scholarly journals Field Monitoring of the Deformation and Internal Forces of the Surrounding Rock and Support Structures in the Construction of a Super-Span High-Speed Railway Tunnel—A Case Study

2020 ◽  
Vol 10 (15) ◽  
pp. 5182
Author(s):  
Daoping Liu ◽  
Dingli Zhang ◽  
Qian Fang ◽  
Zhenyu Sun ◽  
Jiwei Luo ◽  
...  
Keyword(s):  
Contact Pressure ◽  
High Speed ◽  
Field Monitoring ◽  
Surrounding Rock ◽  
Internal Stresses ◽  
Support Structures ◽  
Axial Forces ◽  
Geological Conditions ◽  
Internal Forces

A super-span tunnel that has the characteristics of a large excavation area, a small high-span ratio and a significant spatial effect exhibits a complex mechanical response during the excavation process. In this paper, taking the Badaling Great Wall station in Beijing, China as the engineering background, a case study of field monitoring a super-span tunnel has been presented. A typical monitoring section was selected in the super-span transition section of the tunnel and the deformation and forces of both the surrounding rock and the support structures were systematically monitored. The dynamic evolution and the spatial distribution characteristics of the monitoring data, including the internal displacement of the surrounding rock, the tunnel displacement, the contact pressure between the surrounding rock and the primary supports, the contact pressure between the primary and secondary supports, the axial forces in the bolts and cables, the internal forces in both the steel arches and the secondary supports and the internal stresses of the surrounding rock, were analyzed. The results of the monitoring and the analyses have shown that the deformation and the forces acting on both the surrounding rock and the tunnel’s lining are directly related to the construction procedures, the geological conditions and the locations in the super-span tunnel. According to the results, a few suggestions to improve the construction of the tunnel have been proposed.

scholarly journals Effect of Improvement and Application of Composite Prefabricated Vertical Drain Method in Marine Soft Ground: A Case Study

2019 ◽  
Vol 2019 ◽  
pp. 1-18 ◽  
Author(s):  
Jianqing Jiang ◽  
Reqiang Liu
Keyword(s):  
High Speed ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Improvement ◽  
Field Monitoring ◽  
Hyperbolic Model ◽  
Soft Ground ◽  
Prefabricated Vertical Drains ◽  
Prefabricated Vertical Drain

One of the commonly used techniques to improve marine soft ground is the drainage consolidation method by plastic board drains (PBDs). But some complex marine soft ground will cause construction inconvenience of PBDs in certain areas of these sites, thus affecting the improvement effect. An alternative possible approach to overcoming these deficiencies may be the combination of PBDs and sand wick drains (SWDs) (i.e., composite prefabricated vertical drains (CPVDs)) as vertical drainage channels in the same site. In order to verify the suitability and performance of this method in marine soft ground improvement, a case study was performed based on the field monitoring and construction of the marine soft ground of an intercity express railway project in China. The construction procedure using the CPVD system, the field monitoring instrumentation scheme, and the design of fill surcharge level were described, and the field monitoring data were presented. The settlement characteristics, dissipation features of pore water pressure, and the horizontal movement pattern were assessed. In addition, predictions of ultimate settlement, postconstruction settlement, and consolidation degree were discussed by applying a modified hyperbolic model. The results show that the marine ground improved by the CPVD system is suitable for the construction of intercity express railway and high-speed railway. The improvement construction period of complex marine soft ground will be greatly shortened by the proposed parallel construction programme. This work will provide technical supports and application reference for the improvement of the similar marine soft ground.

Anisotropic Relaxation of Internal Forces in a Wound Reel of Magnetic Tape

1967 ◽  
Vol 34 (4) ◽  
pp. 888-894 ◽  
Author(s):  
H. Tramposch
Keyword(s):  
Surface Roughness ◽  
Thermal Expansion ◽  
Stress Distribution ◽  
Magnetic Tape ◽  
Digital Computer ◽  
High Speed ◽  
Coefficient Of Thermal Expansion ◽  
Internal Stresses ◽  
Numerical Examples ◽  
Internal Forces

Equations were developed to describe the relaxation of the internal stresses of a wound reel of magnetic tape, with allowances for the effects of surface roughness between tape layers and unequal thermal expansion of hub and tape-layer body. Numerical examples obtained with the aid of a high-speed digital computer indicated that the surface roughness as well as the unequal thermal expansion of hub and tape-layer body greatly affect the internal stress distribution. Essentially independent of the surface roughness, a typical reel, when stored at 120 F after being wound at 70 F and when the coefficient of thermal expansion of the hub is three times the value of the tape material, will approach stress-free conditions about 80 percent earlier than when it is stored at the winding temperature.

scholarly journals A Case Study of Optimization and Application of Soft-Rock Roadway Support in Xiaokang Coal Mine, China

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Shuai Guo ◽  
Xun-Guo Zhu ◽  
Xun Liu ◽  
Hong-Fei Duan
Keyword(s):  
Soft Rock ◽  
Surrounding Rock ◽  
Geological Conditions ◽  
Floor Heave ◽  
Roadway Support ◽  
Soft Rock Roadway ◽  
Surrounding Rock Stress ◽  
Rock Roadway

The roadway of S2S2 fully mechanized caving face (FMCF) in Xiaokang Coal Mine is one of the most typical deep-buried soft-rock roadways in China and had been repaired several times. In order to figure out the failure reasons of the original roadway support, the geological conditions were investigated, the surrounding rock stress was monitored, the rib displacement, roof separation, and floor heave were in situ measured, and the performance of the U-shaped steel support was simulated. The above analysis results indicated that the support failure was mainly caused by (1) the unreasonable arch roadway section, (2) the high and complex surrounding rock stress, (3) the failure control of the floor heave, and (4) the inadequate self-supporting capacity of the surrounding rock. For optimizing, the roadway section was changed to circle and a new full-section combined support system of “belt-cable-mesh-shotcrete and U-shaped steel-filling behind the support” was adopted, which could specifically control the floor heave, allow the roadway deformation in control, and improve the self-supporting ability and stress field of the surrounding rock. To determine the support parameters, the selected U-shaped steel support was verified by simulation, and various bolt-cable support schemes were simulated and compared. Finally, such an optimized support scheme was applied in the roadway of the next replacement FMCF. The in situ monitoring showed that the rib-to-rib convergence and roof-to-floor convergence were both controlled within 600 mm, which indicated that the roadway was effectively controlled. This case study has important reference value and guiding function for the optimal design of the soft-rock roadway support with similar geological conditions.

scholarly journals Mechanism and Procedure of Repeated Borehole Drilling Using Wall Protection and a Soft Structure to Prevent Rockburst: A Case Study

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Yongliang He ◽  
Mingshi Gao ◽  
Xu Dong ◽  
Xin Yu
Keyword(s):  
Energy Absorption ◽  
Control Method ◽  
Stability Control ◽  
Surrounding Rock ◽  
Support Structure ◽  
Geological Conditions ◽  
Borehole Drilling ◽  
The Stability ◽  
Mine Roadways

With the increasing mining depth of coal mines, the occurrence of rockburst, especially in mine roadways, is becoming critical as a severe dynamic disaster. This paper explores the stability control of deep mine roadways and solves the contradiction between the support and pressure relief of roadways by studying the use of an internal steel pipe for wall protection and a soft structure for energy absorption during repeated borehole drilling. Numerical simulations are performed to examine the effects of active support technology on the support structure during repeated drilling. Internal steel pipes can effectively prevent the support structure from being damaged. When the soft structure cracks, the energy transmitted from the rockburst to the roadway is significantly reduced. According to the deformation and failure characteristics of the surrounding rock of the 21170 roadway, the combination of anchor active support, hydraulic lifting shed support, and soft structure energy absorption is proposed. An engineering case study shows that the support method can effectively maintain the stability of the surrounding rock and ensure the safe mining of the working face. The proposed control method can provide reference for the prevention and control of rockburst in mine roadways under similar geological conditions.

scholarly journals Temporal and Spatial Effect of Surrounding Rock and Supporting Construction of a Large Soil Tunnel

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Wanjun Ye ◽  
Yuntao Wu ◽  
Ming Chen ◽  
Chong Gao
Keyword(s):  
Contact Pressure ◽  
Rock Pressure ◽  
Release Rate ◽  
Rapid Growth ◽  
High Speed ◽  
Surrounding Rock ◽  
Measuring Point ◽  
Finite Element Software ◽  
Surrounding Rock Pressure ◽  
Secondary Lining

Based on the Zaosheng No. 3 tunnel of the Yinchuan-Xi’an high-speed railway, the surrounding rock pressure, contact pressure of the primary support, and secondary lining and internal force of the secondary lining concrete are systematically tested using a vibrating wire sensor, and the correlation between the advance construction distance and the surrounding rock release rate is studied with finite element software. The results show that the pressure on the surrounding rock is low when the deeply buried soil tunnel is excavated and can be divided into three stages: rapid growth, slow growth, and flattening with time. It is more reasonable to calculate the surrounding rock pressure by using tunnel planning calculations. For the contact pressure, although the value of each measuring point in the inverted arch changes a little, the arch pressure obviously has the characteristics of rapid growth and a sharp rebound. Most of the test points of the second lining concrete show a compression state, which is far less than the ultimate compressive strength. At the same time, the initial support of the tunnel bears a large load, while the secondary lining bears a relatively small force, and the load sharing ratio of the two ranges between 0.1 and 0.7; with the progress of the excavation section, the surrounding rock deformation (deformation release rate) increases gradually. When the excavation face is close to the monitoring section, the deformation (deformation release rate) is the most severe. With the increase in the distance between the excavation section and the monitoring section, the deformation (deformation release rate) tends to be flat.

Relaxation of Internal Forces in a Wound Reel of Magnetic Tape

1965 ◽  
Vol 32 (4) ◽  
pp. 865-873 ◽  
Author(s):  
H. Tramposch
Keyword(s):  
Magnetic Tape ◽  
Digital Computer ◽  
Isotropic Material ◽  
High Speed ◽  
Mechanical Damage ◽  
Elastic Behavior ◽  
Internal Stresses ◽  
Sufficient Time ◽  
Numerical Examples ◽  
Internal Forces

Equations were developed to predict the relaxation of the internal stresses of a wound reel of magnetic tape, assuming a homogeneous and isotropic material which, under shear, exhibits instantaneous elasticity, delayed elasticity, and creep; and under hydrostatic stressing, shows elastic behavior. Numerical examples obtained with the aid of a high-speed digital computer indicated that the internal stresses introduced during the winding operation continue to relax. Given sufficient time in storage, the wound reel will approach stress-free conditions, thus exposing the tape to mechanical damage during transportation and reuse.

scholarly journals Cooperative Control Mechanism of Long Flexible Bolts and Blasting Pressure Relief in Hard Roof Roadways of Extra-Thick Coal Seams: A Case Study

2021 ◽  
Vol 11 (9) ◽  
pp. 4125
Author(s):  
Zhe Xiang ◽  
Nong Zhang ◽  
Zhengzheng Xie ◽  
Feng Guo ◽  
Chenghao Zhang
Keyword(s):  
Coal Seam ◽  
Cooperative Control ◽  
Field Tests ◽  
Surrounding Rock ◽  
Deep Hole ◽  
Coal Seams ◽  
Thick Coal Seam ◽  
Structure Damage ◽  
Hard Roof

The higher strength of a hard roof leads to higher coal pressure during coal mining, especially under extra-thick coal seam conditions. This study addresses the hard roof control problem for extra-thick coal seams using the air return roadway 4106 (AR 4106) of the Wenjiapo Coal Mine as a case study. A new surrounding rock control strategy is proposed, which mainly includes 44 m deep-hole pre-splitting blasting for stress releasing and flexible 4-m-long bolt for roof supporting. Based on the new support scheme, field tests were performed. The results show that roadway support failure in traditional scenarios is caused by insufficient bolt length and extensive rotary subsidence of the long cantilever beam of the hard roof. In the new proposed scheme, flexible 4-m-long bolts are shown to effectively restrain the initial expansion deformation of the top coal. The deflection of the rock beam anchored by the roof foundation are improved. Deep-hole pre-splitting blasting effectively reduces the cantilever distance of the “block B” of the voussoir beam structure. The stress environment of the roadway surrounding rock is optimized and anchorage structure damage is inhibited. The results provide insights regarding the safe control of roadway roofs under extra-thick coal seam conditions.

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.

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