A borehole stability study by newly designed laboratory tests on thick-walled hollow cylinders

作     者：S.S.Hashemi N.Melkoumian A.Taheri 

作者机构：Deep Exploration Technologies Cooperative Research Centre School of Civil Environmental and Mining Engineering University of Adelaide 

出 版 物：《Journal of Rock Mechanics and Geotechnical Engineering》 (岩石力学与岩土工程学报（英文版）)

年 卷 期：2015年第7卷第5期

页      面：519-531页

核心收录：

学科分类：0820[工学-石油与天然气工程] 082001[工学-油气井工程] 081901[工学-采矿工程] 0819[工学-矿业工程] 08[工学] 0818[工学-地质资源与地质工程] 0815[工学-水利工程] 0813[工学-建筑学] 0814[工学-土木工程] 

基　　金：supported by the Deep Exploration Technologies Cooperative Research Centre whose activities are funded by the Australian Government’s Research Programme 

主　　题：Real-time monitoring Experimental investigation Thick-walled hollow cylinder(TWHC) Poorly cemented sand formations 

摘      要：At several mineral exploration drilling sites in Australia, weakly consolidated formations mainly consistof sand particles that are poorly bonded by cementing agents such as clay, iron oxide cement or *** formations are being encountered when drilling boreholes to the depth of up to 2 0 0 m. To studythe behaviour of these materials, thick-walled hollow cylinder （TWHC） and solid cylindrical syntheticspecimens were designed and prepared by adding Portland cement and water to sand grains. The effectsof different parameters such as water and cement contents, grain size distribution and mixture curingtime on the characteristics of the samples were studied to identify the mixture closely resembling theformation at the drilling site. The Hoek triaxia! cell was modified to allow the visual monitoring of graindebonding and borehole breakout processes during the laboratory tests. The results showed the significanceof real-time visual monitoring in determining the initiation of the borehole breakout. The sizescaleeffect study on TWHC specimens revealed that with the increasing borehole size, the ductility ofthe specimen decreases, however, the axial and lateral stiffnesses of the TWHC specimen remain *** different confining pressures the lateral strain at the initiation point of boreholebreakout is considerably lower in a larger size borehole （2 0 mm） compared to that in a smaller one（10 mm）. Also, it was observed that the level of peak strength increment in TWHC specimens decreaseswith the increasing confining pressure.