|
|
|
| CHARACTERISTICS AND FORMATION MECHANISM OF CORE DISCING IN DEEP ROCK MASS |
| LI Zhanhai1，LI Shaojun2，FENG Xiating1，2，ZHOU Hui2，CHEN Bingrui2，ZHANG Chuanqing2 |
(1. School of Resources and Civil Engineering，Northeastern University，Shenyang，Liaoning 110004，China；
2. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China) |
|
|
|
|
Abstract According to borehole cores with the length more than 1 500 m in deep tunnels at Jinping II hydropower station，the information of the macro-damaged characteristics，quantity and thickness distribution of discing core were collected and the spatial distribution of core discing was analyzed. Then，the influences of different buried depths，geologic structure，tunnel geometric size，drilling diameter and directions on core discing were studied in combination with the results of elastic wave test and digital borehole images. Simultaneously，by applying scanning electron microscope technique for discs? surface，the micro-damage mechanism was discussed. The results indicated that：(1) The relationship between the quantity and thickness distribution was similar to a power function form. The quantity of core discing increased with depth and tunnel dimension. Within the zone of 3 times of tunnel diameter，core discing occurred more frequently. (2) The convex-concave formation was related to stress distribution，internal damage and mineral structure types. (3) Core discing often occurred under the joint action of geological and external effects. The native micro defects，structural plane and external disturbance were the discing foundation；the local stress concentration and stress release were the power of discing；the continuous drilling was the intrinsic cause of core broken into pies；the radial cut-compressive，axial tensile stress and lateral expansion of rock cores were the mechanical response of rock mass fracture. (4) Discing zone characteristics were the comprehensive reflection of rock damage weakening，rock mass structure and local stress concentration.
|
|
Received: 15 April 2011
|
|
|
|
| [1] OBERT L，STEPHENSON D E. Stress conditions under which core discing occurs[J]. Society of Mining Engineers，1965，(9)：227–235.
[2] KAGA N，MATSUKI K，SAKAGUCHI K. The in-situ stress states associated with core discing estimated by analysis of principal tensile stress[J]. International Journal of Rock Mechanics and Mining Sciences，2003，40(5)：653–665.
[3] MATSUKI K，KAGA N，YOKOYAMA T，et al. Determination of three dimensional in situ stress from core discing based on analysis of principal tensile stress[J]. International Journal of Rock Mechanics and Mining Sciences，2004，41(7)：1 167–1 190.
[4] 尚岳全，孙 琪. 天荒坪电站岩芯饼化机制分析[J]. 地质灾害与环境保护，1991，2(2)：49–52.(SHANG Yuequan，SUN Qi. Analysis core mechanism of Tianhuangping powerstation[J]. Geological Hazards and Environment Preservation，1991，2(2)：49–52.(in Chinese))
[5] 李树森，聂德新，任光明. 岩芯饼裂机制及其对工程地质特性影响的分析[J]. 地球科学进展，2004，19(增 1)：376–379.(LI Shusen，NIE Dexin，REN Guangming. The fracture mechanism of discal drill core and its influence on characteristic of engineering geology[J]. Advance in Earth Sciences，2004，19(Supp.1)：376–379.(in Chinese))
[6] 阮小平，李方全. 茅坪800 m钻孔饼状岩芯分析[J]. 地震学报，1994，16(2)：190–194.(YUAN Xiaoping，LI fangquan. Analysis of core discing of Maoping 800 m drilling hole[J]. Acta Seismologica Sinica，1994，16(2)：190–194.(in Chinese))
[7] 刘竹华，姚宝魁，杨家录. 钻孔岩芯饼状断裂破坏机制[J]. 工程地质学报，1997，5(4)：330–334.(LIU Zhuhua，YAO Baokui，YANG Jialu. Fracture mechanism of the discal drill core[J]. Journal of Engineering Geology，1997，5(4)：330–334.(In Chinese))
[8] LIM S S，MARTIN C D. Core discing and its relationship with stress magnitude for Lac du Bonnet granite[J]. International Journal of Rock Mechanics and Mining Sciences，2010，47(2)：254–264.
[9] 姜谙男，曾正文，唐春安. 岩芯成饼单元安全度三维数值试验及地应力反馈分析[J]. 岩石力学与工程学报，2010，29(8)：1 610–1 617. (JIANG Annan，ZENG Zhengwen，TANG Chun′an. Three-dimensional numerical test of element safety degree of rock core discing and feed-back analysis of geostresses[J]. Chinese Journal of Rock Mechanics and Engineering，2010，29(8)：1 610–1 617.(in Chinese))
[10] BUNGER A P. Stochastic Analysis of core discing for estimation of in situ stress[J]. Rock Mechanics and Rock Engineering，2010，43(3)：275–286.
[11] CORTHESY R，LEITE M H. A strain-softening numerical model of core discing and damage[J]. International Journal of Rock Mechanics and Mining Sciences，2008，45(3)：329–350.
[12] KANG S S，ISHIGURO Y，OBARA Y. Evaluation of core disking rock stress and tensile strength via the compact conical-ended borehole overcoring technique[J]. International Journal of Rock Mechanics and Mining Sciences，2006，43(8)：1 226–1 240.
[13] 吴世勇，王 坚，王 鸽. 锦屏水电站辅助洞工程地下水及治理对策[J]. 岩石力学与工程学报，2007，26(10)：1 959–1 967.(WU Shiyong，WANG Jian，WANG Ge. Underground water and its treatment strategy in auxiliary tunnels of Jinping hydropower project[J]. Chinese Journal of Rock Mechanics and Engineering，2007，26(10)：1 959–1 967.(in Chinese))
[14] LI S J，FENG X T，LI Z H，et al. In-situ experiments on width and evolution characteristics of excavation damaged zone in deeply buried tunnels[J]. Science China Technology Sciences，2011，54(Supp.1)：167–174. |
|
|
|
2011, Vol. 30 
