Roof Deformation Research Articles

Comparative Histopathological Analysis of Nasal Osteotomy Techniques in a Rabbit Model.

Objective: Nasal osteotomy is a crucial step in rhinoplasty, explicitly addressing the open roof deformity in nasal bones. This study aimed to assess and compare the recovery patterns associated with 4 distinct osteotomy techniques in a rabbit model. Materials and Methods: Twenty white New Zealand rabbits weighing 2.5 to 3.0 kg were included in the study. Median osteotomies were performed on the left side using piezosurgery and on the right side using an oscillating micro-saw. Additionally, internal osteotomy was executed on the right side and external osteotomy on the left side, both performed with a chisel across all rabbits. Ten rabbits were sacrificed on the 7th day, while the remaining 10 were sacrificed on the 15th day for subsequent histological examination. The granulation tissue formation (GTF), vascularization, inflammation, collagen fibril content, osteotomy gap width, and new bone formation were evaluated in hematoxylin and eosin and Masson's trichrome-stained sections. Results: On the 7th day, piezosurgery demonstrated statistically-significant advantages in terms of GTF, neovascularization, and collagen fibril quantity when compared to the oscillating micro-saw (P < .05). Furthermore, a statistically-significant difference was observed among the groups concerning the distribution of connective tissue organization between the 7th and 15th days (P < .05). Conclusions: This study's findings unequivocally establish that bone healing after osteotomy with piezosurgery surpasses that achieved with an oscillating micro-saw in this rabbit model.

Open-Roof Deformity: How to Avoid, How to Cure?

Objectives: Of all the face surgeries, rhinoplasty is known to be the most difficult. The aim of this paper is to review open-roof deformity. Methods: PubMed, EBSCO, UpToDate, Proquest Central at Kırıkkale University, and Google and Google Scholar were used in the literature review. The search was performed with the keywords "open roof deformity," "rhinoplasty," "fillers" between 2024 and 1980. Results: Rhinoplasty is a surgery that requires a combination of art and science, unlike other procedures that may have challenging anatomic access, requiring an excessive amount of physical strength, or a long operating period that causes surgeon fatigue. It is common for people undergoing primary rhinoplasty to have their hump removed, which can lead to open-roof deformity. Lateral osteotomies and the use of grafts are crucial in the prevention of open-roof abnormalities. It is common practice to perform lateral osteotomies to seal this space. However, lateral osteotomy becomes tricky when the patient's bony vault is small. Another well-known option is to shape and replace the hump or to use a spreader graft, flap, sliced cartilage, or some combination of these. HA filler can also be administered to achieve the same effect as a spreader graft. Along the length of the dorsum on both sides, HA is injected retrogradely. Conclusion: If there are dorsal irregularities after surgery or if there is a need to fix the look of nasal bridge, this therapy can help.

Predictive model for the instability of flexible formwork concrete wall in secondary mining of non-pillar coal mining

The secondary mining movement in non-pillar coal extraction causes significant overrun damage to flexible formwork concrete walls, leading to extensive deformation of roadway roof and bottom plates. This adversely affects working face efficiency and safety. The engineering context focuses on the non-pillar gob-side retaining walls in the 1315 working face of Zhaozhuang Coal Mine and the 23107 working face of Xiegou Coal Mine. Through on-site investigation, numerical simulation, theoretical analysis, and testing, we explore the stress migration law and destabilizing mechanism of the flexible formwork concrete wall influenced by the secondary mining movement of the coal-free pillar along the hollow wall. The research results showed that: (1) During the mining back process, the concrete wall formed with flexible formwork may experience stress concentration, leading to excessive damage and compromising mining safety. (2) Developing a predictive stress model for the concrete wall with flexible formwork is essential. If the stress surpasses the ultimate compressive strength during mining back, reinforcement becomes necessary.3) The length of damage overrun in the flexible formwork concrete wall exhibits two distinct stages as the distance back to mining increases. The first stage shows nearly linear growth, while the second stage indicates a decreasing growth rate, ultimately stabilizing. The application of Z6 concrete reinforcing agent effectively strengthens the flexible formwork concrete wall.

Optimization of a coal mine roof characterization model using machine learning

Predicting areas of increased propensity for roof deformation is crucial for the proactive management of geotechnical risk in underground coal mines. Current practices rely largely on assessing rock mass strength or characterization indices in isolation. Validation of applied ground support systems typically, and in part, comprises a review of observed deformation and analysis of extensometer data from adjacent previously mined areas. This information is seldom routinely assessed relative to the rock mass strength or characterization data. Typically, roof deformation is a response to several combining factors such as mining-induced stress, roof lithology, rock mass strength, and roadway geometry. Therefore, it is optimal to develop an approach to integrate these factors to quantify their relative significance to causing roof deformation, with the goal of establishing a reliable quantitative model for predicting roof deformation.This paper provides a case study in machine learning using Artificial Neural Network (ANN) and geophysical log data information from an underground coal mine located in the Bowen Basin (Australia), whereby a suite of parameters is considered pertinent to excavation stability. This machine learning predictive model analyses key geotechnical parameters including field and mining-induced stress, rock mass strength, clay/shale content, and strata monitoring data to identify strata hazards. Finally, the classification model can indicate the risk of roof displacement and observed roof deformation as communicated through a contoured ‘geotechnical hazard map’. This hazard map can assist site engineers understand roof conditions in underground coal mining and thus put in place operational mitigation processes to reduce geotechnical risk on mining. This could potentially improve the identification of high-risk areas and inform future bolting requirements to maintain a safe working environment and minimise production interruptions.

Research on Key Parameters for Relieving Pressure on Roofs of Deep Mine Cutting and Retaining Roadways

Scientific and reasonable roof-cutting parameters are key to ensuring pressure relief of the retained roadway roof. This manuscript takes the 7135 working face of Qidong Coal Mine as the engineering background and uses theoretical analysis, numerical and on-site measurement methods to study the quantitative relationship and pressure relief effect between different roof-cutting parameters of GERRC. We established a fracture criterion based on the tensile strength of the main roof of the uncut joint along the cutting line. We analyzed the quantitative relationship between different main roof thickness, cutting height, cutting angle, and the main roof tensile stress of the uncut joint. We found that within a small range of cutting angles, as the cutting angle decreases, the tensile stress on the main roof of the uncut joint increases. When the cutting angle is 0, the main roof tensile stress of the uncut joint reaches its maximum. As the cutting height increases, the limitation of the cutting angle on the cutting height becomes smaller. Numerical simulation was conducted to study the distribution patterns of maximum and minimum principal stresses along the direction of the roadway roof during the retention period under different roof-cutting heights and angles. Based on this, the optimal unloading effect of the roadway roof and the minimum concentration of mining stress were obtained at a roof-cutting height of 9 m and a roof-cutting angle of 80°. Through on-site measurement of the stress on the reinforcement anchor cable during the retention period, the deformation of the sinking roadway roof, and the pressure relief control effect of the retained roadway roof, the pressure relief effect and scientific rationality of the design of the cutting height and cutting angle were verified.

Quantitative Research on Roof Deformation and Temporary Support Stiffness in Deep-Mine Gob-Side Entry Retaining by Roof Cutting

The important technical process to ensure the success of gob-side entry retaining by roof cutting (GERRC) was the advanced pre-splitting blasting to cut off the mechanical connection between the roadway and working face roof. The whole-cycle roof structure evolution and stress characteristics of GERRC were analyzed. The factors affecting the roof deformation of GERRC were analyzed, and the quantitative relationship between the roof deformation of GERRC and the support stiffness was determined. The results showed that the temporary support stiffness was higher, the support position to the side of the roof cutting was closer, and the roof subsidence deformation of GERRC was smaller. It is proposed to use a single support mass with a high stiffness to control the deformation of the roof, but it also made the support mass and roof elastic potential energy aggregate. To fully utilize the matching of the support stiffness and roof subsidence, improve the stability, and control the subsidence deformation of the roof in GERRC, double-row stacking supports were adopted in the inclination of GERRC, which were used to increase the stiffness of the support system.

Research on the mechanism and control of roof deformation in gob-side entry retaining of close-distance coal seams

Multiple mining operations in close-distance coal seams (CDCSs) can reduce the integrity and bearing capacity of the surrounding rock, leading to roof fracturing and widespread subsidence in gob-side entry retaining (GER). This highlights the critical need for research on roof control technology. For this purpose, adopting the panel of the Xinchazhuang Coal Mine (the distance between two coal seams is 7.3 m) as the engineering background, a theoretical model of GER of CDCSs was established on the basis of the surrounding rock structure and roof rock movement characteristics, and the roof failure deformation mechanism was examined. The roof failure deformation encompasses two parts: rotational sinking of roof rock blocks and roof separation deformation. To achieve roof control, a strategy involving optimized roof cutting and higher preload cables was suggested. The impacts of key roof control parameters on roadway deformation were examined and compared by numerical simulation studies. The findings showed that optimized roof cutting resulted in a 21.1 % reduction in the roof stress, whereas the use of roof cables with higher preload levels resulted in a 55.1 % decrease in roadway deformation, effectively mitigating rotational sinking and roof separation deformation. The field tests demonstrated that the optimized scheme facilitated roof integrity preservation, and the maximum deformation of the roof reached 98 mm, a decrease of 68.5 % on average from that in the original scheme. These research results could provide a reference for roof support in CDCSs roadways under similar geological conditions.

Geomechanical Analysis of the Main Roof Deformation in Room-and-Pillar Ore Mining Systems in Relation to Real Induced Seismicity

Rockbursts represent one of the most serious and severe natural hazards emerging in underground copper mines within the Legnica–Glogow Copper District (LGCD) in Poland. The contributing factor determining the scale of this event is mining-induced seismicity of the rock strata. Extensive expertise of the copper mining practitioners clearly indicates that high-energy tremors are the consequence of tectonic disturbances or can be attributed to stress/strain behaviour within the burst-prone roof strata. Apparently, seismic activity is a triggering factor; hence, attempts are made by mine operators to mitigate and control that risk. Underlying the effective rockburst control strategy is a reliable seismicity forecast, taking into account the causes of the registered phenomena. The paper summarises the geomechanics analyses aimed to verify the actual seismic and rockburst hazard levels in one of the panels within the copper mine Rudna (LGCD). Two traverses were designated at the face range and comparative analyses were conducted to establish correlations between the locations of epicentres of registered tremors and anomaly zones obtained via analytical modelling of changes in stress/strain behaviours within the rock strata. The main objective of this study was to evaluate the likelihood of activating carbonate/anhydrite layers within the main roof over the excavation being mined, with an aim to verify the potential causes and conditions which might have triggered the registered high-energy events. Special attention is given to two seismic events giving rise to rockbursts in mine workings. Results seem to confirm the adequacy and effectiveness of solutions provided by mechanics of deformable bodies in the context of forecasting the scale and risk of dynamic phenomena and selecting the appropriate mitigation and control measures in copper mines employing the room-and-pillar mining system.

Correction: Study on Roof Deformation and Failure Law of Close Distance Coal Seams Mining Based on Digital Image Correlation

Correction: Study on Roof Deformation and Failure Law of Close Distance Coal Seams Mining Based on Digital Image Correlation

Study on Reinforcing Anchor Cable Support in Overreach Section of Deep Roadway

With the increasing depth of coal mining, the conditions of deep working face are becoming more and more complex, the stability of surrounding rock of roadway is getting worse and worse, and the problem of deep roadway support is becoming more and more prominent. In this paper, the 24100 working face of Pingdingshan No.11 Coal Mine is taken as the engineering background. In view of the problems of roof crushing and deformation and more net pockets in the return airway affected by the mining of the working face, the grouting anchor cable reinforcement and support technology in the advance section of the deep mining roadway is proposed, and the feasibility of the support effect is verified by numerical simulation. The results show that the influence range of the advance abutment pressure of the air roadway is about 60 m, and the reinforcement support strength required for the roof of the roadway is 50.6 kN/m2. The grouting anchor cable reinforcement support technology system of the return air roadway can control the deformation of the surrounding rock of the roadway and achieve safe and efficient mining.

Effect of connection and grouting level on mechanical behavior of pipe roof

ABSTRACT Pipe roof support suffers from engineering defects such as connection and insufficient grouting in tunnel engineering. To analyze the influence of connection and grouting level on the mechanical behavior of pipe roof support during tunnel construction, a series of pure bending tests were conducted to measure the mechanical property of pipe roof, and quantitatively analyze the influence of the connection and grouting level on the bearing capacity and bending stiffness of the pipe roof. In addition, the double shear mechanical analysis model of pipe roof based on the Timoshenko beam theory and the Pasternak elastic foundation theory was established by considering the shear deformation of pipe roof, the supporting effect of surrounding rock of tunnel face and the delayed effect of shotcrete for primary support. Then, the solution methods for pipe roof deflection and internal force were derived based on this model. Based on an engineering case, the deflection and internal force distribution, as well as the effect of connection and grouting levels on the pipe roof were discussed. Corresponding construction suggestions were proposed and had achieved good results in the case. This research can provide reference for the design and construction of pipe roof.

Study on Roof Deformation and Failure Law of Close Distance Coal Seams Mining Based on Digital Image Correlation

Study on Roof Deformation and Failure Law of Close Distance Coal Seams Mining Based on Digital Image Correlation

Optimization of inclined coal seam tunnel section angle and anchor angle based on response surface method

The mining of inclined coal seams is often accompanied by problems such as difficult to control deformation of the tunnel roof and failure of anchor bolts. Taking the transportation channel of Jinping Coal Industry 1071-1 in Shanxi Xiangkuang Mine as the background, FLAC3D numerical simulation software was used, and the method of response surface experimental design and data analysis was used to systematically study the effects of the anchor installation angle and the roof inclination angle of the tunnel section on different inclination angles. Influence of the surrounding rock stability of coal seam roadways. On this basis, a multi-index tunnel support design evaluation method based on the response surface method was proposed, and the actual support plan was optimized and industrial tests were carried out based on the actual on-site support plan. The research results show that: in terms of inclined coal seam support, the degree of influence on the tunnel stability is in the following order: anchor installation angle &gt; tunnel section roof inclination angle &gt; coal seam inclination angle; the optimized support design obtained through the proposed technology The method has good application effect and can improve the stability of the roadway during the mining of the working face. It also proves the effectiveness of this technology and provides new ideas for the design of anchor support of inclined coal seam roadways and the optimization of roadway sections.

Local Instability and Deformation Control of Steel Roof of Factory Building in a Smart City

Abstract The traditional control methods of instability and deformation of steel structure neglect the analysis of its natural vibration characteristics, which lead to the poor effect of hysteretic vibration of steel structure nodes, and the stability optimization of steel structure is not ideal. Therefore, a new method to control the local instability and deformation of the steel roof is proposed. According to the steel structure composition of the upper door rigid frame and the connection mode of the frame beam and column, the roof steel structure characteristics of the workshop are analyzed. Multi-order natural frequency method is used to obtain the cumulative modal mass contribution rate of steel structure and analyze the natural vibration characteristics of steel structure. Based on the characteristics of natural vibration and element transfer matrix, the local instability control method of roof steel structure is designed. Simulation of strong vibration, using space analysis of tall-building with wall-elements (SATWE) software analysis of strong vibration under elastic load state, to obtain the external deformation of steel structure, under simulation of vibration deformation control model. Taking a chemical plant as an example, a finite element model was established to simulate the vibration wave, and the numerical simulation results of plastic deformation resistance of steel structure were analyzed. The experimental results show that the proposed method can effectively enhance the stability of steel structure and reduce its deformation degree.

Influence on the roof stability of EMU induced by welding deformation

The EMU roof with a thin plate structure is prone to buckling deformation during welding, which will affect its stability. Due to the complex structure, large size, and many types of welded joints, it is an urgent problem to solve the influence of different joint shapes on welding deformation and buckling stability in one model. Based on the inherent strain-temperature loading method, the inherent strain data of four kinds of local joint butt, lap, fillet, and plug welding were accurately obtained through joint welding deformation verification. Then the welding deformation simulation and buckling stability analysis were conducted. The results indicate that plug welding will have minimal impact on roof deformation. The roof buckling deformation cannot occur under the original and 1.2 times heat input conditions are selected within the range of the actual given heat source parameters. Under the 1.5 times heat input condition, the roof buckling deformation occurs. The results provide technical support for the selection of the welding process and the roof stability study of the EMU.

An exploration of improving the stability of mining roadways constructed in soft rock by roof cutting and stress transfer: A case study

In the confinement of traditional supports, reinforced supports are often used to control the deformation of roadways constructed in soft rock. Due to the failure to weaken the factors that induce deformation at the source, the roadway remains damaged after the restoration period. To this end, taking inspiration from roof cutting and pressure relief concepts, the protection mechanism of stress transfer in mining roadways constructed in soft rock of longwall remaining coal pillars was studied in the context of a typical coal mine. Unlike the technical scheme of gob-side entry retaining, no components are added in this study. The roof cutting and coal mining progress are consistent to ensure the integrity of the roadway in front of the longwall coal mining face (LCMF). The effect of the roof-cutting parameter on the roadway is studied via numerical simulations, and the optimal parameters are subsequently applied to similar material simulation experiments. It was found that roof cutting relieved the mechanical connection between the gob roof and the roadway roof, and the high-stress area was transferred from the roadway roof to the front of the LCMF. Roof cutting diminished the abutment stress in the surrounding rock in the area of intense dynamic pressure in front of the LCMF (average reduction of 12.57 %), which effectively improved the stability of the roadway. The roof cutting impaired the traction effect of the roadway roof deformation behind the LCMF on the strata ahead and effectively reduced the roadway deformation (27.3 % reduction) and coal pillar deformation (15.7 % reduction). On-site practice has demonstrated the effectiveness of this research, and the results of this research provide a new idea for preventing the destruction of roadways constructed in soft rock.

Experimental and numerical assessment for the roof-contacted filling effect of expansive backfill

The effect of roof-contacted filling is a significant factor that affects the ground pressure management in the filling mining method. The expansive backfill is developed to solve the problem of the difficulties of roof-contacted filling in the open stopes with subsequent filling mining method, as well as actively supporting the surrounding rock masses by expanding its own volume and generating certain pre-stress to the roof. This paper focuses on analyzing the mechanical effects of roof-contacted filling with expansive backfill using a simulation test. Subsequently, the results of the simulation test were validated through theoretical analysis and numerical simulation. The results showed that: (1) The roof of the roof-contacted unfilling (RCU) mining room and the roof of the roof-contacted filling with ordinary backfill (RCO) mining room were both under downward stress whereas the roof of the roof-contacted filling with expansive backfill (RCE) mining room was supported by upward stress. (2) The RCU mining room led to a stress concentration in the roof and pillar, whereas the RCO mining room relieved the stress concentration in the roof and pillar. The RCE mining room did not only relieve the stress concentration in the roof and pillar, but also provide support to the roof and pillar. (3) The expansion stress generated by the self-expansion of the expansive backfill played a direct supporting role to the roof and the upper part of the pillar, and produced a positive Poisson effect to the lower filling body, which in turn provided support to the middle and lower part of the pillar. (4) Compared to RCU and RUO, the RCE enables the filling body to change from passive bearing to active support of the roof and pillar. This transition allowed more effective limitation of roof and pillar deformation while working in coordination with them to improve stress distribution within the mining room. As a result, the stability of the mining room was maintained, and the effect of roof-contacted operations was significantly enhanced.

FEATURES OF RISK DETERMINATION AND CONTROL OF THE UNDERGROUND FACILITIES STABILITY LOSS UNDER CONDITIONS OF ROCKS PROPERTIES VARIATION

Problem statement. Modern geotechnical production or an underground structure used as a military-industrial facility must meet the requirements of international risk management standards, which form the basis of safe and effective management. Implementation of effective risk management improves the quality of decision making, and has a positive impact on the benefit of the enterprises and society as a whole. The purpose of the article. To improve the method of risks’ determining for the mining stability loss and other underground structures, taking into acount the variability of the physical and mechanical properties of rocks. Methods. The use of a systematic approach in analytical studies of literary sources, systematization of modern approaches and methods in determining risks in the life safety system, processing by statistical methods, and the use of probability theory. Research results. Based on the results of field studies of the underground mining of the Yubileynaya mine at the Pershotravenskoye Mining Structural Division of PuAT DTEK Pavlogradugol, graphs of roof deformations were constructed, displacements were determined, dependencies were obtained, and the risks of underground mining destruction were identified. Scientific novelty. For the first time, the use of the parameters’ scatter by their standard deviation in identifying the risk of stability loss for underground mining is proposed. Practical value. A methodology for identifying and predicting geomechanical parameters for a risk-oriented system for monitoring the stability of the rock mass while ensuring safety when using developments as military-industrial complexes is proposed.

Study of the Roof Deformation Characteristics of Roadway Excavation Face and Unsupported Roof Distance

In order to address the issue of slow excavation speed caused by various factors affecting the stability of the roof in the excavation face and the unreasonable distance of the unsupported roof, a mechanical model of the roof in the excavation face area is established. This model is based on the superposition method in the material mechanics. The immediate roof deflection curve equation and the maximum unsupported roof distance discriminant formula of the heading head are derived. The allowable deflection is used as the discriminant method of the maximum unsupported roof distance. The calculation method of the key parameters in the formula is obtained and compared with the existing maximum unsupported roof distance calculation formula. Using the single-variable sensitivity analysis method and the bivariate interaction analysis method, we determine the key factors affecting the deformation of the roof in the excavation face and their interaction relationships. The results indicate that among the 10 factors affecting the deformation of the roof in the temporary support area of the excavation face, there are 3 key factors. Under unchanged geological and mechanical conditions, the deformation of the roof primarily depends on the length of the temporary support area and the temporary support load. To provide a practical example, we calculate the maximum unsupported roof distance of 30304 tailgate in the Yanghuopan Coal Mine to be 3.4 m. Numerical simulation and field monitoring results confirm that the deformation of the roof in the excavation face is minimal, and the stability of the rock is good.

Mechanism and control of deformation in gob-side entry with thick and hard roof strata

Deformation of gob-side entries has always been a critical concern for ensuring stability in longwall coal mines. This paper addresses the significant deformation and support challenges that arise in thick and hard roof longwall faces (THRLF) due to dynamic pressure. The study aims to elucidate the characteristics and mechanisms of deformation during the retreat of the longwall face. The research findings indicated that the primary cause of deformation was the combination of advanced abutment stress resulting from longwall face mining and the movement of the lateral roof over the chain pillar. To mitigate this issue, we propose a deformation control method known as cutting off the lateral roof (COLR) over the chain pillar. Simulation results demonstrate a significant reduction in roof stress and deformation of the gob-side entry after implementing the lateral roof-cutting technique. These findings provide valuable guidance for effectively managing deformation in gob-side entries, particularly when dealing with thick and hard roof strata.