Failure mechanism of surrounding rock with high stress and confined concrete support system

Abstract Surrounding rock control is a big challenge in roadway with high stress in deep underground engineering. To address this issue, Zhaolou coal mine – a typical kilometer deep well is taken as engineering background to monitor and analyze the original support scheme. The analysis shows that the following main reasons lead to the support failure in roadway with high stress in deep underground coal mine. Roadway deformation is large and lasts longer with a large extent of damage; all anchor bolts are in severely damaged surrounding rock zone without reliable adhesive basis; and U-shaped steel arch unevenly contacts with surrounding rock without sufficient bearing capacity. With summary of support failure mechanisms on-site, a concept of “high-strength and integrity support” is put forward; a support system with square steel confined concrete (SQCC) is developed; and a full scale in-door comparative test is conducted on its core component – SQCC arch and also on the conventional U29 arch. The research shows the bent and damaged legs of U29 arch result in dramatic reduction of bearing capacity of arch. However, the SQCC arch with similar steel content has a bearing capacity of 2.15 times of that of U29 arch and still has a higher post bearing capacity even after the arch is deformed dramatically. Quantitative evaluation index is established such as vault displacement control rate and bolt strength utilization rate; comparative analysis is made on surrounding rock control mechanism and the mechanical properties of support components under the influence from the four factors – arch strength, geostress, lateral pressure coefficient and surrounding rock mechanical parameters; and good control effect on surrounding rock of SQCC support is verified. Comparative tests are conducted on site. The monitoring results show the roadway surrounding rock deformation on the test section of SQCC support is only 21.2% of that on test section of U29 arch support; and no yield and damage occurs on the test section of SQCC support. Therefore, the SQCC support system is proved to be effective on surrounding rock control.

[1]  Quansheng Liu,et al.  Application of a combined support system to the weak floor reinforcement in deep underground coal mine , 2014 .

[2]  Anders Ansell,et al.  Laboratory testing of a new type of energy absorbing rock bolt , 2005 .

[3]  Ernesto Villaescusa,et al.  Quantifying the performance of resin anchored rock bolts in the Australian underground hard rock mining industry , 2008 .

[4]  Shucai Li,et al.  Model test study on surrounding rock deformation and failure mechanisms of deep roadways with thick top coal , 2015 .

[5]  Mark S. Diederichs,et al.  Mechanical analysis of circular liners with particular reference to composite supports. For example, liners consisting of shotcrete and steel sets , 2009 .

[6]  Hongyuan Liu,et al.  Experimental study on failure behaviour of deep tunnels under high in-situ stresses , 2015 .

[7]  Manchao He,et al.  Development of a novel energy-absorbing bolt with extraordinarily large elongation and constant resistance , 2014 .

[8]  J. Lin,et al.  Investigation on support pattern of a coal mine roadway within soft rocks — a case study , 2015 .

[9]  Raghuvir Singh,et al.  Studies on failure behaviour of wire rope used in underground coal mines , 2016 .

[10]  Qi Wang,et al.  Failure mechanism of bolting support and high-strength bolt-grouting technology for deep and soft surrounding rock with high stress , 2016 .

[11]  Rajendra Singh,et al.  Field and numerical modelling studies for an efficient placement of roof bolts as breaker line support , 2017 .

[12]  Charlie C. Li,et al.  A new energy-absorbing bolt for rock support in high stress rock masses , 2010 .

[13]  Liang Song,et al.  Improvement of the U-shaped steel sets for supporting the roadways in loose thick coal seam , 2013 .

[14]  Qi Wang,et al.  Mechanical behaviors analysis on a square-steel-confined-concrete arch centering and its engineering application in a mining project , 2017 .

[15]  Q Wang.  Mechanical properties and failure mechanism of square type confined concrete arch centering , 2015 .

[16]  Baotang Shen,et al.  Coal Mine Roadway Stability in Soft Rock: A Case Study , 2014, Rock Mechanics and Rock Engineering.

[17]  Louis Ngai Yuen Wong,et al.  Systematic monitoring of the performance of anchor systems in fractured rock masses , 2010 .

[19]  Zhang Nong.  Fracture Characteristics of a Soft Rock Roadway: Staged and Zoned Control , 2009 .

[20]  Pinnaduwa Kulatilake,et al.  Discontinuum–Equivalent Continuum Analysis of the Stability of Tunnels in a Deep Coal Mine Using the Distinct Element Method , 2016, Rock Mechanics and Rock Engineering.

[21]  Xie Sheng-ron.  Anchor-spray-injection strengthened bearing arch supporting mechanism of deep soft rock roadway and its application , 2014 .