Geological discontinuity persistence: Implications and quantification

Shear behaviors of ‘real’ natural un-matching joints of granite with equivalent joint roughness coefficients

ABSTRACT In order to study the effect of temperature on the pore structure of lignite, liquid nitrogen adsorption and scanning electron microscopy (SEM) were used to analyze the change of pore structure of Indonesian lignite after heating, and the relationship between fractal dimension and pore structure of lignite after heating was analyzed. The effect of drying temperature on the pore structure of lignite was investigated by effective moisture diffusion coefficient and X-ray diffraction (×RD). The results show that between 40 and 160 ℃, with the increase of drying temperature, the N2 adsorption and desorption of Indonesian lignite shows a trend of first increasing and then decreasing. The fractal dimensions D 1 and D 2 of some lignites have a linear relationship with the specific surface area and average pore diameter, respectively, and the fractal dimension D 3 has a linear relationship with the average pore diameter. As the drying temperature increases, the moisture transfer resistance decreases and the effective moisture diffusivity of lignite ( ) increases accordingly. There is a linear positive correlation between and the average pore diameter. The increase of the lignite aromatic system and the decrease of the crystallite stacking height have certain effects on the pore structure of lignite.

Study on pore structure characteristics of Indonesian lignite during low temperature drying process

Fracture Development Patterns and Micro–Macrostructural Fractal Characteristics of Acid–Base Coal Samples

Stability of rock masses at shallow depth is often controlled by shear behavior of discontinuities. This is an important issue in an engineering environment as well as from societal point of view. With regard to shear behavior assessment through laboratory investigation, direct shear test under constant normal load were carried out on two types of rock such that joint in granite and sandstone bedding planes. From each rock types three samples of similar joint roughness coefficient (varied between 0.86-1.52) were selected for investigation. It should be noted that same sample was tested thrice at three different consecutively increasing low normal stresses (ranges: 0.22-0.23 MPa, 0.45-0.46 MPa and 0.69-0.70 MPa respectively). At low normal stresses (0.22-0.23 MPa), three types of shear behavioral characteristics of natural rock discontinuity (i.e. for both types of rock) were observed whereas at relatively higher normal stresses (0.45-0.70 MPa), shear behaviors along these discontinuities plane were found to be broadly similar. In general, the differences of peak shear strengths and peak shear displacement increases as applied normal stress increases with subsequent stages of shearing. The probable reason behind individuality of results was explained. Keywords—shear behavior of discontinuity; surface morphology; joint roughness coefficient; peak shear strength; joint in granite; sandstone bedding plane.

/pdf/shear-behavior-of-planar-unfilled-rock-discontinuities-with-dmmlm1ep4g.pdf

Shear behavior of planar unfilled rock discontinuities with reference to surface morphology under constant normal load

In order to quantify the characteristics of the surface of jointed rock mass, new equipment, the three-dimensional laser surface topography instrument, was used to accurately measure surface morphology of joints. Scan pictures and parameters were obtained to describe the rock joint surface characteristics, for example, the height frequency of surface, and mean square roughness. Using the method of fractal dimension, the values of joint roughness coefficient (JRC) were calculated based on the above parameters. It could access to the joint surface rock sample morphology of the main parameters of characteristic. The maximum peak height is 2.692 mm in the test joint plane. The maximum profile height is 4.408 mm. JRC value is 6.38 by fractal dimension computing. It belongs to the smooth joint surface. The results show that it is a kind of the effective method to quantitatively evaluate the surface topography by the three-dimensional laser surface topography instrument and the fractal dimension method. According to the results, during the process of underground large-scale mining, safe measures to prevent slip failure of the joint plane by controlling surface tension and shear mechanical response were proposed.

Morphology characteristics of joint surface in rock mass

The strength parameters of fissured ore-rock mass are mainly influenced by the mechanical parameters of rock block and the characteristic parameters of the joints.In order to estimate the strength parameters of fissured ore-rock mass in underground mining,the quantitative Geological Strength Index(GSI) rock mass classification system is used,and the effect of mining activities is considered.The GSI system is quantified by using joint spacing and Joint Roughness Coefficient(JRC).The fissured ore-rock mass from Zu-Cu deposit in Tongkeng mining area is taken as the research object,the joint spacing and Joint Roughness Coefficient are obtained from the geological survey of rock mass,and the strength parameters of the hanging wall and the footwall rock are estimated.The results show that the GSI method can determine the parameters of fissured ore-rock mass.The strength parameters of the hanging wall and footwall rocks are obtained as follows: the modulus of elasticity,5.749 GPa and 4.483 GPa,respectively;the cohesions,3.126 MPa and 2.772 MPa,respectively;the angle of internal friction,24.56° and 23.08°,respectively.These mechanical parameters can be regarded as basic parameters for mining design.

Determination of mechanical parameters of fractured rock mass based on GSI

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Morphology characteristics of joint surface in rock mass

Determination of mechanical parameters of fractured rock mass based on GSI