Stress Distribution Of Rock Research Articles

Визначення параметрів окремо розташованих породних опор з компенсаційними порожнинами

Purpose: To determine the parameters of detached rock packs with compensating voids. Methodology: Analysis of technologies for the protection of development workings, based on the management of the stress-strain state of rocks around the workings, physical modeling using equivalent materials, numerical modeling by the finite element method, and methods of structural mechanics. Results: In the conditions of soft soil rocks the expediency of application of protection means based on management of a stress-strain condition in a surrounding massif and redirection of extrusion forces from a working has been substantiated. On the basis of analysis of the existing protection measures of the workings behind faces the prospects of use of protection technologies by means of construction of detached rock packs with limiting surfaces between which there are compensatory voids left, have been proved. To determine the parameters of such packs and voids between them in the conditions of soft soil rocks, a set of laboratory and numerical studies has been performed. According to their results, it has been established that to ensure the redirection of extrusion forces from the working it is necessary to build rock packs with limiting surfaces in the form of rectangular parallelepipeds with orientation of their greater side perpendicular to the longitudinal axis of production and trapezoidal prisms with their narrower orientation towards the working. Recommendations on the parameters of these structures and compensatory voids between them in the conditions of soft soil rocks have been formulated. Scientific novelty: On the basis of numerical modeling the regularities of stress distribution in rocks under detached rock packs of different shapes have been investigated, which allowed substantiating the parameters of the last and compensatory voids between them to ensure the stability of workings in the soft soil rocks. Practical significance: The expediency of application of technologies of protection of preparatory workings behind faces in the conditions of soft soil rocks by means of rock packs with limiting surfaces between which there are compensatory voids has been proved, and their parameters have been defined.

НАУКОВІ ПІДХОДИ ДО ВИЗНАЧЕННЯ ТЕРМІНУ “КРИТИЧНА ІНФРАСТРУКТУРА”

Purpose: scientific substantiation of the concept of “critical infrastructure” based on research of definitions of “infrastructure” and “critical” and comparison of definitions that are widely used in different countries. Methodology: analysis of the content of the concept of “critical infrastructure”, based on the content of the basic terms “infrastructure” and “critical”, analysis of the concept of “critical infrastructure” in laws and regulations of different countries and logical-determinative assessment of these concepts. Results: the general concept of “critical infrastructure” is substantiated – physical and virtual systems, objects and resources – the destruction, destruction or reduction of capacity of which will lead to significant threats to the country (region or city), its national security, life and health. A common understanding of this concept is important in the context of growing and diversifying threats and increasing the complexity of technical, information and social systems, when there is a growing need to protect the basic, ie critical parts of these systems, without which they can not function. Based on the analysis of existing concepts used in regulations and legislation of different countries, as well as scientific approaches of different authors, the main logical characteristics of this concept are identified, and based on the synthesis formed a generalized concept of “critical infrastructure”, which can be the basis for formulating derivatives such as social critical infrastructure, critical engineering infrastructure, etc. Scientific novelty: On the basis of numerical modeling the regularities of stress distribution in rocks under detached rock packs of different shapes have been investigated, which allowed substantiating the parameters of the last and compensatory voids between them to ensure the stability of workings in the soft soil rocks. Scientific novelty: on the basis of comparative analysis the characteristic features of the concept of “critical infrastructure” are singled out, a variable number of definitions of “critical” and “infrastructure” is analyzed, and a general definition of this concept is proposed, which provides a common understanding and can be used. Practical significance: the formulated definition of the concept of “critical infrastructure” will allow the unification of this concept in the scientific field, legislation and regulations. It will allow to formulate derivatives of this concept, in particular, transport, military, social, engineering infrastructure on uniform methodological approaches.

Analysis of Deformation of Circular Roadway Considering Effects of Intermediate Principal Stress and Dilatancy

Based on the unified strength theory and non-associated flow rule, with the consideration of the effects of intermediate principal stress and dilation characteristics, the analytical expressions of surrounding rock stress, displacement and plastic zone radius were obtained. Then the influences of the intermediate principal stresses and dilation angles on the surrounding rock stress, displacement and the plastic zone radius were analyzed by engineering example. The analysis shows that surrounding rock stress distribution and plastic zone radius have close relations with the intermediate principal stress. With the increase of the intermediate principal stress coefficient, the ultimate strength of surrounding rock increased, but the plastic zone radius shows a decreasing trend. The displacement of plastic zone is not only related to the intermediate principal stress coefficient, but also to the dilation angle. The displacement of plastic zone increased with the increase of dilation angle, and the displacement of plastic zone decreased with the increase of the intermediate principal stress coefficient.

Research on Distribution and Evolution Laws of Surrounding Rock Stress During the Island Panel Mining in Multiple Complex Stope

This paper was to explore distribution and evolution of surrounding rock stress as well as roadway deformation failure during the exploitation of working faces in complex stope. Here, distribution and evolution laws of surrounding rock stress and strata pressure behaviors in the complex island panels 1213(1) in a mine in Huainan Mine during early isolation, overhead mining, normal isolation and stopping in gob were analyzed by combining FLAC3D numerical simulation and field measurement. Results were shown that surrounding rock stress distribution along the strike direction and incline direction, abutment pressure peak value and position as well as surrounding rock deformation in the roadway were different in different mining stages. Different spatial stope layout (left and right gob, lower gob and upper gob) could influence the abutment pressure distribution on working faces, stress concentration range and surrounding rock deformation in roadway significantly. Therefore, professional analysis, reasonable design and safety mining should be performed in advance according to specific engineering geological conditions. Research conclusions could provide certain engineering references and guidance to stope arrangement, optimal design of mining roadway and mine pressure control.

Research on Failure Mechanism and Strengthening of Broken Roadway Affected by Upper Coal Pillar

The principal stress difference is introduced as a new evaluation index in order to better understand the failure mechanism of roadways affected by upper coal pillars and characterize failure of rock mass. Compared with traditional methods, it facilitates quantitative analysis. Moreover, we combine the semiplane theory and we obtain the stress distribution on the coal pillar’s bedrock and the strengthening control area from the “change point” position along a 21 m horizontal line. The influence of multiple stresses induced from mining on a roadway is analyzed. It is found that rock failure is most likely while mining the 051606 working face, followed by mining the 051604 working face, and the stress influence on the upper pillar has the lowest failure probability. In addition, based on the asymmetry of the surrounding rock stress distribution, this study proposes strengthening control technology of surrounding rock on the basis of a highly stressed bolting support and anchor cable, adding to the steel ladder beam, steel mesh, and shed support’s protective function to the roadway’s roof and ribs. Finally, through field observations, it is concluded that the roadway deformation is within the controllable range.

Mathematical model of rock stress under abrasive slurry jet impact based on contact mechanics

With development of water jet technology, abrasive water jet (AWJ) has become a new tool for cutting hard rock, which is widely used in stone processing, tunneling, and mining. Abrasive slurry jet (ASJ) is superior to AWJ in its ability and efficiency of rock cutting and breaking due to the addition of high-polymer. However, the stress field of rock impacted by ASJ directly affects the cutting and breaking efficiency, but there is no unified microscopic mechanism of rock failure under ASJ impact due to the uncertain contact type between the rock and the abrasive particles. In this paper, contact mechanics is used to establish a new mathematical model of rock stress under ASJ impact, which shows the rock stress distribution. Moreover, the mathematical model was solved numerically and presented in a rectangular coordinate system, from which the rock stress concentration area and failure type can be obtained. The results show that rock stress concentration appears at four areas (the center, edge, axis of particle indentation, and the edge of slurry jet), where rock is apt to be broken with axial compressive failure, radial tensile failure, shear failure, and radial tensile failure, respectively. Moreover, the rock stress caused by abrasive particle impact is much larger than that by slurry jet impact.

Optimal Rock Bolt Installation Design Based on 3D Rock Stress Distribution and Stereography Coupled Analysis

AbstractThe position determination for rock bolt support design based on rock stress distribution is important in ensuring full mobilization of rock bolt tensions during excavation process. The monitoring of the progressive rock stress variation in magnitude and orientation can play an important role in optimal installation of rock bolt. The aim of this paper is to determine the optimal positions for rock bolt installation by computing the progressive directional variation of rock stresses and plot the stress distribution in a two-dimensional stereographic projection to capture the stress transformation during excavation process. Finally, an algorithm based on stress transformation determination for optimal rock bolt installation is proposed.

Wave prefracturing of solid rocks under blasting

Considering features of wave prefracturing (microfailure) of rocks under blasting, the authors put forward a new investigation approach with the use of relations of dynamic elastic stress distribution in rocks and theory of cracks. The obtained relation to estimate prefracturing zone size in relatively solid rocks under confined explosion involves pressure of gases in explosion chamber, rock pressure, crack resistance of rocks, characteristic dimension of natural jointing (presence of defects) and deformation characteristics of rocks. It is shown that dimension of prefracturing zone in rocks depends both on natural and production factors and can differ by a few times.

Mechanism of rock breaking by pick assisted with water jet of different modes

In the rock breaking progress, the resistant force results in tools failure and the low cutting efficiency, thus, it is necessary to reduce the failure of tools and enhance the efficiency of cutting and drilling. In this paper, different configuration modes of water jet were presented to solve this issue. Moreover, the symmetrical pre-split finite element models for rock breaking by pick without water jet and picks assisted with different configuration modes of water jet were established to analyze the effect of different configuration modes on rock stress distribution and pick cutting forces. Finally, the experiments were conducted to validate the theory analysis. The results indicate that the cutting force decreasing rate of JCP is maximum all the time under the same conditions compared with the decreasing rate of JSP and JFP; and the numerical results were consistent with the numerical, which verifies the correctness of theory analysis.

Research on Hole Making Mechanism of High Pressure Hydraulic Perforation

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.

Rock Breaking by Conical Pick Assisted with High Pressure Water Jet

In the process of hard rock breaking, the conical pick bears great cutting force and wear, and the cutting efficiency is lower. Thus different combination ways of water jet and conical pick were proposed to solve this issue; for instance, water jet placed in the front of pick (JFP) and water jet through the center of pick (JCP) was researched by numerical simulation and experiments in this paper. First, the models of rock breaking were built based on SPH combined with finite element method. Then, the stress distribution of rock and the cut force of pick were analyzed when the rock broken by the conical pick assisted with the high pressure water jet. It indicates that the effect of the JCP on rock breaking is better than the JFP. At last, experiments about rock breaking with a conical pick and the JCP were conducted to verify the reliability of the simulation. It indicates that the rock breaking with the assistance of high pressure water jet cannot only reduce the pick force, but also increase the rock crushing volume.

Research on Mining Technological Parameters of 7<sup>#</sup> Thin Coal Seam in Liuquan Mine

Aimed at the specific geological conditions of 7# thin coal seam in Liuquan Mine, this paper used the methods of numerical calculation and theoretical analysis to determine the reasonable technological parameters of high-grade conventional mining face. The numerical simulation software of UDEC (Universal Distinct Element Code) was used to contrast and analyse the characteristics of surrounding rock stress distribution and overlying rock horizontal displacement under the condition of different length of coalface, then it was indicated that the surrounding rock deformation was less when length of coalface was 110 m which was advantageous for roof control; according to the conditions of roof and floor, the roof support strength was being calculated systematically to determine the row space of props being 700×1200 mm; the main equipments of coalface was assorted, and reasonable work manner in coalface and gob processing measure was put forward, which provided guidance for efficient mining in thin coal seam.

Research and Exploration on Combined Support Technology in Deep Soft-Rock Roadway

Because of the existence of high stress in the surrounding rock of deep roadway, the physical and mechanical properties of the surrounding rock to change, and the surrounding rock stress distribution is very different from the shallow, so the way of shallow roadway support is not suitable for deep roadway. Deep soft-rock roadway support is a complex systems engineering, it should consider the different geological conditions, roadway scope of application, construction technology conditions, construction period and the cost and other factors to determine the optimal combined support program, if the special geological conditions encountered in the construction, it should be timely to improve the supporting program to meet the construction safety and ensure the quality. This paper is based on the characteristics of deep roadway support, sums up the combined support form in the project, researches and analyzes the combined support technology, and explores how to use suitable combined support form in deep roadway.

Research about the Rationality of Neighborhood Tunnel Spacing

Analysis of the surrounding rock stress distribution of neighborhood tunnel by using numerical simulation. Based on Cullen-Moore Theory, build a mathematical model of 1st principal stress σ1, 2nd principal stress σ2, internal friction angle φ, and cohesion c, then, make a expression of tunnel spacing safety factor A. Analysis a real tunnel project and evaluate its surrounding rock stability with safety factor A as the index. Propose an analysis method of judging the rationality of tunnel spacing.

The Study of Stress Distribution Law of Roadway Surrounding Rock Heading Advancing Coal Face

In background of the geological engineering and the mining technical conditions of ZhangJi coal mine 17258 fully-mechanized face and rail roadway of 1724 (1) fully-mechanized face,by the field observation and computer numerical simulation studying the stress distribution law of roadway surrounding rock heading advancing coal face.Obtain the influence scope of the dynamic pressure along coal seam trend and tendency, the stress peaks position, perturbation boundary angle of dynamic pressure,and the surrounding rock stress distribution law of roadway excavating in the zone of the stress concentration and stress reduced area. Provides the theoretical foundation for roadway layout under similar conditions.

The Damage Theory Model on Fluid-Solid-Heat Coupling of Reservoir under Process Injection

Based on the study of double porous medium, the paper provides a new model of cylinder volume element plastic yielding, which assumes that the rock mass is compressible and obeys the D-P formula, and deformation, nucleation and growing of pores and fractures are induced by stress of injection pressure and temperature. The damage variable is defined by strain porosity, and then constitutional equation of double pore medium saturated liquid-solid is set up. Taking one well of Jilin Oil Field in China as a case, the damage variable, porosity and induced stress change laws of rock strain coupling with temperature-injection are studied. The results are acquired from numerical simulation of finite element software, including induced stresses of thermal field, water flood pressure, rock stress distribution rule, together with evolving regulations of stress, damage variable and strain porosity. The numerical computation results match well with the practical situation, which shows that there is obvious elastic and plastic damage characteristic during mass water flood recovery. The new model provides a new research method and theoretical base for changes of reservoir pores and fractures during water flood exploration.

Three Dimensional Numerical Approach to Splitting Failure of Rock Discs

The Brazilian splitting tests have been commonly and widely used as a standardized test method on disc or cylinder specimens to measure the indirect tensile strength of rocks in mining engineering and other rock engineering. In this paper, a novel numerical code, 3D Rock Failure Process Analysis code, was applied to implement the splitting tensile failure tests on rock discs. The influences of the heterogeneity on stress distribution in rock are also discussed and the splitting failure patterns of specimens subjected to Brazilian tests are simulated. The simulated splitting results of rock discs were found quite realistic, which indicate that the rock failure analysis method is applicable and practical for the study of rock disc splitting failure.

Fracture mechanics analysis of the North West Fault Block of the Prudhoe Bay Field

Fracture mechanics analyses using the boundary element program FROCK have been used to determine the changes in the stress directions and magnitudes caused by the major faults around the North West Fault Block (NWFB) of the Prudhoe Bay Field. These changes from the regional stresses can have important implications on the direction and magnitude of flow in the faults, the fractures, and the rock mass as a whole, and therefore impact production. The rock stress distribution is also very important in the design of drilling operations. The analyses show that the faults can considerably modify the stress directions and magnitudes in NWFB. Larger faults have larger influences on stress and have a larger zone of influence. For example, the Niakuk Fault, although most parts of which are far from NWFB, has considerable influence on the stresses in NWFB. Fault details can also have important effects on the stresses in the areas close to the faults. Even though the regional stresses are compressive, fault openings and small normal stresses on the fault surfaces can result from the interaction of fault sliding movements. These can cause increased conductivities of the fault segments being opened or stress-relieved. Stress direction predictions from the fracture mechanics and four wellbore breakout analyses have been compared. The differences in the predictions range from 5 to 33°.

Influence of the shape of an inclusion on the stress distribution in rock

Influence of the shape of an inclusion on the stress distribution in rock

軸圧を受けた岩石の応力分布の不均質性を定量化する試み

A stochastic model was used to quantify the heterogeneity of stress distribution in rocks subjected to uniaxial compression stress. In the model, the micro-fracturings are supposed to occur when local stress exceeds the average strength of the rock. The stress heterogeneity is measured by correlation distance in the autocorrelation function of stress distribution. The smaller the correlation distance, the larger the stress heterogeneity. The calculated results based on the model show that the m-value of an ensemble of acoustic emissions (i) increases with decrease of the correlation distance and (ii) decreases as the difference between applied stress and average strength of rock becomes large. In comparison with the experimental results, it is found that the correlation distance decreases as the axial stress approaches the fracture stress. This implies that the rock sample in dilatant state becomes heterogeneous with increase in axial stress.