Experimental Study on the Dilatancy and Fracturing Behavior of Soft Rock Under Unloading Conditions

doi:10.1007/s40999-016-0144-9

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	Experimental Study on the Dilatancy and Fracturing Behavior of Soft Rock Under Unloading Conditions
	Pan, Yucong 1; Huang, Xing 1; Liu, Quansheng 1,2; Liu, Bin 1; Liu, Xuewei 1; Liu, Jianping 1
刊名	INTERNATIONAL JOURNAL OF CIVIL ENGINEERING
	2017
卷号	15 期号:6A 页码:921-948
关键词	Unloading Damage-dilatancy Fracture-bulking Time-dependent damage and fracturing Creep-dilatancy Deformation mechanism
ISSN号	1735-0522
DOI	10.1007/s40999-016-0144-9
英文摘要	To reveal the deformation mechanism during tunneling in deep soft ground, triaxial unloading confining pressure tests and triaxial unloading creep tests were carried out on sandy mudstone specimens to study the dilatancy and fracturing behavior of soft rock. In the triaxial unloading confining pressure tests, the stress path and different unloading rates were considered to reflect the unloading characteristics of the excavation methods. The unloading rate effects and the rock damage evolution law are studied. The following conclusions are obtained from the results. Firstly, when the unloading rate is smooth, the peak strengths and deviatoric stress-strain curves under the unloading condition are close to those under the conventional loading condition. Secondly, the post-peak brittle characteristics are more apparent with the increasing unloading rates. Thirdly, the soft rock undergoes five deformation and failure regimes of elasticity, pre-peak unloading damage-dilatancy, post-peak brittle drop, linear strain softening and residual perfect plasticity under quasi-static smooth unloading of mechanized excavation which is mainly focused on in this study. Fourthly, the damage evolution law at the pre-peak damage-dilatancy stage follows an exponential function. Fifthly, during the post-peak stages, multistage microfractures are initiated, propagated and finally coalesced forming a shear-fragmentation band with a certain thickness, accompanied by significant volumetric dilatancy. In the triaxial unloading creep tests, multistep unloading of the confining pressure was applied, while the axial pressure was kept constant. The results show that when the deviatoric stress is larger and the experienced creep time is longer, the unloading effect and creep characteristics become more apparent accompanied with obvious lateral dilatancy, eventually leading to significant creep-dilatancy. The progressive failure with time is caused by the damage accumulating with time-dependent crack expansion, which can be called as 'time-dependent damage and fracturing'. The reasons for the above evolution process are presented, then the deformation mechanism of soft rock is revealed. The soft rock deformation mainly consists of two parts. One part is the pre-peak damage-dilatancy and post-peak fracture-bulking produced at the excavation unloading instant. The other part is creep-dilatancy caused by time-dependent damage and fracturing in a period of time after excavation. The above-mentioned results of damage, dilatancy and fractures evolution process are in good agreement with the in situ monitoring results and previous studies about the surrounding rock convergence, fracturing and EDZ (excavation damaged zone) development.
WOS研究方向	Engineering
语种	英语
出版者	SPRINGER
WOS记录号	WOS:000408742500007
内容类型	期刊论文
源URL	[http://119.78.100.198/handle/2S6PX9GI/4130]
专题	岩土力学所知识全产出_期刊论文国家重点实验室知识产出_期刊论文
作者单位	1.Chinese Acad Sci, Inst Rock & Soil Mech, State Key Lab Geomech & Geotech Engn ; 2.Wuhan Univ, Sch Civil Engn, Key Lab Geotech & Struct Engn Safety Hubei Prov
推荐引用方式 GB/T 7714	Pan, Yucong,Huang, Xing,Liu, Quansheng,et al. Experimental Study on the Dilatancy and Fracturing Behavior of Soft Rock Under Unloading Conditions[J]. INTERNATIONAL JOURNAL OF CIVIL ENGINEERING,2017,15(6A):921-948.
APA	Pan, Yucong,Huang, Xing,Liu, Quansheng,Liu, Bin,Liu, Xuewei,&Liu, Jianping.(2017).Experimental Study on the Dilatancy and Fracturing Behavior of Soft Rock Under Unloading Conditions.INTERNATIONAL JOURNAL OF CIVIL ENGINEERING,15(6A),921-948.
MLA	Pan, Yucong,et al."Experimental Study on the Dilatancy and Fracturing Behavior of Soft Rock Under Unloading Conditions".INTERNATIONAL JOURNAL OF CIVIL ENGINEERING 15.6A(2017):921-948.