Crack Formation Process Research Articles

Phase-field ductile fracture simulations of thermal cracking in additive manufacturing

We present a multiphysics phase-field fracture model for thermo-elasto-plastic solids in the context of finite deformation and apply it to simulate the hot cracking phenomenon during metal additive manufacturing. The model is derived in a thermodynamically consistent manner, with the intercoupling mechanisms among elastoplasticity, phase-field crack and heat transfer comprehensively considered. It involves particularly coupled parameters among these materials physics, e.g. plasticity-dependent degradation function and fracture toughness, damage-dependent yield surface and thermal properties, and temperature-dependent elastoplastic properties and fracture strength. The finite element implementation of the coupled phase-field model is benchmarked with simulation results of a tensile test of an I-shape specimen, encompassing elastoplasticity, hardening, necking, crack initiation and propagation, in contrast to the related experimental results. The validated model is further employed to simulate the multiphysics hot cracking phenomenon in additive manufacturing in the context of both the effective powder-bed model and the powder-resolved model thanks to prior non-isothermal phase-field powder-bed-fusion simulations. Simulation results reveal certain key features of the hot crack and its dependency on process parameters like beam power and scan speed, which are helpful for the fundamental understanding of crack formation mechanisms and process optimization.

Theoretical studies of the process of crack formation during rotational impact drilling

This article is devoted to the study of the process of crack formation, which are actively manifested during rotational impact drilling. The studies conducted during the writing of the article show that simultaneously with the destruction of the bottom of the well, another process occurs – the formation of many cracks in the angular (peripheral) zones of the bottom and on the walls of the well, going to a depth of 5-10 mm. These cracks remain in the form of a dense network in the walls of wells and in the core (during its selection), and the depth of the cracks increases with increasing impact energy. An attempt was made to explain the mechanism of cracking in the core during impact-rotational drilling from the standpoint of the theory of off-center impact. However, the study of cracking occurred when drilling wells on blocks of rocks. With the rotary-impact method of drilling deep horizontal wells, the types and distribution of loads in the near-well array will be different. This article presents technologies that increase the volume of production in depleted fields. During the calculations, the dependences of the impact force of the transmitted seal (rock) depending on its compliance are given. In addition, a graph of the dependence of changes in the impact force of the striker on the anvil on the impact time with different malleability of the anvil is constructed. The process of forming a horizontal well, which is drilled with a continuous face in a shock-rotational way using hydraulic impact machines, is considered. To study the process model, the results of solving the problem of stress distribution around the trunk array of a vertical well were considered.

Analysis of the Hydromechanical Behavior and Crack Formation Process in Expansive Soil Reinforced with Green Coconut Fibers

Analysis of the Hydromechanical Behavior and Crack Formation Process in Expansive Soil Reinforced with Green Coconut Fibers

Quantifying the sequential fine cracks of strain-hardening cementitious composites (SHCC): An automatic approach for temporal and spatial assessment

Strain-hardening cementitious composites (SHCC) are promising construction materials that enhance structural durability by forming multiple fine cracks under loading. Compared to conventional concrete, the cracks in SHCC are denser and tighter, making their quantification challenging. To thoroughly analyze and model the cracking behavior of SHCC, automatic algorithms with high accuracy are desired. In this paper, a workflow based on deep learning algorithms and 3D connectivity analysis for characterizing the crack formation and development process in SHCC under tensile loading is proposed. Temporal and spatial crack information, such as the crack number and individual crack width development during the loading process as well as the cracking strength distribution along the tensile specimens, can be obtained with minimal effort. The established workflow can provide more information for evaluating the overall cracking behavior of SHCC with high efficiency, to facilitate multiscale modeling and micromechanics-based design of the material.

ЕКСПЕРИМЕНТАЛЬНІ ДОСЛІДЖЕННЯ СЕРІЙНОЇ ДОРОЖНО-АЕРОДРОМНОЇ ЗАЛІЗОБЕТОННОЇ ПЛИТИ

The results of experimental studies of the load-bearing capacity and crack resistance of the serially produced road-airfield reinforced concrete slab PAG, manufactured at Velikodolinsky Reinforced Concrete Plant LLC by order of the Odessa State Academy of Construction and Architecture, are presented. In accordance with the regulatory documents in force in Ukraine, one of two possible loading schemes was considered ― with a load by a concentrated force applied on the cantilever part of the slab. The slab was tested on a specially made stand, which consists of four support posts connected in pairs by beams on which the slab rested. The load was applied along the width of the slab in steps ― 0.04 from the destructive load, along two concentrated vertical stripes. Each load stage ended with a five-minute hold, at the beginning and end of which readings were taken on the measuring instruments. All tests were carried out using two 30t jacks and a 50t dynamometer. The principle of operation of the jack was that its lower plane pressed on a two-level cross-beam system, and through it the load was distributed onto the slab. During testing, the applied load, deflections and deformations were recorded on the slabs. Dial indicators and deflectometers were used as measuring instruments. The process of crack formation on the surfaces of the slabs was observed using a Brinell tube in the places of the greatest opening of the cracks. As a result of the tests, the load-bearing capacity of the slab was 163.2 kN with a bending moment of 78.3 kNm. The load corresponding to the onset of cracking is 86.4 kN with a bending moment of 36.9 kNm. The maximum crack opening width was 1.0 mm. Based on the indicator readings, graphs of the dependence of relative deformation on load were constructed. Graphs of the dependence of deflections on load are constructed using data from two deflection meters. Before the first crack appears, the maximum deflection of the slab is 12.0% of the deflection recorded at the end of the tests.

Трещинообразование натуральной и модифицированной прессованием древесины березы повислой (Betula pendula Roth): эффект показателя внутреннего трения под влиянием внешних возмущений

Obtaining information about the presence of cracks in raw materials, blanks and wood products is neces-sary to make a decision on the purposes of its subsequent processing and operation. The method for diagnosing cracks in wood is based on measuring internal friction. For prepared samples of natural and modified wood, sawn from the stem part of drooping birch (Betula pendula Roth) trees growing in Khlevensky Forestry, Lipetsk region. (52.184130, 39.110463, ASL 157m), exposed to radial and tangential directions with ultrasound (frequency 24.5 kHz, exposure 0-20 minutes, step 5 minutes) and pulsed magnetic field (strength - 0.3 T, exposure 0-2 minutes, step 0.5 minutes). Next, the internal friction of the samples was studied on an experimental setup by measuring the logarithmic damping decrement based on free-bending vibrations. The absolute values of the dimensionless coefficient of internal friction Q-1, as the main structural parameter for samples of natural and modified wood, were obtained at a significance level of p=0.95: for humidity, in the presence of one crack, Q-1 decreased by 7.04% (D=0.08), in the presence of two cracks - by 8.4% (D=0.15), in the presence of three cracks - by 9.06% (D=0.15); for ultrasound in the presence of one crack Q-1 decreased by 7.17% (D=0.05), in the presence of two cracks - by 8.46% (D=0.05), in the presence of three cracks - by 9.12% (D=0.09); for a pulsed magnetic field in the presence of one crack Q-1 decreased by 7.14% (D=0.05), in the presence of two cracks - by 8.39% (D=0.09), in the presence of three cracks - by 9.02% (D=0.09). When testing the samples of natural wood and pressure-modified drooping birch (Betula pendula Roth) wood, we obtained an asymptotic equation was obtained for ap-proximating the dependence of the decrease in Q-1 on the number of cracks, with the approximation value R2=0.994. The study of the dependence of internal friction on the process of crack formation in various types of wood provides preparation for the next stage - the construction of a prototype system for non-destructive testing of defects.

Features of stabilization of soft soils at the base of emergency deformed buildings using finely powdered injection materials in low pressure mode

At present, the strengthening of the soil base is often performed by high-pressure injection - injection of a solution under pressure that exceeds the structural strength of the soil (hydraulic fracturing mode). High-pressure injection makes it possible to successfully solve various geotechnical problems, but it has a number of disadvantages, first of all, the uncertainty of the shape and size of injection bodies created in the soil mass, as well as the impossibility of predicting the final deformation and strength characteristics necessary for design. It should be noted that directly from the production of injection works in the uncontrolled hydraulic fracturing mode, unpredictable technological deformations (rise followed by uneven settlement) of the Objects are observed, the base of which is stabilized, as a result of which crack formation processes in above-ground structures and fragmentary destruction of load-bearing elements develop. The article considers the possibility of solving the problem of predictable increase in the mechanical properties of stabilized soils on the example of a pilot production site in the central region of St. Petersburg. The proposed method makes it possible to ensure the absence of technological deformations from the production of injection works by using the author's kinematic scheme for the production of works and the use of modern solutions based on fine binders in the impregnation mode with an element of soil microfracture, that is, in the mode of controlled hydraulic fracturing at a reduced injection pressure of the injection solution.

ANALYSIS OF THE MANIFESTATION OF CRACKS IN ROCKS DURING HYDRAULIC HAMMER DRILLING

This article is devoted to the study of the process of crack formation in rocks during hydraulic hammer drilling. Analysis of the manifestation of cracks in rocks during hydraulic percussion drilling is a key aspect of research aimed at the optimization and efficiency of this drilling method. The article presents a comprehensive analysis of the mechanisms of crack formation in rocks under the influence of hydraulic shock waves, identifying factors influencing their development and propagation. The work highlights the basic principles and mechanisms of hydraulic percussion drilling, and also analyzes the factors influencing the formation of cracks in rocks during this drilling method. In addition, various parameters such as water pressure, impact velocity, tool type and rock characteristics are considered and their influence on fracture formation. The paper presents numerical modeling and calculation methods used to analyze the factors influencing the formation of cracks during well drilling. Basic parameters are considered, such as well depth, type of drilling equipment used, physical and mechanical properties of the rock, drilling fluid pressure and others. Examples of numerical calculations and modeling are given, as well as an assessment of the influence of various factors on the formation of cracks in rock. The purpose of this article is to summarize current information on the formation of cracks during the hydraulic percussion drilling method. The scientific significance of this study lies in the possibility of predicting and controlling the formation of cracks during hydraulic drilling, which contributes to more efficient use of resources and improved drilling safety. The results obtained can be used in the practice of geological exploration and mining work to optimize drilling processes and improve the quality of mineral extraction. Understanding the processes of formation of cracks in rocks with this drilling method will allow optimizing its use, improving control over the process and ensuring more efficient and safe extraction of minerals from the bowels of the earth.

EXPERIMENTAL STUDIES OF SERIAL REINFORCED CONCRETE PAG SLAB WITH ADDITIONAL STEEL FIBER REINFORCEMENT

Thus, in laboratory conditions, experimental studies of the bearing capacity and crack resistance of a serial PAG plate with additional steel fiber reinforcement in the amount of 1% were carried out. In accordance with the regulatory documents in force in Ukraine, one of two possible load schemes was considered ― when loaded by a concentrated force applied to the cantilever part of the slab. The plate was tested on a specially made stand consisting of four support racks connected in pairs by beams on which the plate rested. The load was applied across the width of the slab in steps of 0.04 from the destructive load, in two concentrated vertical strips. Each level of load ended with a five-minute exposure, at the beginning and end of which the readings on the measuring devices were taken. All tests were carried out using two 30-ton jacks and a 50-ton dynamometer. The working principle of the jack consisted in the fact that its lower plane pressed on a two-level cross-beam system, and through it the load was distributed on the slab. In the process of testing the plates, the applied load, deflections and deformations were recorded. Clock-type indicators and protractors were used as measuring devices. The process of crack formation on the plate surfaces was observed with the help of a Brinell tube in the places of the largest crack opening. 
 As a result of the tests, the bearing capacity of the plate was 211.2 kN with a bending moment of 101.4 kNm. The load corresponding to the beginning of crack formation is equal to 96.0 kN at a bending moment of 46.1 kNm. The maximum width of crack opening was 0.25 mm. According to the readings of the indicators, graphs of the dependence of the relative deformation on the load were constructed. Graphs of the dependence of deflections on the load, constructed from the data of two deflection gauges. Before the appearance of the first crack, the maximum deflection of the plate is 17.0% of the deflection recorded at the end of the tests.

Investigation of crack recognition and spatio-temporal evolution pattern in coal samples damage

Understanding the evolution mechanism of cracks helps to evaluate the behavior and performance of rock masses and provides a theoretical basis for the mechanism of crack propagation and instability. For this purpose, a rock mechanics testing system and an acoustic emission monitoring system were used to conduct acoustic emission positioning experiments on coal samples under uniaxial compression. According to clustering theory, the distribution pattern of microcracks and the dynamic evolution process of multiple cracks were studied. Subsequently, the reasons for the change in the spatio-temporal entropy (H) and fractal dimension (D) of a single crack were revealed. The research results show that microcracks present a statistical equilibrium distribution, the Gaussian distribution model is applicable to cluster crack distribution patterns, and a machine learning method can effectively identify cracks. The fractal dimension reflects the spatial characteristics of three-dimensional elliptical cracks, and low-dimensional cluster cracks are more likely to develop into macroscopic cracks. The change of H is related to the formation process of cracks, and an abnormal H (sudden increase and sudden decrease) could provide precursor information for the instability of coal samples. This research provides a new method to study crack distributions and formations and shows the competitiveness of the method in evaluating the damage state of coal.

Cracking process in expansive soil with and without vegetation covers in dry and rainy seasons at field scale

ABSTRACT The presence of desiccation cracks in the soil alters its hydromechanical behavior, increasing the soil's water infiltration capacity, mobilizing the potential for expansion. This may affect the performance of the structural elements of the construction. This study aimed to evaluate the mechanics of expansion, contraction and cracking of the expansive soil of Paulista - Pernambuco, Brazil, through field trials, subject to wetting cycles and drying. The studied soil is a sandy silty clay of high compressibility with medium to very high expansion potential. The process of formation and propagation of cracks was analyzed using digital images and the monitoring of samples subjected to drying and wetting cycles. The indices of crack geometry increased with the advancement of desiccation but did not stabilize. During the wetting period, they tend to close. The pattern of cracks in the tests varied according to the presence or absence of vegetation. It was concluded that the vegetation cover has a significant influence on the standardization and the crack formation and propagation process.

Developments in Portland cement/GGBS binders for 3D printing applications: Material calibration and structural testing

The work presented in this paper forms part of a wider research programme being undertaken on the development of low-carbon cementitious mortars for 3D printing applications. Specifically, this paper investigates the potential of ground granulated blast-furnace slag (GGBS) as a partial replacement for Portland cement. Five mortar mixes with varying water/binder (w/b) ratios (0.35 to 0.45) were tested, and to investigate their pumpability and buildability, a series of wall-like specimens were printed using a custom-built 3D printer under a range of speeds of 2 to 4 m/min. Pumpability was found to be directly related to w/b ratio, whereas buildability was found to be dependent upon both test parameters. Mortar mixes with w/b ratios in the range 0.37 to 0.40 demonstrated promising pumpability and buildability characteristics when extruded at the optimum printing speed of 2.5 m/min. Moreover, to demonstrate the application of the optimised mix, an arch truss prototype was printed and subsequently tested to failure to provide insights into the structural behaviour of a 3D printed arch truss member. From the process of crack formation and accompanying analysis, it was found that although the development of tensile stresses in the 3D printed prototype was minimal (a direct result of the arch geometry), it still governed the overall member behaviour due to the presence of internal stresses induced by restrained shrinkage.

Study on the influence of relative vibration between tool and workpiece on plastic side flow

The mutual vibration between the tool and the workpiece not only affects the surface roughness value, but also the vibration energy has a very important influence on the mechanical properties and plastic deformation of the material. Based on the interaction mechanism between the tool and the workpiece surface, the three-dimensional plastic deformation in the third deformation zone is studied. The analytical relationship among vibration and plastic side flow is explored, and the method of restraining plastic side flow is put forward. The change mechanism of flow velocity of materials under the influence of vibration is analyzed. Through analysis, vibration makes the material soften, which leads to more obvious plastic side flow phenomenon. Reducing vibration can effectively inhibit plastic side flow phenomenon. Finally, the influence of relative vibration between tool and workpiece on the formation process of surface cracks of workpiece is studied, and the number of cracks per unit area can be well reduced by reducing the vibration. The research content of this paper can provide theoretical basis for improving the surface quality of ultra-precision turning of spherical/aspherical surfaces, and is of great significance to the processing of high-quality spherical/aspherical mirrors.

Evaluation of the application effect of the inclined TPCTs on an embankment with the shady-sunny slope effect in permafrost regions

As an efficient engineering technology, the inclined two-phase closed thermosyphons (ITPCTs) are extensively adopted in the Qinghai-Tibet Highway (QTH) to prevent permafrost degradation. However, cracks still appear on the bituminous pavement of the ITPCTs embankment, which threatens the traffic safety. It is necessary to evaluate the application effect of ITPCTs and analyze the process of crack formation. In this study, a coupled hydro-thermo-mechanical (HTM) model for the ITPCTs embankment is proposed, and the cooling effect and restraining function of the ITPCTs are numerically evaluated by comparison the ground temperature, water content distribution and deformation process of the ITPCTs embankment and an unprotected embankment (UE). Then, the cause for longitudinal crack on the ITPCTs embankment is revealed, and the initiation time and occurrence location of longitudinal crack are determined. Finally, the spatial-temporal development of longitudinal crack is analyzed. Additionally, based on the cause for longitudinal cracks, some comprehensive measures to prevent and treat cracks are suggested. This study can serve as a reference for the maintaining the ITPCTs embankment in the QTH and designing the Qinghai-Tibet Expressway in the near future.

Internal corrosion cracks evolution in reinforced magnesium oxychloride cement concrete

In view of the difficulty of identifying internal micro corrosion-induced cracks in concrete and the poor accuracy of quantitative analysis, which results in inaccurate results regarding the law of formation of internal cracks, reinforced magnesium oxychloride cement concrete (RMOCC) was subjected to a galvanostatic acceleration test, and X-CT technology was combined with the support vector machines (SVM) identification algorithm and grey-level co-occurrence matrix (GLCM) theory. Using the SVM algorithm and GLCM theory, the internal average crack width of concrete and the contrast, correlation, angular second moment (ASM) and inverse difference moment (IDM), which characterise the change in slice texture information, were used as degradation parameters. Using the average internal crack width and IDM as the degradation index, a reliability degradation competition failure analysis was conducted to study RMOCC's law of internal crack formation. The results showed that the SVM algorithm had a greater than 95% accuracy in recognising cracks. In the entire corrosion-induced crack formation process, IDM and the average internal crack width values were consistent with the normal distribution. Through reliability degradation competition failure analysis between IDM and the average crack width value, the average crack width calculated with SVM is more suitable for the degradation analysis of internal corrosion-induced cracks in RMOCC.

Progressive Failure Characteristics and Failure Symptoms of Straight-Walled Arched Sandstone Tunnels

In order to investigate the development process of crack formation in shallow-buried sandstone tunnel, biaxial compression tests were conducted on a similar model of the real straight-walled arched sandstone tunnel. The results indicate that the initial crack appeared at the arch line on both sides of the tunnel and propagated downwards, eventually leading to spalling of the rock mass on the surface of the tunnel, forming a V-shaped groove. Additionally, slab cracks were observed in the straight wall on the right side of the tunnel, which were approximately parallel to the vertical load. The failure characteristics of the tunnel were closely related to the fractal dimension of the crack geometry distribution. During the tunnel compaction and elastic deformation stage, the fractal dimension of the cracks in the tunnel surface increased linearly, while during the crack propagation stage, the fractal dimension increased gradually, with a sudden increase occurring just before the rock mass reached its peak load. The acoustic emission results revealed that AE ringing counts and amplitude were inactive during the first 4239 seconds of the test. And they only increased during the crack propagation stage. The continuous decrease of the b-value and the sudden increase of the fractal dimension of cracks can serve as a reliable precursor of tunnel failure.

Nanomodified Basalt Fiber Cement Composite with Bottom Ash

Directed control of the process of structure formation of a cement composite from modern positions must be carried out taking into account the synergistic effect of its components. In particular, the cement composite, when applied with pozzolanic additives and fiber reinforcement, is transformed into a more complex material with excellent performance. The aim of the article is to study the combined action of nanomodified basalt fiber (NBF) and bottom ash (BA) as structural elements of concrete. To achieve this aim, a number of tasks were performed, including the development of nanomodified-basalt-fiber–bottom-ash–cement concretes, as well as the study of their fresh, physical and mechanical properties (flowability, average density, compressive and flexural strength, elastic modulus and crack resistance) and durability characteristics (water, frost and abrasion resistance). A series of nanomodified basalt-fiber-reinforced concretes (from 0 to 7 wt.% NBF) were developed, in which the economical Portland cement CEM I 32.5 N was replaced by up to 45 wt.% mechanically activated bottom ash residue (400 m2/kg). An economical superplasticizer with a high water-reducing capacity (35%) made it possible to achieve uniform flowability of the mixes (slump 20–22 cm and slump flow 45–52 cm). The combined effect of BA and NBF provides control over the structure formation of cement materials, which ensures the redistribution of internal stresses from shrinkage deformations throughout the entire volume of the composite; under loading, the process of crack formation slows down, the stress concentration near structural defects decreases, and stresses are redistributed in the microstructure of the cement composite between its components. Perfect values of mechanical properties (compressive strength up to 59.2 MPa, flexural strength up to 17.8 MPa, elastic modulus up to 52.6 GPa, critical stress intensity factor 0.507 MPa m0.5) are explained by the complex action of the ash residue and nanomodified basalt fibers. A mix with 30 wt.% BA and 5 wt.% NBF is characterized by water resistance grade W18, frost resistance class F400 and abrasion resistance 0.59 g/cm2, which confirms the high wear resistance of the developed materials.

In situ high-temperature 3D imaging of the damage evolution in a SiC nuclear fuel cladding material

Silicon carbide (SiC)-based nuclear fission fuel rod cladding has been considered as one of the possible designs for accident tolerant fuels. It is in the form of a SiC fibre reinforced SiC matrix composite tube (SiCf-SiCm) with monolithic SiC outer and/or inner coating layers. This study focuses on the deformation and fracture processes in this material using in situ X-ray micro-computed tomography (XCT) at room temperature (RT) and 1200 °C in an inert gas environment in a C-ring compression loading configuration. Prior to testing, local properties and residual stresses were characterised using nanoindentation and Raman spectroscopy since they can impact the mechanical behaviour of the material. The 3D strain distribution, crack formation and propagation processes including the toughening mechanisms (e.g., crack deflection, micro-cracking, crack bridging and bifurcation) are investigated in the coating and underlying composites at RT and 1200 °C. There is no particular sequence which toughening mechanism occurs first – this is very different from the conventional toughening theory in ceramic-matrix composites under uniaxial tension loading. Indeed, no evidence of fibre pull-out or fibre fracture was observed in this SiCf-SiCm nuclear cladding material in the current C-ring compression configuration. The correlation between local measurements and bulk mechanical behaviour are discussed.

Combined effect on properties and durability performance of nanomodified basalt fiber blended with bottom ash-based cement concrete: ANOVA evaluation

A control of a cement composite structure formation from modern positions should be carried out taking into account the synergistic effect of its components. The goal of the article is to study the combined effect of nanomodified basalt fiber (NBF) and bottom ash (BA) as structural elements of concrete using a two-factor analysis of variance ANOVA. The tasks for achieving this goal are the development of nanomodified basalt fiber bottom ash-cement concretes, as well as the study of their fresh, physical and mechanical properties (slump, slump flow, average density, compressive and flexural strength, elastic modulus and crack resistance) and durability performances (water, frost, and abrasion resistance). Nanomodified basalt-fiber-reinforced concretes (from 0 to 7 wt % NBF) have been developed, in which the economical Portland cement CEM I 32.5 N is replaced by up to 45 wt % mechanically activated bottom ash (400 m2/kg). Achieving uniform flowability of the compositions (slump 20–22 cm and slump flow 45–52 cm) was carried out by varying the dosage of an economical superplasticizer with a high water-reducing ability (35%). The joint effect of the BA and NBF provides control over the structure formation of cement materials, which ensures the redistribution of internal stresses from shrinkage deformations throughout the entire volume of the composite; during loading, the process of crack formation is retarded, stress concentration near structural defects is reduced, and stresses are redistributed in the microstructure of the cement composite between its components.High values of mechanical properties (compressive strength up to 59.2 MPa, flexural strength up to 17.8 MPa, elastic modulus up to 52.6 GPa, limit stress intensity factor 0.507 MPa m0.5) are explained by the complex effect of bottom ash and nanomodified basalt fibers. For the composition with 30 wt % BA and 5 wt % NBF, W18 water resistance grade, F400 frost resistance grade, and the abrasion resistance of 0.59 g/cm2 were achieved, which characterizes the high durability of the developed materials.

ОБҐРУНТУВАННЯ ПАРАМЕТРІВ АНКЕРНОГО КРІПЛЕННЯ ПІДГОТОВЧИХ ВИРОБОК В УМОВАХ ІНТЕНСИВНИХ ВОДОПРИПЛИВІВ

Purpose. Improvement of the method of reducing water inflows into mine workings with using com-bined frame-roof bolting to ensure the stability of the mine workings, waterproofing and protection against the collapse of wet contour rocks inside the mine workings. Methods. When solving the problem of water filtration in deformed rock, the method of studying the state of a layered rock massif with a mine working in the presence of water-saturated layers in its vicinity, which was developed by the authors, as well as the finite element method, were used. Research results. As a result of the calculations, the stress values, the zones of inelastic defor-mations, the values of permeability coefficients, water pressure and water inflows have been obtained for the roadways supported with different number of roof bolts. It is shown that the number of roof bolts af-fects all these parameters around the roadway in the rock mass and in the water-saturated seam. If a larg-er number of roof bolts are installed, the processes of crack formation and, accordingly, rock fracturing are slower. After mining, if 3 or more roof bolts installed, intensity of water filtration process is minimal, but after 2-3 days water from the water-saturated seam begins to penetrate deep into the surrounding rocks. Roof bolting significantly reduces these processes, the using of a scheme with 5-9 roof bolts re-strains the movement of water and, most importantly, practically isolates the roadway from water-saturated rocks. Scientific novelty. For the first time, a numerical model has been created and the calculations have been completed for roadways supported with 1-9 roof bolts in conditions of intensive inflows over time from the moment of its building. Practical significance. Research and calculations make it possible to obtain a significant economic effect due to the setting of the optimal number of roof bolts and the reduction of the use of materials for supporting the roadway and, at the same time, to prevent water inflows and increase the stability of road-ways.