Study on mechanical properties of surrounding rock and shaft safety pillar in exploitation of extremely thin reef

The left-hand rolling-thread steel bolt has been proposed as a new bolt for controlling roadway surrounding rock. To explore the mechanism of a left-hand rolling-thread steel bolt in roadway surrounding rock control, its pretightening forces, tensile strengths, anchoring forces, and maximum working resistances were compared to normal right-hand full-thread steel bolts in the engineering context of the 1301 haulage roadway in the Daxing Coal Mine. Then, the left-hand threaded steel bolt was applied to the 1301 haulage roadway that the right-hand threaded steel bolt failed to control. The results indicated that due to the different effective tensile section area, the yield strength and tensile strength of the left-hand threaded steel bolt with the same material and diameter were more than 10% larger than those of the right-hand threaded steel bolt. Due to the different thread directions, the anchoring forces of the Φ18 and Φ20 left-hand threaded steel bolts were 46.2% and 33.3% greater than those of the right-hand threaded steel bolts, respectively. In the 1301 haulage roadway, the maximum pull-out force of the left-hand rolling-thread steel bolt with the same diameter was obviously greater than that of the right-hand full thread steel bolt. The displacements of the 1301 haulage roadway supported by the left-hand threaded steel bolt were not great. So, the left-hand threaded steel bolt can effectively control the surrounding rock in the 1301 haulage roadway.

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Experimental Study on Mechanical Properties of Jurassic Soft Rock in Shajihai Mining Area of Xinjiang

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.353-356.20 ◽

2013 ◽

Vol 353-356 ◽

pp. 20-23

Author(s):

Xiao Lei Wang ◽

Shun Xi Yan ◽

Guang Can Zhang

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Compression Test ◽

Mechanical Test ◽

Triaxial Compression ◽

Soft Rock ◽

Mining Area ◽

Surrounding Rock ◽

Test Results ◽

Support Design

According to the problemsof serious deformation of soft rock roadways and lack of system andcomprehensive study on surrounding rock characteristics and failure mechanismin Shajihai mining area, this paper carried out a series of mechanicalexperiments on the characteristics of surrounding rock in this area includinguniaxial compression test, triaxial compression test and water absorption propertiestest. Mechanical test results show that the compressive strength of surroundingrock of roadway is generally low, and mudstone compressive strength is thelargest which is 19.23 MPa, and compressive strength of the minimum is coalwhich is 11.32 MPa under natural condition. However sandstone and mudstone’sability of water absorbing is strong, and coal saturation strength issignificantly greater than that of mudstone and sandstone. Therefore, we shouldmake full use of the strength of coal in roadway layout and support design.

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The Study on Mechanical Properties of Karst Tunnel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.243-249.3399 ◽

2011 ◽

Vol 243-249 ◽

pp. 3399-3402

Author(s):

Bin Li ◽

Tai Yue Qi

Keyword(s):

Mechanical Properties ◽

Numerical Models ◽

Side Wall ◽

Surrounding Rock ◽

Karst Tunnel ◽

Safety Coefficient ◽

Coefficient Distribution ◽

Unfavorable Effect ◽

Adverse Influence ◽

The Stability

Several numerical models were built by FLAC3D to simulate tunnel with karst around spandrel, tunnel with karst around springe, tunnel with karst around inverted arch and tunnel with karst around side wall. The influence of karsts on the deformation of lining and the safety coefficient distribution of surrounding rock after excavation was analyzed. The results from the numerical modeling suggest as follows: karst around spandrel has extremely unfavorable effect on the deformation of lining and the safety of surrounding rock above the vault, karst around side wall also seriously affect the stability of tunnel due to the asymmetry pressure on tunnel caused by karst, consequently, auxiliary measures should be taken to handle these two cases; karst around springe and karst around inverted arch has limited adverse influence on the overall safety of tunnel, backfill measures are enough to handle these two cases.

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Rock Long-Term Strength Parameters Determination of a Salt Cavern Gas Storage

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.353-356.1685 ◽

2013 ◽

Vol 353-356 ◽

pp. 1685-1688

Author(s):

Li Na Ran ◽

Hua Bin Zhang ◽

Zhi Yin Wang

Keyword(s):

Mechanical Properties ◽

Rock Salt ◽

Gas Storage ◽

Surrounding Rock ◽

Creep Process ◽

Term Strength ◽

Salt Cavern ◽

Study Results ◽

Salt Cavern Gas Storage

In order to determine the long-term mechanical properties of surrounding rock of salt cavern gas storage, long tri-axial creep test studies on rock salt of the field were carried out. Based on the test data, long-term strength of rock salt was determined, and comparatively analysis was conducted combined with of the instantaneous test. The study results show that: Considering the axial strain, radial strain and volumetric strain to determine the long-term strength of rock salt can ensure reliability of the results. Under the same condition, the less salt content, the value of long-term strength is higher. Tri-axial creep process has a different effect degree between cohesion and internal friction angle; it is more sensitive to cohesion. The strain limit should be considered for the stability analysis of multi-bedded salt cavern gas storage construction and pay more attention about the mechanical properties of the interlayer parts. The study results provide references for researching the surrounding rock long-term mechanical properties of salt cavern gas storage.

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Force and Deformation Characteristics during the Reconstruction and Expansion of Shallow Single-Tube Tunnels into Large-Span Multiarch Tunnels

Advances in Materials Science and Engineering ◽

10.1155/2019/2783784 ◽

2019 ◽

Vol 2019 ◽

pp. 1-13

Author(s):

Yanling Jia ◽

Yongxu Xia ◽

Xindong Chen ◽

Yongdi Zhou ◽

Xingbo Han ◽

...

Keyword(s):

Mechanical Properties ◽

Numerical Simulation ◽

Great Influence ◽

Surrounding Rock ◽

Surface Subsidence ◽

Stress And Strain ◽

Partition Wall ◽

Single Tube ◽

Left And Right ◽

The Right

At present, there are an ever-increasing number of tunnel expansion projects in China. Studying the mechanical properties of the expanded tunnels is of great significance for guiding their safe construction. Through model testing and numerical simulation, the mechanical properties of a double-arch tunnel constructed through the expansion of the middle pilot heading from an existing single-tube tunnel were studied. The variation characteristics of the surface subsidence, surrounding rock stress, and stress and strain of the middle partition wall and lining during the tunnel reconstruction and expansion were investigated. The mechanism for transferring stress and strain between the left and right tunnel tubes was studied by a numerical simulation method. The results showed that the surface subsidence caused by the excavation of the left (i.e., the subsequent) tunnel tube was larger, and the maximum surface subsidence occurred at the right (i.e., the first) tunnel tube. The surrounding rock on the middle wall was the sensitive part of the tunnel excavation, the stress of the surrounding rock at the left spandrel of the right tunnel tube fluctuated and exhibited the most complex variation, and the stress of the surrounding rock at the right spandrel of the left tunnel tube exhibited the largest variation. The excavation of the left tunnel tube had a great influence on the forces of the middle partition wall and the lining structure of the right tunnel tube, the middle partition wall was subjected to eccentric compression towards the left tunnel tube, and the stress at the left spandrel under the initial support of the right tunnel tube exhibited complex variations. The excavation of the left and right tunnel tubes had a great influence on the stability of the surrounding rock, as well as on the force-induced deformation of the middle partition wall and the support structure, within the width of the single tunnel tube span behind the tunnel working face. Due to the different construction sequences, the stress and strain at the symmetric measurement points of the middle partition wall, as well as the left and right tunnel support structures, were very different.

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Experimental Study of Primary Lining Tunnel Concrete after Thirty Years of Operation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.732.403 ◽

2015 ◽

Vol 732 ◽

pp. 403-406 ◽

Cited By ~ 4

Author(s):

Filip Vogel ◽

Radoslav Sovják ◽

Ondřej Holčapek ◽

Libor Mařík ◽

Jiří Šach

Keyword(s):

Mechanical Properties ◽

Experimental Study ◽

Ground Water ◽

Surrounding Rock ◽

Sprayed Concrete ◽

Aggressive Environment

This article shows the acquisition and testing of concrete from tunnel primary lining. The main objective of this article was to describe the mechanical properties of primary lining tunnel concrete at higher age. The primary lining was made from dry mixture sprayed concrete. The primary lining concrete was in contact with the surrounding rock continuously. The surrounding rock could be dry or with ground water. Some surrounding rocks could produce a highly aggressive environment for concrete. The question was, whether the sprayed concrete is still in service after 30 years in this environment.

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Optimization of Tunnel Support Type through Fault Zone

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.580-583.1184 ◽

2014 ◽

Vol 580-583 ◽

pp. 1184-1187

Author(s):

Ke Li ◽

Han Guo

Keyword(s):

Mechanical Properties ◽

Finite Element Method ◽

Reinforced Concrete ◽

Fault Zone ◽

Critical Issue ◽

Surrounding Rock ◽

The Other ◽

Support Pressure ◽

Tunnel Support ◽

Tunnel Safety

The mechanical properties of tunnel surrounding rock in fault zone is usually quite weak, and the support pressure and displacement are larger than other sections, so the support type in fault zone is a critical issue for tunnel safety. Three types of tunnel support through fault zone were analyzed by finite element method (FEM): ①Reinforced concrete support, ②bolting-shotcreting and reinforced concrete support,③grouting and reinforced concrete support. The result shows that support stress and surrounding rock displacement with grouting and reinforced concrete support is quite smaller than the other support types.

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Study on the Deformation Characters of the Coal Roadways with Compound Rock Strata and Water Spraying Roof

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.214.287 ◽

2012 ◽

Vol 214 ◽

pp. 287-291 ◽

Cited By ~ 1

Author(s):

Hong Yan ◽

Teng Fei Xu ◽

Jun Wang

Keyword(s):

Mechanical Properties ◽

Surrounding Rock ◽

Rock Deformation ◽

Abscission Layer ◽

Measuring Device ◽

Coal Roadway ◽

Roof Caving ◽

Rock Strata ◽

Surrounding Rock Deformation ◽

Roof Deformation

The coal roadways with water spraying usually have large surrounding rock deformation or roof abscission layer, especially to the roadways with compound rock strata roof, which could lead to sudden roof caving accidents, so it is imperative to research the roof characters and the corresponding controlling methods. In this paper, we firstly analyze the main reasons and characters of the roof deformation or its stability failure with bolt and cable supporting, and then the mechanical properties of the roof are tested in the lab, which could afford detailed datum to the further analysis. Based on the comprehensive researching results of this complex roof, a set of measuring device for the value of water spraying in single roof hole is developed and then applied to a typical coal roadway. Finally, some effective controlling methods are put forward to prevent from the large deformation of the roadways.

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Development of Modified Grouting Material and Its Application in Roadway Repair Engineering

Geofluids ◽

10.1155/2021/8873542 ◽

2021 ◽

Vol 2021 ◽

pp. 1-15

Author(s):

Yang Yu ◽

Zhengyuan Qin ◽

Xiangyu Wang ◽

Lianying Zhang ◽

Dingchao Chen ◽

...

Keyword(s):

Mechanical Properties ◽

Surrounding Rock ◽

Engineering Practice ◽

Mass Ratio ◽

Control Effect ◽

Grouting Pressure ◽

Grouting Material ◽

Wide Range ◽

Grouting Reinforcement ◽

Grouting Materials

It is very extraordinary for the success of coal mine roadway grouting with the following factors of high early strength, good fluidity, and convenient pumping, but the existing grouting materials make it difficult to achieve the above characteristics at the same time. Therefore, a modified grouting material is developed, which is composed of two kinds of dry materials A and B, which are mixed with water and in equal amounts. The physical and mechanical properties of modified grouting materials under different ratios were tested by laboratory orthogonal test, and the optimal ratio of grouting materials and additives was obtained: (1) the water-cement ratio is 0.8 : 1; (2) base material: the mass ratio of cement, fly ash, bentonite, and water is 1 : 0.3 : 0.1 : 1.44; (3) admixture: the mass ratio of water reducer C, accelerator D, and retarder E is 1.5% : 0.05% : 0.3%. The basic properties of the modified grouting materials were studied from the aspects of slurry flow state, diffusion range, and grouting parameters by using the numerical simulation method, and the reinforcement mechanism of slurry to the broken surrounding rock properties of the roadway was revealed: (1) the grouting pressure is the main factor affecting the slurry diffusion radius; (2) the mechanical properties of the roadway surrounding rock are improved, the plastic zone and deformation of surrounding rock are reduced, and the active support function of the anchor and cable is enhanced through grouting reinforcement; (3) the control effect of the roadway is improved, and the balanced bearing with anchorage structure of the roadway surrounding rock is realized through grouting reinforcement. On this basis, the modified grouting material is applied to roadway repair and reinforcement engineering practice. The field monitoring data show that the production practices were guided by roadway repair and reinforcement technology with the modified grouting material, as the core of the roadway surrounding rock control effect is good, and the modified grouting material has a wide range of application prospects.

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Deformation Mechanism and Support Technology of Deep and High-Stress Soft Rock Roadway

Advances in Civil Engineering ◽

10.1155/2021/6634299 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Lujing Zheng ◽

Yujun Zuo ◽

Yafei Hu ◽

Wei Wu

Keyword(s):

Mechanical Properties ◽

Bearing Capacity ◽

High Stress ◽

Soft Rock ◽

Physical And Mechanical Properties ◽

Surrounding Rock ◽

Rock Fragmentation ◽

The Stability ◽

Soft Rock Roadway ◽

Rock Roadway

In this study, the analysis and control of stability of surrounding rock in deep fractured soft rock roadway located in the underground mine of Jinfeng gold mine in Guizhou Province, China, has been investigated. The surrounding rock of roadway has been analyzed to characterize its deformation and failure mechanism through field survey, testing of rock physical and mechanical properties, in situ stress measure, analysis of mineral components of rock, and investigation of rock fragmentation degree. Based on the numerical simulation technology, the influence of different factors on the stability of roadway is studied. The physical and mechanical properties of surrounding rock and the bearing capacity of surrounding rock layer are to be improved to maintain the stability of broken soft rock roadway as high ground stress, rock fragmentation, and poor lithology leading to tunnel instability. Hence, a high-strength “cable bolt + fiber-reinforced shotcrete + steel mesh + split sets + resin bolt + cement grouting” combined support system has been proposed to improve the effective bearing structure significantly with high integrity and bearing capacity.

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