle ◽  
Classical Solutions ◽  
Seismic Load ◽  
Critical Acceleration ◽  
Ground Shaking ◽  
Surcharge Load ◽  
Seismic Forces

Surcharge slopes are more vulnerable to instability under the effects of earthquake ground shaking, especially considering the tensile stress. In order to account for the adverse factors of seismic forces and tensile stress, the theory of soil with tensile strength cut-off is deduced and analyzed using the upper bound limit analysis method in this paper. Combined with the quasistatic analysis, the equation of critical acceleration expression for surcharge slope subjected to the dynamic conditions has been evaluated. By using the improved Newmark method, permanent displacements have been analyzed in the case of the classical earthquake ground motions. In addition, optimization algorithm has been undertaken, in which several influencing factors such as slope inclination, internal friction angle, surcharge factor, seismic load, and tension cut-off coefficient have been taken into account, and some results are verified with the classical solutions and FEM results. The results concluded the following: (1) The outcomes of verification results are accurate. (2) The critical acceleration of the slope is significantly affected by tension cut-off with the increasing of surcharge factor and seismic effects. (3) The permanent displacements of surcharge slope considering the tensile strength cut-off can be even 2 times of the traditional analysis; meanwhile, with more reduction of tensile strength, the cumulative displacements increase rapidly. Therefore, considering the influence of tensile strength cut-off is fundamental to the dynamic stability design of surcharge conditions.

Analysis on Cracking Cause and Propagation Trend of Concrete Dam

2013 ◽  
Vol 444-445 ◽  
pp. 831-835
Author(s):  
Qin Chen ◽  
Ya Qi Gong ◽  
Yong Feng Qi
Keyword(s):  
Tensile Strength ◽  
Tensile Stress ◽  
Flow Direction ◽  
Three Dimensional ◽  
Concrete Surface ◽  
Concrete Dam ◽  
Sudden Drop ◽  
Element Simulation ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Some cracks are observed in a heightening project of a concrete gravity. In order to investigate and solve this problem, the three-dimensional finite element simulation and nonlinear cracking analysis are implemented in this paper to analyze the causes of cracks and their propagation trends. This work is helpful to design the proper crack controlling plans. The research shows that large tensile stress has accumulated during construction, especially after an early air temperature sudden drop in November, the tensile stress increases 3MPa in general on the concrete surface, which exceeds the tensile strength of concrete and causes cracking. Therefore, the crack is the result of both the accumulated temperature stress during construction and temperature sudden drop. The crack will further propagate during another temperature sudden drop, but extended range is limited. If concrete tensile strength is greater than 2.5MPa, the cracks will not penetrate throughout the dam body along the water flow direction.

Distinct Element Simulation of Faulted Reservoir Behavior

1995 ◽  
Vol 10 (03) ◽  
pp. 141-147 ◽  
Author(s):  
A.H. Makurat ◽  
Marte Gutierrez ◽  
Borge Knapstad ◽  
J.H. Johnsen ◽  
Andreas Koestler
Keyword(s):  
Distinct Element ◽  
Element Simulation

Assessment of the range of variation of Nγ from 60 estimation methods for footings on sand

2013 ◽  
Vol 50 (7) ◽  
pp. 793-800 ◽  
Author(s):  
Edgar Giovanny Diaz-Segura
Keyword(s):  
Friction Angle ◽  
Standard Penetration Test ◽  
Estimation Methods ◽  
Penetration Test ◽  
In Situ Tests ◽  
Vertical Loading ◽  
Simplified Method ◽  
Bearing Capacity Factor ◽  
Range Of Variation

The range of variation of the bearing capacity factor, Nγ, was assessed using 60 estimation methods for rough footings on sand subjected to static vertical loading. The influence on the Nγ values of the use of correlations for the estimation of the friction angle, [Formula: see text], derived from in situ tests was also assessed. The analysis shows a marked dependency on the methods used to determine Nγ, showing differences for the same [Formula: see text] values of up to 267% between estimated values. Uncertainty in the estimation of [Formula: see text], due to the use of correlations with in situ tests, leads to a range of variation for Nγ higher than that seen using the 60 estimation methods. Finally, given the regular use of the in situ standard penetration test (SPT) on sands, and based on a series of analyses using finite elements, a simplified method in terms of the SPT N-values is proposed for estimation of Nγ in footings on sands.

scholarly journals AN INVESTIGATION ON THE EFFECTS OF MICRO-PARAMETERS ON THE STRENGTH PROPERTIES OF ROCK

2021 ◽  
Vol 36 (1) ◽  
pp. 111-119
Author(s):  
Behzad Jafari Mohammadabadi ◽  
Kourosh Shahriar ◽  
Hossein Jalalifar ◽  
Kaveh Ahangari
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Friction Coefficient ◽  
Critical Stress ◽  
Friction Angle ◽  
Strength Properties ◽  
Brazilian Tensile Strength ◽  
The Relationship

Rocks are formed from particles and the interaction between those particles controls the behaviour of a rock’s mechanical properties. Since it is very important to conduct extensive studies about the relationship between the micro-parameters and macro-parameters of rock, this paper investigates the effects of some micro-parameters on strength properties and the behaviour of cracks in rock. This is carried out by using numerical simulation of an extensive series of Uniaxial Compressive Strength (UCS) and Brazilian Tensile Strength (BTS) tests. The micro-parameters included the particles’ contact modulus, the contact stiff ness ratio, bond cohesion, bond tensile strength, the friction coefficient and the friction angle, and the mechanical properties of chromite rock have been considered as base values of the investigation. Based on the obtained results, it was found that the most important micro-parameters on the behaviour of rock in the compressive state are bond cohesion, bond tensile strength, and the friction coefficient. Also, the bond tensile strength showed the largest effect under tensile conditions. The micro-parameter of bond tensile strength increased the rock tensile strength (up to 5 times), minimized destructive cracks and increased the corresponding strain (almost 2.5 times) during critical stress.

scholarly journals Experimental Investigation on Mechanical Properties of In Situ Cemented Paste Backfill Containing Coal Gangue and Fly Ash

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xinguo Zhang ◽  
Shichuan Zhang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Fly Ash ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Friction Angle ◽  
Coal Gangue ◽  
Cemented Paste Backfill ◽  
Paste Backfill

Cemented paste backfill containing coal gangue and fly ash (CGFACPB) is an emerging backfill technique for coal mines that allows environmentally hazardous coal gangue and fly ash to be reused in the underground goaf. Meanwhile, CGFACPB can provide an efficient ground support and reduce the surface subsidence. Due to the difference of consolidation environment between the laboratory and the field, the mechanical properties of the cemented paste backfill vary significantly. In this paper, the core specimens were collected from an underground coal mine where the CGFACPB was used for coal mining, and the mechanical properties of the collected specimens were investigated. The cores were obtained from the underground coal mine, and then the standard cylinders or discs were prepared in laboratory. The uniaxial compressive strength (UCS), Young’s modulus, and Poisson’s ratio were determined by the compression tests, and the tensile strength was achieved by the Brazilian test. Then the internal friction angle and cohesion were calculated using the improved Mohr–Coulomb strength criterion. The results showed the development of UCS can be divided into four stages, and the final long-term stable value was about 5.1 MPa. The development of Young’s modulus had similar trend. Young’s modulus had a range from 550 MPa to 750 MPa and the mean value of 675 MPa. Poisson’s ratio gradually increased with the underground curing duration and eventually approached the stable value of 0.18. The failure type of compression samples was mainly single-sided shear failure. The development of tensile strength can be divided into two stages, and the stable value of the tensile strength was about 1.05 MPa. The development of cohesion can be divided into four stages, and the stable value was about 1.75 MPa. The stable value of the internal friction angle was about 25°. This study can provide significant references for not only the long-term stability evaluation of CGFACPB in the field but also the design of optimal recipe of the cemented paste backfill (CPB).

Research on Hole Making Mechanism of High Pressure Hydraulic Perforation

2014 ◽  
Vol 590 ◽  
pp. 96-100 ◽  
Author(s):  
Hai Cheng Li ◽  
Xu Jing Zhang ◽  
Fu Min Liang
Keyword(s):  
Finite Element ◽  
High Pressure ◽  
Stress Distribution ◽  
Tensile Stress ◽  
Water Jet ◽  
Rock Fragmentation ◽  
Rock Stress ◽  
Element Simulation ◽  
Pressure Water ◽  
High Pressure Water Jet

In this paper, we integrated use hydraulics, seepage flow mechanics, rock mechanics, and finite element simulation analysis and other methods to study the rock fragmentation mechanism of high pressure water jet. We make tensile stress - crack expansion comprehensive rock fragmentation model for the screw drilling of high pressure water jet. We make finite element simulation according to the mechanism of integrated model of high pressure water jet process, to analysis the internal rock stress distribution and external rock stress distribution of the fluid, and come to the reasonable number of high-pressure water jet nozzle hole. It is verified by the high pressure water jet breaking rock inside experiments of tensile stress - comprehensive rock fragmentation fracture expansion model, summarizes the law of high pressure water jet breaking rock, and we get to know reasonable drilling mode of the high pressure water jet is screw drilling with pitch of 120mm. At present there are two main types of the micro mechanism of the high pressure water jet. One is stress and tensile damage, because of the action produced by stress wave of the high pressure water jet impacting on rock, which mainly makes the tensile failure of rock; another one is crack expansion damage, under the effect of quasi static pressure radiation of water jet, the coupling effect between water shooting jet and rock pore skeleton, which make the rock pore, throat, and micro cracks expanding gradually, eventually the macro damage.

Fabrication of SiCp/Cu Composite by Powder Injection Molding

2011 ◽  
Vol 291-294 ◽  
pp. 721-724
Author(s):  
Jian Ming Yang ◽  
Hua Qiang Li ◽  
Hua Chen ◽  
Yi Qiang He ◽  
Li Chao Feng
Keyword(s):  
Tensile Strength ◽  
Injection Molding ◽  
Powder Injection Molding ◽  
Tensile Fracture ◽  
Powder Injection ◽  
Surface Microstructure ◽  
Excellent Performance ◽  
Sic Particles ◽  
Tensile Fractures

A SiCp/Cu composite with excellent performance is prepared by using the advanced powder injection molding technology. The microhardness and tensile strength of the composite are detected, and the surface microstructure and the tensile fractures are observed. The results show that SiC particles are uniformly distributed in Cu matrix and excellently bonded with the Cu matrix. With the increase of the SiC content, the microhardness of the composite is increased while the tensile strength is increased first and then decreased. A crackle source of the composite for tensile fracture mainly includes two kinds: cracking of the Cu matrix in vicinity of the SiC particles and debonding of an interface of the SiC particles and the Cu matrix.

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