scholarly journals Investigation of Separation Non-Persistent Faults in Fracture Mechanism of Rock Bridge

2016 ◽  
Vol 2 (7) ◽  
pp. 348-357 ◽  
Author(s):  
Nasim Nohekhan Hokmabadi ◽  
Vahab Sarfarazi ◽  
Mohamadreza Moshrefifar
Keyword(s):  
Failure Mechanism ◽  
Shear Failure ◽  
Heterogeneous Material ◽  
Failure Pattern ◽  
Test Machine ◽  
Shear Load ◽  
Horizontal Edge ◽  
Rock Bridge ◽  
Uniaxial Test ◽  
Two Sides

Rock mass is a heterogeneous material included joints, fractures and faults. The necessity of rock mechanics studies in conducting constructional issues has become important due to the increase in constructional works and the expansion of the structure’s dimension and especially creating underground spaces in rock masses. Faults are the most important discontinuous fractures in the earth's crust in which the two sides of the fracture have moved relative to each other. The purpose of this research is that if the non-persistent faults were situated adjacent to each other, how would be the shear failure mechanism of Rock Bridge surrounded between the faults. For this purpose, physical model consisting two horizontal edge faults and a surrounded angled fault was built; angularity of the central fault varies from 0° to 60° with increasing the 30°. The central fault places in 3 different positions. Along the lateral faults, 1.5 cm vertically far from the edge faults and 3 cm vertically far from the edge faults. All samples tested by uniaxial test machine so that shear load was distributed in the specimens due to special geometry of specimen. The results show that the failure pattern was mostly influenced by configuration of central joint, while the shear strength was linked to the failure pattern and failure mechanism.

Shear Failure of Rock Under Compression

1965 ◽  
Vol 5 (02) ◽  
pp. 167-176 ◽  
Author(s):  
William C. Maurer
Keyword(s):  
Shear Strength ◽  
Failure Mechanism ◽  
Shear Failure ◽  
Heterogeneous Material ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Axial Pressure ◽  
New Concepts ◽  
External Pressures ◽  
Inclined Planes

Introduction It is difficult to produce tensile stresses under the high compressive stresses present in the earth; therefore, in deep drilling and geological faulting, shear failure predominates. This shear failure mechanism is complicated because rock is a heterogeneous material containing pore spaces, microfractures, elastic discontinuities and other imperfections. A study of shear failure of rock under pressure has been made to obtain a better understanding of this complex mechanism. A machine has been developed and used to measure the shear strength of rock and friction along sheared surfaces. This machine has certain advantages over the compression test-shear properties can be measured under low normal stresses and shear stress and normal stress can be varied independently. The first part of this paper is a description of shear failure of rock under pressure. The role of shear strength and friction along fracture surfaces in the shear failure mechanism will be discussed. The second part consists of a description of the shear machine and a discussion of the shear strength and friction data obtained using this machine. It will be shown that shear strength depends upon the size of the stressed zone, and that friction does not increase linearly with contact pressure as usually assumed. Attempts are made to relate some of the new concepts to tectonic failure and to drilling. SHEAR FAILURE IN ROCK TRIAXIAL TESTS The shear failure mechanism is illustrated by the triaxial test shown in Fig. 1. In this test, a cylindrical rock specimen is subjected to a confining pressure, pc, and an axial pressure, pa. These external pressures produce normal o and shear r stresses on inclined planes within the specimen equal to (1) (2) where theta is the angle between the specimen axis and a normal to the inclined plane. Fig. 2 shows how triaxial specimens deform as the axial pressure is increased. SPEJ P. 167ˆ

Numerical Analysis of Joint Rock Shear Properties Considering Joint Geometrical Characters

2010 ◽  
Vol 29-32 ◽  
pp. 149-154
Author(s):  
Qiang Zhang ◽  
Xiu Run Ge ◽  
Shui Lin Wang
Keyword(s):  
Shear Failure ◽  
Process Analysis ◽  
Failure Process ◽  
Shear Stiffness ◽  
Failure Pattern ◽  
Shear Load ◽  
Strength Evolution ◽  
Rock Failure Process ◽  
Weak Interlayer ◽  
Joint Rock

The purpose of this paper is to study the shear behavior of rock specimens containing joints with various distribution forms. Two sets of specimens are simulated by the rock failure process analysis code (RFPA2D). The friction-sliding failure pattern occurs with the lower undulation angle specimen, and the failure pattern turns to be tensile-shear failure mode gradually with the increase of undulation angle. The specimen possesses the highest peak shear load when the undulation angle is about 30º. And joint rock shear character also deteriorates with the increase of weak interlayer thickness. In the intermittent joint model, the unified connection ratio specimen’s peak shear load increases with rock bridge amount, and the multi-joint mode is beneficial to keep rock mass shear stiffness. This study comes to meaningful results to the expansion of joint rock strength evolution law with various joint distribution forms.

scholarly journals Strengthening of RCC Beams in Shear by Using SBR Polymer-Modified Ferrocement Jacketing Technique

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Rajinder Ghai ◽  
Prem Pal Bansal ◽  
Maneek Kumar
Keyword(s):  
Carrying Capacity ◽  
Shear Failure ◽  
Ultimate Load ◽  
Load Test ◽  
Wire Mesh ◽  
Styrene Butadiene Rubber ◽  
Shear Load ◽  
Butadiene Rubber ◽  
Load Carrying Capacity ◽  
Load Carrying

There is a common phenomenon of shear failure in RCC beams, especially in old buildings and bridges. Any possible strengthening of such beams is needed to be explored that could strengthen and make them fit for serviceable conditions. The present research has been made to determine the performance of predamaged beams strengthened with three-layered wire mesh polymer-modified ferrocement (PMF) with 15% styrene-butadiene-rubber latex (SBR) polymer. Forty-eight shear-designed and shear-deficient real-size beams were used in this experimental work. Ultimate shear load-carrying capacity of control beams was found at two different shear-span (a/d) ratios 1 and 3. The sets of remaining beams were loaded with different predetermined damage levels of 45%, 75%, and 95% of the ultimate load values and then strengthened with 20 mm thick PMF. The strengthened beams were then again tested for ultimate load-carrying capacity by conducting the shear load test at a/d = 1 and 3. As a result, the PMF-strengthened beams showed restoration and enhancement of ultimate shear load-carrying capacity by 5.90% to 12.03%. The ductility of strengthened beams was improved, and hence, the corresponding deflections were prolonged. On the other hand, the cracking pattern of PMF-strengthened beams was also improved remarkably.

scholarly journals Buckling Failure Mechanism of a Rock Dam Foundation Fractured by Gentle Through-Going and Steep Structural Discontinuities

2020 ◽  
Vol 12 (13) ◽  
pp. 5426
Author(s):  
Donghui Chen ◽  
Huie Chen ◽  
Wen Zhang ◽  
Chun Tan ◽  
Zhifa Ma ◽  
...  
Keyword(s):  
Numerical Method ◽  
Failure Mechanism ◽  
Shear Failure ◽  
Distinct Element ◽  
Mechanism Analysis ◽  
Rock Masses ◽  
Dam Foundation ◽  
Deformation Features ◽  
Universal Distinct Element Code ◽  
Distinct Element Code

The failure mechanism analysis of dam foundations is key for designing hydropower stations. This study analyses the rock masses in a sluice section, which is an important part of the main dam of the Datengxia Hydropower Station currently built in China. The stability of the sluice rock masses is predominantly affected by gentle through-going soft interlayers and steep structural fractures. Its foundation failure mechanism is investigated by means of a numerical method, i.e., Universal Distinct Element Code (UDEC) and the geomechanical model method. The modeling principle and process, and results for the rock dam foundation are introduced and generated by using the abovementioned two methods. The results indicate that the failure mechanism of the foundation rock masses, as characterized by gentle through-going and steep structural discontinuities, is not a conventional type of shear failure mechanism but a buckling one. This type of failure mechanism is verified by analyzing the deformation features resulting from the overloading of both methods and strength reduction of the numerical method.

scholarly journals Strength and Failure Mechanism of Composite-Steel Adhesive Bond Single Lap Joints

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Kai Wei ◽  
Yiwei Chen ◽  
Maojun Li ◽  
Xujing Yang
Keyword(s):  
Failure Mechanism ◽  
Shear Failure ◽  
Failure Load ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Adhesive Failure ◽  
Interface Failure ◽  
Element Analysis ◽  
Single Lap Joints ◽  
Structural Adhesive

Carbon fiber-reinforced plastics- (CFRP-) steel single lap joints with regard to tensile loading with two levels of adhesives and four levels of overlap lengths were experimentally analyzed and numerically simulated. Both joint strength and failure mechanism were found to be highly dependent on adhesive type and overlap length. Joints with 7779 structural adhesive were more ductile and produced about 2-3 kN higher failure load than MA830 structural adhesive. Failure load with the two adhesives increased about 147 N and 176 N, respectively, with increasing 1 mm of the overlap length. Cohesion failure was observed in both types of adhesive joints. As the overlap length increased, interface failure appeared solely on the edge of the overlap in 7779 adhesive joints. Finite element analysis (FEA) results revealed that peel and shear stress distributions were nonuniform, which were less severe as overlap length increased. Severe stress concentration was observed on the overlap edge, and shear failure of the adhesive was the main reason for the adhesive failure.

scholarly journals An Experimental Study on Shear Failure Mechanism of RC Interior Beam-Column Joints

1997 ◽  
Vol 8 (2) ◽  
pp. 39-49
Author(s):  
Yasuaki Goto ◽  
Osamu Joh ◽  
Takuji Shibata
Keyword(s):  
Experimental Study ◽  
Failure Mechanism ◽  
Shear Failure

Open Uniaxial Test Machine (OpenUTM): Part 1 — A Low-Cost Electrohydraulic Test Frame for Additive Manufacturing Part Qualification

2018 ◽  
Author(s):  
John C. Steuben ◽  
Athanasios P. Iliopoulos ◽  
John G. Michopoulos
Keyword(s):  
Additive Manufacturing ◽  
Low Cost ◽  
Test Machine ◽  
Mechanical Stiffness ◽  
Uniaxial Test ◽  
Bill Of Materials ◽  
Test Frame ◽  
Force Displacement

A wide variety of scientific and engineering activities require the use of testing machines in order to acquire data regarding the response of materials subjected to mechanical loads. This is particularly applicable to the domain of Additive Manufacturing (AM), where mechanical qualification is essential. Such machinery should be capable of applying loads at required levels and exhibit high mechanical stiffness. Accurate force, displacement, and strain measurements are also required. As a consequence, such testing machines are typically very costly. In the present paper we introduce the Open Uniaxial Test Machine (OpenUTM) project, aimed at providing a low-cost (less than $2500.00) material testing hardware/software framework. This paper will focus on the engineering design and hardware aspects of the OpenUTM project, with particular attention paid to the use of an electrohydraulic actuator (EHA) to provide test loads. A full bill of materials and drawings package is provided, in order to enable the use of the OpenUTM framework by research groups with minimal machine tooling. We introduce several case studies demonstrating the successful use of the OpenUTM frame in AM research efforts, including the testing and characterization of AM polymers and ceramics. We conclude with discussion of the software aspects of the OpenUTM framework, which will be elaborated upon in a follow-up paper (part two). We also present a series of potential avenues towards the improvement of the OpenUTM frame in future hardware iterations.

scholarly journals Failure Characteristics and Mechanism of Multiface Slopes under Earthquake Load Based on PFC Method

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Tao Yang ◽  
Yunkang Rao ◽  
Huailin Chen ◽  
Bing Yang ◽  
Jiangrong Hou ◽  
...  
Keyword(s):  
Moisture Content ◽  
Failure Mechanism ◽  
Failure Modes ◽  
Shear Failure ◽  
Shaking Table ◽  
Tensile Failure ◽  
Particle Flow Code ◽  
Shear Cracks ◽  
Local Shear ◽  
Shear Slip

Understanding the failure mechanism and failure modes of multiface slopes in the Wenchuan earthquake can provide a scientific guideline for the slope seismic design. In this paper, the two-dimensional particle flow code (PFC2D) and shaking table tests are used to study the failure mechanism of multiface slopes. The results show that the failure modes of slopes with different moisture content are different under seismic loads. The failure modes of slopes with the moisture content of 5%, 8%, and 12% are shattering-shallow slip, tension-shear slip, and shattering-collapse slip, respectively. The failure mechanism of slopes with different water content is different. In the initial stage of vibration, the slope with 5% moisture content produces tensile cracks on the upper surface of the slope; local shear slip occurs at the foot of the slope and develops rapidly; however, a tensile failure finally occurs. In the slope with 8% moisture content, local shear cracks first develop and then are connected into the slip plane, leading to the formation of the unstable slope. A fracture network first forms in the slope with 12% moisture content under the shear action; uneven dislocation then occurs in the slope during vibration; the whole instability failure finally occurs. In the case of low moisture content, the tensile crack plays a leading role in the failure of the slope. But the influence of shear failure becomes greater with the increase of the moisture content.

Research on Erosion of Metal Materials for High Pressure Pipelines

2012 ◽  
Vol 482-484 ◽  
pp. 1592-1595 ◽  
Author(s):  
Ji Xin Zhang ◽  
Jian Chun Fan ◽  
Yong Jin Xie ◽  
Han Chuan Wu
Keyword(s):  
High Pressure ◽  
Failure Mechanism ◽  
Wear Behavior ◽  
Petroleum Industry ◽  
Erosive Wear ◽  
Solid Particles ◽  
Test Machine ◽  
Material Loss ◽  
Metal Materials ◽  
Multiphase Fluid

Erosion phenomenon is quite common in petroleum industry, as one of the main mechanisms of material degradation, occurs frequently on high-pressure pipelines in hydraulic fracturing operation. With the increasing of operation times, the erosion and corrosion defects on the inner surface of the pipeline, would lead to serious material loss and equipment failure. In this paper a new type of test machine was developed to simulate the erosive wear behavior of metal materials caused by the multiphase fluid such as fracturing fluid, and study the erosion failure mechanism by various metal erosion influencing factors including the velocity of multiphase flow, solid particles of fracturing proppant and impact angles, etc. The erosion-wear experiments on 20CrNiMo steels used in high-pressure pipelines is described in detail. Finally, the microcosmic surface testing was also used to analyze the erosion failure mechanism of metal materials for high pressure pipelines.

scholarly journals Face Stability Analysis of Shield Tunnels in Homogeneous Soil Overlaid by Multilayered Cohesive-Frictional Soils

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Kaihang Han ◽  
Chengping Zhang ◽  
Wei Li ◽  
Caixia Guo
Keyword(s):  
Failure Mechanism ◽  
Shear Failure ◽  
Three Dimensional ◽  
Earth Pressure ◽  
Support Pressure ◽  
Tunnel Face ◽  
Arch Effect ◽  
Theory Approximation ◽  
Homogeneous Soil ◽  
Frictional Soils

In order to better interpret failure features of the failure of soil in front of tunnel face, a new three-dimensional failure mechanism is proposed to analyze the limit support pressure of the tunnel face in multilayered cohesive-frictional soils. The new failure mechanism is composed of two truncated cones that represent the shear failure band and a distributed force acting on the truncated cones that represents the pressure arch effect. By introducing the concept of Terzaghi earth pressure theory, approximation of limit support pressures is calculated using the limit analysis methods. Then the limit support pressures obtained from the new failure mechanism and the existing approaches are compared, which show that the results obtained from the new mechanism in this paper provide relatively satisfactory results.

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