scholarly journals A study on the geometric effects of a concrete filling body in remaining roadways with fully mechanised caving

2021 ◽  
Vol 18 (5) ◽  
pp. 681-690
Author(s):  
Minglei Zhang ◽  
Yue Yang ◽  
Linsheng Gao
Keyword(s):  
Bearing Capacity ◽  
Surrounding Rock ◽  
Control Effect ◽  
Reinforcement Scheme ◽  
Geometric Effect ◽  
Deformation Control ◽  
Rock Stability ◽  
Coal Deformation ◽  
Concrete Filling ◽  
Geometric Effects

Abstract To address the problem of the concrete filling body (CFB) force failing to reach test strength in remaining roadways, the weakening effects due to aspect ratio and dimensional parameters on the actual CFB strength were investigated in this study. The geometric effects of CFB (including hoop and size effects) as well as the geometric effect coefficient determination method were analysed. Through laboratory tests and PFC numerical simulations, the hoop and size effect coefficients of the CFB in the Gaohe Coal Mine were studied. Furthermore, the calculation equations of actual strength and bearing capacity of the CFB were derived. Regarding the filling body failure and coal deformation in the remaining roadway located at the No. W1319 working face, the actual bearing capacity of CFB and surrounding rock stability during secondary exploitation were theoretically studied. The investigation suggests the adoption of a grouting reinforcement scheme for surrounding rock. The field applications performed have demonstrated that the deformation control effect in the remaining-roadway surrounding rock was effectively improved during second mining and the filling body beside the roadway suffered no additional damage. Studying the geometric effect of CFB can provide some theoretical guidance and industrial significance to accurately identify the filling body strength and reduce the failure risk of surrounding rock in remaining roadways.

scholarly journals Study on the Instability Characteristics and Bolt Support in Deep Mining Roadways Based on the Surrounding Rock Stability Index: Example of Pansan Coal Mine

2020 ◽  
Vol 2020 ◽  
pp. 1-16 ◽  
Author(s):  
Jucai Chang ◽  
Kai He ◽  
Zhiqiang Yin ◽  
Wanfeng Li ◽  
Shihui Li ◽  
...  
Keyword(s):  
Coal Mine ◽  
Stability Index ◽  
Surrounding Rock ◽  
Full Length ◽  
Control Effect ◽  
Support Design ◽  
Rock Stability ◽  
Working Face ◽  
The Stability ◽  
Bolt Support

In view of the influence of mining stress on the stability of the surrounding rock of inclined roof mining roadways in deep mines, the surrounding rock stability index is defined and solved based on the rock strength criterion and the stress distribution. The mining roadway of the 17102(3) working face of the Pansan Coal Mine is used as the engineering background and example. The surrounding rock’ stabilities under the conditions of no support and bolt support are analyzed according to the surrounding rock’s stability index and the deformation data. The results show that the areas of low wall and high wall instability are 1.68 m2 and 2.12 m2, respectively, and the low wall is more stable than the high wall; the areas of the roof and floor instability are 0.33 m2 and 0.35 m2, respectively, and the roof and floor are more stable than the two sides. During mining, the area of instability greatly increases at first, then decreases to 0, and reaches a maximum value at the peak of the abutment pressure. The stability of the surrounding rock decreases first and then increases. Compared with the end anchoring bolt support, the full-length anchoring bolt support reduces the area of instability to a greater extent, and the full-length anchoring bolt support effect is better. The surrounding rock in the end anchoring zone and the full-length anchoring zone began to deform significantly at 200 m and 150 m from the working face, respectively. This indicates that the control effect of the full-length anchoring bolt support is better and verifies the rationality of the surrounding rock stability index to describe the instability characteristics. This research method can provide a theoretical reference for analysis of the stability characteristics and support design of different cross-section roadways.

scholarly journals Study on Surrounding Rock-Bearing Structure and Associated Control Mechanism of Deep Soft Rock Roadway Under Dynamic Pressure

2019 ◽  
Vol 11 (7) ◽  
pp. 1892 ◽  
Author(s):  
Dongdong Qin ◽  
Xufeng Wang ◽  
Dongsheng Zhang ◽  
Xuyang Chen
Keyword(s):  
Dynamic Pressure ◽  
Soft Rock ◽  
Friction Angle ◽  
Surrounding Rock ◽  
Control Effect ◽  
Pressure Relief ◽  
Reinforcement Scheme ◽  
Soft Rock Roadway ◽  
Bearing Structure ◽  
Rock Roadway

Providing support for deep soft rock roadways under dynamic pressure is a major technical challenge. In this study, the distribution characteristics of surrounding rock-bearing structure of such roadways were systematically examined using theoretical analysis and numerical simulation. Based on the control effect of different support methods on the surrounding rock-bearing structure; a reinforcement scheme for deep dynamic soft rock roadway was proposed and applied. The results indicate that: (1) by increasing the supporting strength of the internal bearing structure, cohesion, and internal friction angle of the surrounding rock, and by reducing the influence of mining, making the external bearing structure close to the roadway and reducing the thickness of the bearing structure, can improve the bearing capacity of the shallow surrounding rock in the roadway; (2) under the conditions of dynamic load and creep of the surrounding rock; the deformation of the rock increases significantly; external bearing structure is far away from the roadway, and thickness of the bearing structure increases; anchor cable support and floor pressure relief effect better control over the roof and the roadside deformation and floor heave, respectively; and the thickness of the corresponding external bearing structure is reduced by 30.84% and 41.50%, respectively; and (3) based on the application, the zonal reinforcement scheme of “fix cable to shed, floor pressure relief, deep-shallow composite grouting” is proposed and put into practice, with good results. The results of this study can provide theoretical support and reference for the determination of supporting parameters in deep roadways.

scholarly journals Monitoring and support optimization analysis of surrounding rock pressure and initial supporting stress in deep-buried soft rock tunnel

2020 ◽  
Vol 36 (4) ◽  
Author(s):  
Q. Liu ◽  
R. Li ◽  
W. Tian ◽  
Y. Wang ◽  
X. Li
Keyword(s):  
Rock Pressure ◽  
Soft Rock ◽  
Northwest China ◽  
Surrounding Rock ◽  
Steel Frame ◽  
Control Effect ◽  
Measuring Point ◽  
Deformation Control ◽  
Surrounding Rock Pressure ◽  
Rock Tunnel

Attempting at the problems of surrounding rock pressure and initial supporting stress of deep-buried soft rock tunnel, a soft rock highway tunnel project in Northwest China was monitored on-site for surrounding rock deformation, surrounding rock pressure, initial stress and other items.Discuss the deformation laws and stress characteristics of surrounding rock and steel arch at different construction stages, and compare and analyze the deformation control effect of surrounding rock with different initial lining thickness, different initial elastic modulus and different anchor length through numerical simulation.The results show that the excavation stage of the upper step is a stage where the pressure and deformation of the surrounding rock increase rapidly. The steel arch support is mainly compressed, and the average stress can reach more than 50% of the peak value within 5 days. The stress is mostly higher than the measuring point of the lower step. The initial steel frame support of the upper step and the middle step bears a greater load. The excavation of the upper middle step should be "passed quickly and supported in time", and the construction should adopt The “letting first,then resisting” method appropriately increases the reserved deformation of the surrounding rock to relieve the support stress of the primary steel frame. When the deformation of the surrounding rock and the growth rate of the surrounding rock pressure slow down, the secondary lining can be applied in advance. The research results can provide reference and reference for the design and construction of similar tunnel projects.

The Comparative Study on the Impact of Tunnel Excavation with Footage Different CRD to Testability of Surrounding Rock

2011 ◽  
Vol 243-249 ◽  
pp. 3417-3422
Author(s):  
Lin Po Shi ◽  
Bin Song Jiang ◽  
Yao Qiang Zhao
Keyword(s):  
Plastic Zone ◽  
Formation Control ◽  
Plastic Zone Size ◽  
Surrounding Rock ◽  
Zone Size ◽  
Control Effect ◽  
Tunnel Excavation ◽  
Rock Stability ◽  
The Comparative Study ◽  
The Impact

This article used Geotechnical Engineering General Software FLAC3D to simulate the tunnel CRD method under 1.5m, 2.0m, 2.5 m, 3.0 m footage separately and analysis the influence to the tunnel surrounding rock stability in the different footage construction. This paper selected a real tunnel project as the research object and analysis comparatively the rule and characteristic of various methods of tunnel surrounding rock displacement, stress distribution and the plastic zone size through simulated computing the different footage construction. The results show that,Ⅰ.Considered from the surrounding rock stress control that the 1.5m footage adjacent formation stress adjustment effect is best, next is 2.0m, 2.5 m, 3.0 m;Ⅱ.Considered from the plastic zone size that the 1.5m footage control effect is best, next is in turn 2.0m, 2.5 m, 3.0 m;ⅢConsidered from the surrounding rock displacement control that 1.5 meter footage adjacent formation control effect is best, but 2.0 meter, 2.5 meters and 3.0 meter phase differences are not big.

scholarly journals Supporting Technology Research in Deep Well Based on Modified Terzaghi Formula

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Wen-qing Peng ◽  
Wei-jun Wang ◽  
Chao Yuan
Keyword(s):  
Bearing Capacity ◽  
Difficult Problem ◽  
Surrounding Rock ◽  
Engineering Practice ◽  
Strength Criteria ◽  
Type Steel ◽  
Deep Well ◽  
Rock Stability ◽  
Floor Heave ◽  
Modified Formula

In order to solve the difficult problem of supporting roadway with large cross section and broken surrounding rock, the large-section inclined shaft of Pingdingshan Coal Mine is taken as the research instance. In this paper, a modified formula for the Terzaghi ultimate bearing capacity of a foundation is established based on rock mass strength criteria. As per the engineering practice, the maximum roof pressure of the inclined shaft is calculated to be 2.7 MPa, and the minimum pressure value from the modified formula is only 0.3 MPa. In order to control the floor heave of the roadway, a U-type steel inverted arch and bolts support scheme was designed. After calculating through the mechanical model of the inverted arch, its bearing capacity is 0.56 Mpa. Through comparison and analysis of various supporting schemes, finally, the “U-type steel + inverted arch + pouring concrete + backwall grouting” technology is selected, and the engineering practice shows that the supporting scheme can effectively improve surrounding rock stability.

scholarly journals Research of the Surrounding Rock Deformation Control Technology in Roadway under Multiple Excavations and Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Ming Su ◽  
Xiaohui Gao
Keyword(s):  
Coal Mine ◽  
Reference Value ◽  
Field Investigation ◽  
Surrounding Rock ◽  
Rock Deformation ◽  
Control Effect ◽  
Deformation Control ◽  
Bolt Stress ◽  
Advanced Support ◽  
Surrounding Rock Deformation

To effectively control the large surrounding rock deformation of the mining roadway under multiple excavations and mining in Wangcun coal mine, the field investigation, numerical simulation, field test, and monitoring were conducted, and the characteristics of stress and deformation evolution of the surrounding rock under the influence of multiple excavations and mining were analyzed; then the collaborative supporting technology of high prestressed bolt and short anchor cables was proposed in this study. The results show the following: (1) under the influence of multiple excavations and mining, the peak vertical stress of the typical air-return roadway reaches 23 MPa, and the deformation increases by about 2.8 times after the mining of adjacent panel. (2) The principle of the roadway support under the influence of multiple excavations and mining in Wangcun coal mine is determined; from the perspective of prestress, we can conclude that the active support of short anchor cables is better than that of long anchor cables. (3) Based on the results of the field monitoring, the bolt stress can be divided into four stages: the loss stage of prestress, the sudden-decrease stage of the roof periodic weighting, the decrease stage of advanced support, and the rapid-increase stage of strong disturbance. Due to the large anchorage range of anchor cables, there is no decrease stage of advanced support. After the application of prestress, the bolt stress of side bolts and top bolts decreases, and the reduction amplitude is up to 30 kN. (4) As the panel advances, the deformation of the surrounding roadway increases, and the growth rate is also increasing gradually. However, the final displacement of the roof, floor, and two sides is within 18 mm. The bolt and anchor cables are not broken, and the control effect is good. The research results have a certain reference value for similar roadway control.

scholarly journals Comprehensive technical support for safe mining in ultra-close coal seams: A case study

2021 ◽  
pp. 014459872110093
Author(s):  
Wei Zhang ◽  
Jiawei Guo ◽  
Kaidi Xie ◽  
Jinming Wang ◽  
Liang Chen ◽  
...  
Keyword(s):  
Coal Seam ◽  
Technical Support ◽  
Surrounding Rock ◽  
Coal Seams ◽  
Deformation Control ◽  
Hard Roof ◽  
Working Face ◽  
Close Coal Seams ◽  
Safe Mining

In order to mine the coal seam under super-thick hard roof, improve the utilization rate of resources and prolong the remaining service life of the mine, a case study of the Gaozhuang Coal Mine in the Zaozhuang Mining Area has been performed in this paper. Based on the specific mining geological conditions of ultra-close coal seams (#3up and #3low coal seams), their joint systematic analysis has been performed, with the focus made in the following three aspects: (i) prevention of rock burst under super-thick hard roof, (ii) deformation control of surrounding rock of roadways in the lower coal seam, and (iii) fire prevention in the goaf of working face. Given the strong bursting tendency observed in upper coal seam and lower coal seam, the technology of preventing rock burst under super-thick hard roof was proposed, which involved setting of narrow section coal pillars to protect roadways and interleaving layout of working faces. The specific supporting scheme of surrounding rock of roadways in the #3low1101 working face was determined, and the grouting reinforcement method of local fractured zones through Marithan was further proposed, to ensure the deformation control of surrounding rock of roadways in lower coal seams. The proposed fire prevention technology envisaged goaf grouting and spraying to plug leaks, which reduced the hazard of spontaneous combustion of residual coals in mined ultra-close coal seams. The technical and economic improvements with a direct economic benefit of 5.55 million yuan were achieved by the application of the proposed comprehensive technical support. The research results obtained provide a theoretical guidance and technical support of safe mining strategies of close coal seams in other mining areas.

scholarly journals Study on instability failure mode and monitoring early warning standard of surrounding rock in fully weathered argillaceous sandstone section of large section tunnel

2019 ◽  
Vol 136 ◽  
pp. 04023
Author(s):  
Ming Zhao ◽  
Ke Li ◽  
Hong Yan Guo ◽  
KaiCheng Hua
Keyword(s):  
Limit State ◽  
Stable State ◽  
Simulation Software ◽  
Surrounding Rock ◽  
Large Section ◽  
Rock Stability ◽  
Geological Conditions ◽  
Construction Step ◽  
The Face ◽  
The Stability

Based on the special geological conditions of a tunnel in Qingyuan section of Huizhou-Zhanzhou Expressway, FLAC3d numerical simulation software is used to simulate the rheological properties and instability of surrounding rock in large-section fully weathered sandstone section, and the stability and loss of surrounding rock are analyzed. The deformation of the dome and the face at steady state is analyzed. It is found that: 1) when the surrounding rock is in a stable state, the deformation curve of the dome is smooth. When the surrounding rock of the face is unstable, the front of the face appears ahead. Deformation should be first strengthened on the surrounding rock in front of the face. 2) The arched foot is an important part of the instability of the surrounding rock. In order to prevent the expansion of the collapsed part, the arched part should be reinforced. 3) In order to obtain the limit state of surrounding rock stability, the strength of surrounding rock is reduced, and the strength reduction coefficient corresponding to the displacement sudden point is taken as the safety factor of rock stability around the hole, and the stability safety coefficients of surrounding rock of each construction step are greater than 1.2. 4) The dynamic standard values of deformation control in the whole construction stage are obtained by analyzing the deformation curves of each data monitoring point with time in the corresponding time period of each construction step.

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