scholarly journals Shear Resistance of Rock Joint under Nonuniform Normal Stress

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Hang Lin ◽  
Hu Wang ◽  
Yifan Chen ◽  
Rihong Cao ◽  
Yixian Wang ◽  
...  
Keyword(s):  
Shear Strength ◽  
Stress Distribution ◽  
Normal Stress ◽  
Rock Joint ◽  
Distribution Patterns ◽  
Shear Resistance ◽  
Nonuniform Distribution ◽  
Rock Joints ◽  
Linear Superposition ◽  
Normal Stress Distribution

Many factors influence the shear resistance of rock joints. Among them, the above overburden load is the most important factor. The uneven thickness of the overburden causes the joints to be subjected to the nonuniform distribution load. While the peak shear strength shows nonlinear relationship with normal stress, linear superposition cannot be used to calculate the overall shear resistance of joint under nonuniform normal stress distribution. In this paper, the nonlinear shear strength model, JRC-JCS model, is applied to study the overall shear resistance of the joint under four nonuniform distribution patterns of normal stress. The results show that when the normal stress is distributed in a nonuniform way, the shear resistance provided by rock joint as a whole decreases with the increase of the normal stress distribution interval. Given the nonuniform distribution of normal stress along the joint, the shear resistance obtained by the Mohr-Coulomb linear model is overestimated. In order to give full play to the overall shear performance of the joint, the shear strength at different positions on the joint should be as close as possible. Then, the shear strength of joint parts can enter peak state condition simultaneously, at which time the shear strength is fully exerted.

Direct Measurement of the Contact Normal Stress Distribution between Two Smooth Joint Surfaces

2014 ◽  
Vol 638-640 ◽  
pp. 427-432
Author(s):  
Zon Yee Yang ◽  
Wei Chieh Chiu
Keyword(s):  
Shear Strength ◽  
Stress Distribution ◽  
Normal Stress ◽  
Contact Stress ◽  
Rock Joints ◽  
Wall Material ◽  
Normal Stress Distribution ◽  
Joint Surfaces ◽  
High Normal Stress ◽  
Distribution Behavior

The shear strength of rock joints is highly depended upon the failure mode of joint asperity. At lower normal stress slide-up of one asperity up over another mode, however at high normal stress the joint asperities are sheared off at the base. This research uses pressure measurement film to directly measure the contact normal stress between smooth joint surfaces. It demonstrates that the density of color impression is capable of capturing the normal stress distribution behavior. The contact normal stress distribution during shearing is changed. After shearing, the contact stress becomes large. This increase in contact normal stress is to fracture the joint wall material.

Stress in Bonded Adherends for Single Lap Joints

1996 ◽  
Vol 12 (03) ◽  
pp. 167-171
Author(s):  
G. Bezine ◽  
A. Roy ◽  
A. Vinet
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Numerical Model ◽  
Stress Distribution ◽  
Normal Stress ◽  
Lap Joints ◽  
Axial Loads ◽  
Normal Stress Distribution ◽  
Single Lap Joints ◽  
Element Technique

A finite-element technique is used to predict the shear stress and normal stress distribution in adherends for polycarbonate/polycarbonate single lap joints subjected to axial loads. Numerical and photoelastic results are compared so that a validation of the numerical model is obtained. The influences on stresses of the overlap length and the shape of the adherends are studied.

scholarly journals A temperature- and stress-controlled failure criterion for ice-filled permafrost rock joints

2018 ◽  
Vol 12 (10) ◽  
pp. 3333-3353 ◽  
Author(s):  
Philipp Mamot ◽  
Samuel Weber ◽  
Tanja Schröder ◽  
Michael Krautblatter
Keyword(s):  
Normal Stress ◽  
Failure Criterion ◽  
Slope Failure ◽  
Rock Slope ◽  
Shear Resistance ◽  
Stress Conditions ◽  
Rock Joints ◽  
Normal Stresses ◽  
Permafrost Rock ◽  
Limestone Sample

Abstract. Instability and failure of high mountain rock slopes have significantly increased since the 1990s coincident with climatic warming and are expected to rise further. Most of the observed failures in permafrost-affected rock walls are likely triggered by the mechanical destabilisation of warming bedrock permafrost including ice-filled joints. The failure of ice-filled rock joints has only been observed in a small number of experiments, often using concrete as a rock analogue. Here, we present a systematic study of the brittle shear failure of ice and rock–ice interfaces, simulating the accelerating phase of rock slope failure. For this, we performed 141 shearing experiments with rock–ice–rock “sandwich”' samples at constant strain rates (10−3 s−1) provoking ice fracturing, under normal stress conditions ranging from 100 to 800 kPa, representing 4–30 m of rock overburden, and at temperatures from −10 to −0.5 ∘C, typical for recent observed rock slope failures in alpine permafrost. To create close to natural but reproducible conditions, limestone sample surfaces were ground to international rock mechanical standard roughness. Acoustic emission (AE) was successfully applied to describe the fracturing behaviour, anticipating rock–ice failure as all failures are predated by an AE hit increase with peaks immediately prior to failure. We demonstrate that both the warming and unloading (i.e. reduced overburden) of ice-filled rock joints lead to a significant drop in shear resistance. With a temperature increase from −10 to −0.5 ∘C, the shear stress at failure reduces by 64 %–78 % for normal stresses of 100–400 kPa. At a given temperature, the shear resistance of rock–ice interfaces decreases with decreasing normal stress. This can lead to a self-enforced rock slope failure propagation: as soon as a first slab has detached, further slabs become unstable through progressive thermal propagation and possibly even faster by unloading. Here, we introduce a new Mohr–Coulomb failure criterion for ice-filled rock joints that is valid for joint surfaces, which we assume similar for all rock types, and which applies to temperatures from −8 to −0.5 ∘C and normal stresses from 100 to 400 kPa. It contains temperature-dependent friction and cohesion, which decrease by 12 % ∘C−1 and 10 % ∘C−1 respectively due to warming and it applies to temperature and stress conditions of more than 90 % of the recently documented accelerating failure phases in permafrost rock walls.

Normal stress distribution adjacent to optimum holes in composite plates

1994 ◽  
Vol 29 (4) ◽  
pp. 393-398 ◽  
Author(s):  
R. Ramesh Kumar ◽  
G. Venkateswara Rao ◽  
K.S. Suresh
Keyword(s):  
Stress Distribution ◽  
Normal Stress ◽  
Composite Plates ◽  
Normal Stress Distribution

Stresses in a Thick Plate With Axially Symmetric Loading

1965 ◽  
Vol 32 (2) ◽  
pp. 458-459 ◽  
Author(s):  
T. J. Lardner
Keyword(s):  
Stress Distribution ◽  
Normal Stress ◽  
Numerical Integration ◽  
Elastic Plate ◽  
Thick Plate ◽  
Axially Symmetric ◽  
Pressure Loading ◽  
Normal Stress Distribution ◽  
Symmetric Loading

The problem of the thick elastic plate with a symmetric circular pressure loading is considered. The normal stress distribution on the midplane and for two positions off the midplane is obtained by a numerical integration of the solutions. A comparison of the stress distribution on the midplane is made with previous results.

Normal stress distribution in highly concentrated suspensions undergoing squeeze flow

2013 ◽  
Vol 52 (2) ◽  
pp. 155-163 ◽  
Author(s):  
Mohsen Nikkhoo ◽  
Khosrow Khodabandehlou ◽  
LeAnne Brozovsky ◽  
Francis Gadala-Maria
Keyword(s):  
Stress Distribution ◽  
Normal Stress ◽  
Squeeze Flow ◽  
Concentrated Suspensions ◽  
Normal Stress Distribution

The Research of Pure Bending Flanged Beam’s Stress Distribution in Civil Engineering

2012 ◽  
Vol 568 ◽  
pp. 168-171
Author(s):  
Jian Ou Pan ◽  
Yu Jing Jia ◽  
Guang Zhen Cheng
Keyword(s):  
Stress Distribution ◽  
Normal Stress ◽  
Civil Engineering ◽  
Effective Means ◽  
Measurement Technology ◽  
Stress And Strain ◽  
Test Bed ◽  
Pure Bending ◽  
Normal Stress Distribution ◽  
Measuring Point

Experimental method is an important means to research the mechanical properties of materials in civil engineering. In this paper, first, analyzing the section of pure bending beam’s normal-stress distribution, drafting the measure scheme of flanged beam’s pure bending normal-stress, arranging measuring point in different place about the section of pure bending, adopting multi-function composite test-bed, static strain gauge and other testing instrument, by step loading, to finish the measure of each measuring points’ stress and strain, also, analysis and treatment for test data. According to the result of analysis and treatment, pointing out that measured stress and strain of pure bending beam is proportional to loading. The measured normal-stress distribution of the pure bend beam is uniform with theoretical analysis, which is satisfy the engineering demand. Knowing and mastering multipoint measurement technology and method is an effective means for the scientific research.

Observations by Evaluating the Uncertainty of Stress Distribution in Truss Structures Based on Probabilistic and Possibilistic Methods

2017 ◽  
Vol 2 (3) ◽  
Author(s):  
Sushan Li ◽  
Roland Platz
Keyword(s):  
Monte Carlo ◽  
Stress Distribution ◽  
Normal Stress ◽  
Direct Methods ◽  
Truss Structure ◽  
Truss Structures ◽  
Model Parameters ◽  
Normal Stress Distribution ◽  
Fuzzy Analysis ◽  
Input Parameters

Load-bearing mechanical structures like trusses face uncertainty in loading along with uncertainty in stress and strength, which are due to uncertainty in their development, production, and usage. According to the working hypothesis of the German Collaborative Research Center SFB 805, uncertainty occurs in processes that are not or only partial deterministic and can only be controlled in processes. The authors classify, compare, and evaluate four different direct methods to describe and evaluate the uncertainty of normal stress distribution in simple truss structures with one column, two columns, and three columns. The four methods are the direct Monte Carlo (DMC) simulation, the direct quasi-Monte Carlo (DQMC) simulation, the direct interval, and the direct fuzzy analysis with α-cuts, which are common methods for data uncertainty analysis. The DMC simulation and the DQMC simulation are categorized as probabilistic methods to evaluate the stochastic uncertainty. On the contrary, the direct interval and the direct fuzzy analysis with α-cuts are categorized as possibilistic methods to evaluate the nonstochastic uncertainty. Three different truss structures with increasing model complexity, a single-column, a two-column, and a three-column systems are chosen as reference systems in this study. Each truss structure is excited with a vertical external point load. The input parameters of the truss structures are the internal system properties such as geometry and material parameters, and the external properties such as magnitude and direction of load. The probabilistic and the possibilistic methods are applied to each truss structure to describe and evaluate its uncertainty in the developing phase. The DMC simulation and DQMC simulation are carried out with full or “direct” sample sets of model parameters such as geometry parameters and state parameters such as forces, and a sensitivity analysis is conducted to identify the influence of every model and state input parameter on the normal stress, which is the output variable of the truss structures. In parallel, the direct interval and the direct fuzzy analysis with α-cuts are carried out without altering and, therefore, they are direct approaches as well. The four direct methods are then compared based on the simulation results. The criteria of the comparison are the uncertainty in the deviation of the normal stress in one column of each truss structure due to varied model and state input parameters, the computational costs, as well as the implementation complexity of the applied methods.

scholarly journals Solution of the Boussinesq’s problem in evaluating ratio between shear stress and contact pressure

2020 ◽  
pp. 139-151
Author(s):  
Е.Г. Хитров ◽  
А.В. Андронов ◽  
Е.В. Нестерова
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Normal Stress ◽  
Contact Pressure ◽  
Stress Function ◽  
Average Pressure ◽  
Normal Stress Distribution ◽  
Contact Patch ◽  
Wide Range ◽  
Boussinesq’S Problem

Решение фундаментальной задачи Буссинеска широко используется в технических науках и позволяет эффективно решать широкий спектр задач науки о лесозаготовительном производстве. На его основе удается получить практически значимые результаты в области оценки распределения напряжений, возникающих в обрабатываемом материале под воздействием рабочего органа. Цель нашего исследования - проанализировать результаты расчетов и установить соотношение максимального значения касательного напряжения и среднего значения давления по пятну контакта рабочего органа с обрабатываемом материалом. Теоретическую основу работы составляют уравнения распределения нормальных и касательных напряжений, возникающих в упругом полупространстве при вдавливании в него жесткого клина. В результате анализа теоретических расчетов показано, что характер затухания нормального напряжения по глубине деформируемого массива материала с высокой точностью аппроксимируется квадратичной функцией (на основе полученной приближенной функции выполнено сопоставление среднего давления по пятну контакта индентора с массивом и нормального напряжения по глубине массива). При этом, как показали результаты расчетов, функция распространения касательного напряжения в деформируемом массиве имеет экстремум. Выполнено сопоставление полученных данных по значению экстремума функции касательного напряжения со значением приближенной функции нормального напряжения на границе контакта индентора сдеформируемым массивом. В результате показано, что максимальное по модулю касательное напряжение составляет 11-12% среднего контактного давления. Расчеты проведены при варьировании коэффициента Пуассона материала массива, установленное соотношение остается практически неизменным. Solution of fundamental Boussinesq’s problem is widely used in technical sciences and allows effectively solving a wide range of problems in forestry science. On its basis, it is possible to obtain practically significant results in the field of assessing the distribution of stresses arising in processed material under the influence of a working body. The purpose of our study is to analyze the results of calculations and establish the ratio of the maximum value of the shear stress and the average pressure over the contact patch of the working body with the material being processed. The theoretical basis of the work is formed by the equations for the distribution of normal and tangential stresses arising in an elastic half-space when a rigid cone is pressed into it. As a result of the analysis of the results of theoretical calculations, it was shown that the character of the normal stress distribution over the depth of the deformed massif of material is approximated with high accuracy by a quadratic function (based on the obtained approximate function, the average pressure over the contact patch of the indenter with the massif and the normal stress over the depth of the massif were compared). In this case, as shown by the results of calculations, the function of the shear stress distribution in the deformed massif has the extremum. Comparison of the obtained data on the value of the extremum of the shear stress function with the value of the approximate normal stress function at the interface of the indenter contact with the deformable mass is performed. As a result, it is shown that the maximum shear stress in absolute value is 11-12% of the average contact pressure. The calculations were carried out with varying Poisson's ratio of the massif material; the established ratio remains practically unchanged.

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