地震研究

具有多种断层结构岩样的形变和破裂特征的试验研究^*

(1.云南大学地球物理系,昆明 650091; 2.云南省地震局,昆明 650224; 3.昆明理工大学激光研究所,昆明 650041)

关键词：多个切缝岩样; 多种断层结构; 激光全息计量; 定点应变; 微破裂信息分析

Experimental Study of the Characteristics of Deformation and Fracture of Rock Block with Various Structure of the Fault

HU Yi-li¹,XU Jun²,XU Zhao-yong²,CHEN Shun-yun²

(1.Department of Earth Sciences,Yunnan University,Kunming 650091,Yunnan,China)(2.Earthquake Administration of Yunnan Province,Kunming 650224,Yunnan,China)(3.Laser Institute,Kunming University of Science and Technology,Kunming 650041,Yunnan,China)

Keywords：prefabricated cracks; various structure of fault; laser holometry; rock block; strain; micro-crack analysis

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参考文献

在岩石板上切割出多条切缝并以石膏填充,将其分为3个构造特征区:A区(断层交汇区)、B区(左行左列岩桥区)、C区(右行左列岩桥区)。采用双轴加压、定点应变、声发射信息系统和实时全息干涉计量方法(激光)进行观测研究。结果表明:在岩样破坏孕育过程中,各个特征区都出现了特大破裂。每个特大破裂发生前定点应变、激光干涉条纹图(应变场)和声发射信息都出现了特征变化。特大破裂的发生有先后,其前兆特征的出现也有先后,并且各区有各自的特点,某些前兆还可能在各区之间交替出现。研究认为,三个区的断层结构性质不同,这就导致了不同的破裂顺序,甚至产生不同的前兆现象。

V-shaped block boundaries consisting of en echelon faults(slots or prefabricated cracks)were cut in a coarse-grained granite board.The slots were filled with gypsum.According to the structural characteristics,the board was divided into three zones:Zone A(where the faults converge),Zone B(where the faults form left-lateral and left-stepping rock bridges),and Zone C(where the faults form right-lateral and left-stepping rock bridges).An observational study was made by means of biaxial loading,fixed-point strain measurement,AE information system,and real-time holometry(laser).Results are as the following:All extra-fractures emerge in various structural zones during process of preparing failure of the sample.Before extra-fracturing,the variation characteristics such as the strains at measuring points increased with the increase of stress,message of AE events and fringes are observed by real-time holometry.Extra-fractures occurred in order,and the precursors of the extra-fractures emerged in order too.The three zones had their own characteristics with regard to the fracturing.Some precursors emerge alternately in various zones.When examined from the structural characteristics,it can be seen that the three zones are places where different structures meet and therefore are sensitive sections for events to occur.This has led to different orders of fracture or even resulted in different precursors.

引言
1 试验方法
2 分析方法
3 大理花岗岩的实验结果
4 讨论与结论

图1 实验装置简图试样构造、加力方式及仪器布置框图(a)和实时全息干涉计量摄像装置(b)<br/>Fig.1 Scheme of the experimental setup block diagram of the sample structure,way of loading and apparatus arrangement(a)and set-up of photography by real-time holometry(b)

图1 实验装置简图试样构造、加力方式及仪器布置框图(a)和实时全息干涉计量摄像装置(b)
Fig.1 Scheme of the experimental setup block diagram of the sample structure,way of loading and apparatus arrangement(a)and set-up of photography by real-time holometry(b)

图2 加力方式及各测点应变随压力增加的变化(a)加载过程示意图;(b)第一次保压(32 MPa)制作干板之前各测点应变随压力增加的变化; (c)第一次保压制作干板之后(32～39 MPa)各测点应变随压力增加的变化;(d)试样破坏前(应力45 MPa之后)的应变变化(A区:1、2、3; B区:4、5、6; C区:7、8、9)。
Fig.2 Loading pattern and the variation of strain at different measuring points with the increase of load(a)Schematics of loading process;(b)Variation of strain at different measuring points with the increase of load before the load was kept constant(stress is 31.7 MPa)while making holographic plate for the first time;(c)Variation of strain at different measuring points with the increase of load(from 32MPa to 39MPa)after the load had been kept constant while making holographic plate for the first time;(d)Strain variation on the sample before the failure of rock

图3 第一次保压制作干板之后(应力从32MPa到39MPa)实时全息观测(a)时间靠前;(b)时间靠后<br/>Fig.3 The first round of real-time holographic observation after the load had been kept constant while making holographic plate for the first time—the stress is from 32MPa to 39MPa,in which(a)is of an earlier and(b)is of a later time

图3 第一次保压制作干板之后(应力从32MPa到39MPa)实时全息观测(a)时间靠前;(b)时间靠后
Fig.3 The first round of real-time holographic observation after the load had been kept constant while making holographic plate for the first time—the stress is from 32MPa to 39MPa,in which(a)is of an earlier and(b)is of a later time

图4 第二次保压制作干板之后的实时全息观测(a)时间靠前;(b)时间居中;(c)时间居中;(d)时间靠后<br/>Fig.4 The second round of real-time holographic observation after the load had been kept constant while making holographic plate for the second time—the stress is from 39MPa to 45MPa,in which(a)is of the earliest time,(b)and(c)are in the intermediate while(d)is of the latest time

图4 第二次保压制作干板之后的实时全息观测(a)时间靠前;(b)时间居中;(c)时间居中;(d)时间靠后
Fig.4 The second round of real-time holographic observation after the load had been kept constant while making holographic plate for the second time—the stress is from 39MPa to 45MPa,in which(a)is of the earliest time,(b)and(c)are in the intermediate while(d)is of the latest time

图5 第三次保压制作干板之后(邻近主破裂前)的实时全息观测(a)时间靠前;(b)居中;(c)时间靠后<br/>Fig.5 The third round of real-time holographic observation after the load had been kept constant while making holographic plate for the third time—the stress is great than 45MPa just before the failure of rock,in which (a)is of the earlier time,(b)is of the later,while(c)shows the position of macrocracks

图5 第三次保压制作干板之后(邻近主破裂前)的实时全息观测(a)时间靠前;(b)居中;(c)时间靠后
Fig.5 The third round of real-time holographic observation after the load had been kept constant while making holographic plate for the third time—the stress is great than 45MPa just before the failure of rock,in which (a)is of the earlier time,(b)is of the later,while(c)shows the position of macrocracks

图6 声发射事件定位结果图(圆圈表示AE事件,圈越大事件越大; 星号表示PZT探头; 圈边数字表示AE事件的序号)(a)应力在32～39 MPa之间;(b)应力在39～45 MPa之间;(c)、(d)和(e)应力均大于45 MPa;(f)应力从32 MPa到破裂<br/>Fig.6 Variation of microcracks(AE events)location with time(circle:AE event,the larger the circle,the larger the event; *:PZT transducer; numeral by a circle represents the serial number of event occurrence)(a)32 MPa<stress<39 MPa;(b)39 MPa<stress<45 MPa;(c),(d),and(e)stress>45 MPa;(f)stress from 32 MPa to failure

图6 声发射事件定位结果图(圆圈表示AE事件,圈越大事件越大; 星号表示PZT探头; 圈边数字表示AE事件的序号)(a)应力在32～39 MPa之间;(b)应力在39～45 MPa之间;(c)、(d)和(e)应力均大于45 MPa;(f)应力从32 MPa到破裂
Fig.6 Variation of microcracks(AE events)location with time(circle:AE event,the larger the circle,the larger the event; *:PZT transducer; numeral by a circle represents the serial number of event occurrence)(a)32 MPa<stress<39 MPa;(b)39 MPa<stress<45 MPa;(c),(d),and(e)stress>45 MPa;(f)stress from 32 MPa to failure

图7 试件不同区域声发射频度与强度的关系(n:频率; N:累积频率)(a)整个试样;(b)A区;(c)B区;(d)C区<br/>Fig.7 Relation between the AE frequency and AE intensity in different zones of the sample(n:frequency; N:accumulating frequency)(a)The whole sample;(b)Zone A of the sample;(c)Zone B of the sample;(d)Zone C of the sample

图7 试件不同区域声发射频度与强度的关系(n:频率; N:累积频率)(a)整个试样;(b)A区;(c)B区;(d)C区
Fig.7 Relation between the AE frequency and AE intensity in different zones of the sample(n:frequency; N:accumulating frequency)(a)The whole sample;(b)Zone A of the sample;(c)Zone B of the sample;(d)Zone C of the sample