scholarly journals Study on Fracture Distribution and Local Brittleness Characteristics Based on Stepwise Regression Method

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Wanchun Zhao ◽  
Xiaohan Feng ◽  
Tingting Wang
Keyword(s):  
Rock Mass ◽  
Brittle Fracture ◽  
Rock Fracture ◽  
Ct Scanner ◽  
Mineral Contents ◽  
Evolution Mechanism ◽  
Intrinsic Nature ◽  
Region Division ◽  
Macroscopic Fracture ◽  
Fracture Distribution

The brittleness of rock is an important parameter that influences and controls the evolution mechanism of the fracture and formation of a fracture net. The existing methods of brittle characterization are describing the brittleness of rock mass as a whole. They lack reliability descriptions to guide the fracture strike and improve the volume of the reservoir. It is considered that the macroscopic brittle fracture of a rock is the process of continuous initiation and propagation of local fractures in the rock mass under the action of external loads. The macroscopic fracture is the appearance caused by a local rupture to a certain extent, and the local rupture is the root cause of macroscopic fracture. The study of the local brittleness of a rock can reveal the intrinsic nature of its fracture behavior and can reflect the evolution mechanism of fracture more directly and accurately. In this paper, coring sampling in field outcrop is first carried out, and the break evolution law of core is described by a CT scanner. The mineral compositions in the core are determined by a mineral analysis diffractometer. The regulation of the rock local brittleness with different mineral contents is analyzed. And a new method for local brittle region division and characterization of rock has been developed. This method gives the connotation relation of the rock brittle fracture as a whole induced by a local brittle fracture. And it provides a new approach to study the law of a rock fracture.

Influence exerted by underground excavation shape and by effective stresses on the formation of a tensile strain zone at a depth greater than 1 km

2020 ◽  
pp. 67-75
Author(s):  
Van Min Nguyen ◽  
V. A. Eremenko ◽  
M. A. Sukhorukova ◽  
S. S. Shermatova
Keyword(s):  
Rock Mass ◽  
Cross Sections ◽  
Tensile Strain ◽  
Rock Fracture ◽  
Strain Analysis ◽  
Surrounding Rock ◽  
Underground Excavation ◽  
Secondary Stress ◽  
Principal Stresses ◽  
Mining Depth

The article presents the studies into the secondary stress field formed in surrounding rock mass around underground excavations of different cross-sections and the variants of principal stresses at a mining depth greater than 1 km. The stress-strain analysis of surrounding rock mass around development headings was performed in Map3D environment. The obtained results of the quantitative analysis are currently used in adjustment of the model over the whole period of heading and support of operating mine openings. The estimates of the assumed parameters of excavations, as well as the calculations of micro-strains in surrounding rock mass by three scenarios are given. During heading in the test area in granite, dense fracturing and formation of tensile strain zone proceeds from the boundary of e ≥ 350me and is used to determine rough distances from the roof ( H roof) and sidewalls ( H side) of an underground excavation to the 3 boundary e = 350me (probable rock fracture zone). The modeling has determined the structure of secondary stress and strain fields in the conditions of heading operations at great depths.

scholarly journals Fracture System and Rock-Mass Characterization by Borehole Camera Surveying: Application in Dimension Stone Investigations in Geologically Complex Structures

2021 ◽  
Vol 11 (2) ◽  
pp. 764
Author(s):  
Ivica Pavičić ◽  
Ivo Galić ◽  
Mišo Kucelj ◽  
Ivan Dragičević
Keyword(s):  
Rock Mass ◽  
Fractured Rock ◽  
Low Cost ◽  
Fracture Pattern ◽  
Dimension Stone ◽  
Rock Mass Characterization ◽  
Size And Shape ◽  
Distribution Parameters ◽  
Borehole Camera ◽  
Fracture Distribution

The successful exploration of dimension stone mainly depends on the quality, size, and shape of extractable blocks of dimension stone. The investigated area is in the Pelješac Peninsula (Croatia), in the External Dinarides orogeny, built from thick carbonate succession, characterized by relatively small deposits of high-quality dimension stone. These conditions demand challenging geological investigations in the “pre-quarry” phase to find optimal quarry location. The size and shape of dimension stone blocks are mainly controlled by fracture pattern systems. In the rugged, covered terrains, it is very hard to obtain a satisfactory amount of fracture data from the surface, so it is necessary to collect them from the underground. Borehole camera technology can visualize the inner part of the rock mass and measure the fracture characteristics. The main conclusions are as follows: (1) the digital borehole camera technology provides a quick, effective, and low-cost geological survey of fractured rock mass; (2) statistical fracture distribution parameters, P10, fracture spacing, Volumetric Joint Count (Jv) based on borehole wall survey can reflect the integrity of rock mass, providing a solid decision-making base for further investment plans and dimension stone excavation method.

scholarly journals Estimating the rockburst hazard of hard rocks based on laboratory test results

2019 ◽  
Vol 129 ◽  
pp. 01008
Author(s):  
Iuliia Fedotoval ◽  
Nikolay Kuznetcov ◽  
Eduard Kasparyan
Keyword(s):  
Rock Mass ◽  
Rock Fracture ◽  
Standard Test ◽  
Standard Equipment ◽  
Rock Classification ◽  
Rockburst Hazard ◽  
Hazard Degree ◽  
Laboratory Test Results ◽  
Dynamic Fractures ◽  
Deformation Patterns

The results of laboratory tests of samples are used to estimate rock proneness to dynamic fractures, in particular, by brittleness index. A common drawback of the approaches in use is that they do not expressly consider the main condition of dynamic rock fracture – rock mass ability to accumulate energy when loaded. The article discusses the results of studies of the nature of elastic energy accumulation during loading and deformation of samples of various rocks under uniaxial compression in order to assess the degree of their explosion. The approach is original as it studies the deformation curve of rocks at the pre-peak stage that may be obtained with any standard equipment without the use of special-purpose test (“rigid”) devices. Results of the studies conducted on standard test devices have allowed us to identify two different deformation patterns for the rock type tested with further establishment of criteria of rock classification by the degree of proneness to dynamic fractures. This approach is of practical value as it specifies the geomechanics zoning method of the rock mass and improves the assessment of rockburst hazard degree of specific areas at deposits being developed.

Research on the Cavern Stability and Rock Fracture with Different Joint Groups

2012 ◽  
Vol 188 ◽  
pp. 96-100 ◽  
Author(s):  
Hai Ping Ma ◽  
Wei Shen Zhu ◽  
Song Yu ◽  
Jing Wang
Keyword(s):  
Rock Mass ◽  
Loading Condition ◽  
Fracture Process ◽  
Process Analysis ◽  
Rock Fracture ◽  
Rock Stability ◽  
Joint Rock Mass ◽  
Deformation Stress ◽  
Cavern Stability ◽  
Joint Rock

The numerical simulation using DDARF was carried out to analysis the rock samples with two and four cracks under uniaxial loading condition. Contrastive research was made about the fracture process analysis of rock mass with joints sets at the three different angles. The rock stability with difference of joint rock mass was compared when the lateral coefficient of initial stress varied. It is shown that distribution of joint groups will bring effects on rock surroundings in controlling deformation, stress status and stability.

Study of Seepage Properties of Fractured Rock Mass Based on Improved K-Means Clustering Algorithm

2013 ◽  
Vol 405-408 ◽  
pp. 310-315
Author(s):  
Hai Qing Guo ◽  
Bo Wen ◽  
Xiao Feng Bai
Keyword(s):  
Rock Mass ◽  
Clustering Algorithm ◽  
Fractured Rock ◽  
Rock Fracture ◽  
Fractured Rock Mass ◽  
Dam Foundation ◽  
Fracture Geometry ◽  
Basic Task ◽  
Matlab Program ◽  
Seepage Properties

Seepage properties of fractured rock mass are of prime importance for hydraulic engineering and accurate description of rock fracture geometry parameters is an important and basic task in rock hydraulics. In this paper, an improved K-means clustering algorithm for structural plane of fractured rock mass was first brought forward and the corresponding Matlab program for discontinuity orientations partitioning was compiled and then used in the fitting analysis of dominant orientations of certain dam foundation rock mass. On this basis, combining calculation formulas of multi-group fractures, the permeability tensor and principle value was calculated for the actual dam foundation. The results provide a theoretical and computational reference for other similar projects.

scholarly journals Failure Mechanisms of Brittle Rocks under Uniaxial Compression

2017 ◽  
Vol 47 (3) ◽  
pp. 59-80 ◽  
Author(s):  
Taoying Liu ◽  
Ping Cao
Keyword(s):  
Rock Mass ◽  
Crack Initiation ◽  
Failure Mechanism ◽  
Shear Crack ◽  
Fractured Rock ◽  
Rock Fracture ◽  
Wing Crack ◽  
Rock Bridge ◽  
Brittle Rocks ◽  
Shear Connection

AbstractThe behaviour of a rock mass is determined not only by the properties of the rock matrix, but mostly by the presence and properties of discontinuities or fractures within the mass. The compression test on rock-like specimens with two prefabricated transfixion fissures, made by pulling out the embedded metal inserts in the pre-cured period was carried out on the servo control uniaxial loading tester. The influence of the geometry of pre-existing cracks on the cracking processes was analysed with reference to the experimental observation of crack initiation and propagation from pre-existing flaws. Based on the rock fracture mechanics and the stress-strain curves, the evolution failure mechanism of the fissure body was also analyzed on the basis of exploring the law of the compression-shear crack initiation, wing crack growth and rock bridge connection. Meanwhile, damage fracture mechanical models of a compression-shear rock mass are established when the rock bridge axial transfixion failure, tension-shear combined failure, or wing crack shear connection failure occurs on the specimen under axial compression. This research was of significance in studying the failure mechanism of fractured rock mass.

scholarly journals Considerations in Fracture of Rock Mass by Using Trial Hydraulic Rock Fracture Machine.

1997 ◽  
pp. 249-258
Author(s):  
Yoshinori Inada ◽  
Koichi Nohara ◽  
Takeshi Uehara ◽  
Takashi Matsumoto ◽  
Masaaki Okamoto ◽  
...  
Keyword(s):  
Rock Mass ◽  
Rock Fracture

scholarly journals Experimental Study on the Flow Behavior of Grout Used in Horizontal Directional Drilling Borehole Grouting to Seal Mining-Induced Overburden Fractures

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Jinfeng Ju ◽  
Jialin Xu ◽  
Jing Yang
Keyword(s):  
Rock Mass ◽  
Fractured Rock ◽  
Flow Behavior ◽  
Groundwater Resources ◽  
Rock Fracture ◽  
Mining Area ◽  
Tensile Failure ◽  
Directional Drilling ◽  
Horizontal Directional Drilling ◽  
Fracture Types

The development of water-conducting fractures from underground coal mining is a geological cause of groundwater loss. Sealing mining-induced rock fracture channels through borehole grouting is an effective way to protect groundwater resources. A ground-based engineering test was conducted at the Gaojiabao coal mine that utilized horizontal directional drilling (HDD) to grout and seal water-conducting overburden fractures. This study carried out a theoretical and experimental exploration using HDD to evaluate the development characteristics and grout hydraulic conductivity of these mining-induced fractures. The results showed that, as a result of varying fracture morphologies in different zones of the mining overburden, multiple fracture types were sequentially exposed as the HDD borehole advanced from the original rock mass outside the mining area towards the mining-induced fractured rock mass. The fracture types were exposed in the following order: compressive shear fractures, tensile failure fractures, and bed separation fractures. Moreover, the void characteristics of the exposed fractures in the borehole were significantly different at different drilling horizons, which affected the flow behavior and sealing performance of the injected grout. Lastly, three typical orders in which the different types of fractures were sequentially exposed by the borehole were summarized, and further analysis of the orders led to a scheme for determining drilling horizons favorable for efficient fracture sealing. The results of this study will enable efficient grout sealing of the fractures caused by mining and reduce groundwater loss.

Heat Flux to Fluids Within a Rock Fracture in a Geothermal System

2010 ◽  
Author(s):  
Dustin Crandall ◽  
Goodarz Ahmadi ◽  
Grant Bromhal
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Rate ◽  
Numerical Study ◽  
Rock Fracture ◽  
Working Fluid ◽  
Geothermal System ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Ct Scanner

Fractures in rocks enable the motion of fluids through the large, hot geologic formations of geothermal reservoirs. The heat transfer from the surrounding rock mass to the fluid flowing through a fracture depends on the geometry of the fracture, the fluid/solid properties, and the flow rate through the fracture. A numerical study was conducted to evaluate the changes in heat transfer to the fluid flowing through a rock fracture with changes in the flow rate. The aperture distribution of the rock fracture, originally created within Berea sandstone and imaged using a CT-scanner, is well described by a Gaussian distribution and has a mean aperture of approximately 0.6 mm. Water was used as the working fluid, enabling an evaluation of the efficiency of heat flux to the fluid along the flow path of a hot dry geothermal system. As the flow through the fracture was increased to a Reynolds number greater than 2300 the effect of channeling through large aperture regions within the fracture were observed to become increasingly important. For the fastest flows modeled the heat flux to the working fluids was reduced due to a shorter residence time of the fluid in the fracture. Understanding what conditions can maximize the amount of energy obtained from fractures within a hot dry geologic field can improve the operation and long-term viability of enhanced geothermal systems.

scholarly journals Study on Strain Characterization and Failure Location of Rock Fracture Process Using Distributed Optical Fiber under Uniaxial Compression

Sensors ◽  
2020 ◽  
Vol 20 (14) ◽  
pp. 3853
Author(s):  
Shiang Xu ◽  
Shuangming Wang ◽  
Pingsong Zhang ◽  
Duoxing Yang ◽  
Binyang Sun
Keyword(s):  
Rock Mass ◽  
Optical Fiber ◽  
Uniaxial Compression ◽  
Circumferential Strain ◽  
Rock Fracture ◽  
Test System ◽  
Dynamic Strain ◽  
Strain Response ◽  
Strain Characterization ◽  
Distributed Optical Fiber

A rock fracture test is a very important method in the study of rock mechanics. Based on the Mechanics Test System (MTS), the dynamic strain response of the failure process of cylindrical granite specimens under uniaxial compression was observed by using distributed optical fiber strain sensors. Two groups of tests were designed and studied for rock sample fracturing. The main comparison and analysis were made between the distributed optical fiber testing technology and the MTS testing system in terms of the circumferential strain response curve and the evolution characteristics of strain with time. The strain characterization of distributed optical fiber in the process of rock fracturing was obtained. The results show that the ring strains measured by the distributed optical fiber sensor and the circumferential strain gauge were consistent, with a minimum ring strain error of 1.27%. The relationship between the strain jump or gradient band of the distributed optical fiber and the crack space on the sample surface is clear, which can reasonably determine the time of crack initiation and propagation, point out the location of the rock failure area, and provide precursory information about rock fracture. The distributed optical fiber strain sensor can realize the linear and continuous measurement of rock mass deformation, which can provide some reference for the study of macro damage evolution and the fracture instability prediction of field engineering rock mass.

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