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<< Click to Display Table of Contents >> Navigation: GMS - GeoMechanical Survey > Joints |
On the right side of the work area you can find the tables for data input.
The field measurements are performed along a sampling line, materialized on the rocky front with metric strip fixed at the ends of the survey, and so are detected all the discontinuities encountered proceeding from one end to another.
Data regarding joint is entered in this panel; each time at least one pair of values dip and dip direction is inserted and the belonging to a family of joint is chosen, on the diagram is plotted the joint of the joint, using the diagrams that the user chooses form the "Computation" or "View" menu.
Position of the joint in space. The surfaces of joint may be represented as a plane whose joint is identified by a pair of angles (dip, dip direction) or (dip, strike) where dip is the inclination, strike is the direction and dip direction is the azimuth of the joint (in the Anglo-Saxon terminology respectively dip, strike and dip direction refers to a plan).
Dip direction - the azimuth of the immersion measured in degrees, counted clockwise from the North and expressed with a three-digit number from 000 ° to 360 °.
Dip - the maximum inclination of the middle plane of the joint, expressed in degrees with two-digit numbers from 00 ° to 90 °.
Distance between adjacent joints measured in the direction orthogonal to the joints them self. Normally it refers to the average or modal spacing of a cracks system. Together with the orientation and the persistence determines the shape and size of the blocks in which is divided the rock mass. Since the measure d, expressed in cm, is performed orthogonally to the joint, must be adjusted taking into account of the angle δ between the joint and the sample line: S = d sin δ.
Length of the joint observed in outcrop. Can give a rough measure of the areal extent or penetration depth of a joint. Unit of measurement: meter.
Distance between the facing edges of a joint in which the intervening space is filled with air or water.
The thin apertures can be measured with a gauge, while the large ones with a ruler graduated in mm. They are detected along the intersection with the alignment of the survey.
Roughness of facing surfaces of a joint and undulation relatively to the median plane of the joint. Both the roughness and its morphological evolution contribute to shear resistance, especially in the case of interconnected structures and without relative displacements.
The classification is divided into 9 classes of roughness, and a coefficient Jr ("Joint Roughness Number") corresponds to each class.
Compressive strength equivalent of the facing edges of a joint. It may be less than the strength of the rock mass due to exposure to the atmospheric agents or to the alteration of the walls. Constitutes a major component of the shear strength if the walls are in contact.
A key parameter is the JRC (joint roughness coefficient) plotted as a function of the roughness of the joint's surface.
Material that separates the adjacent walls of a joint and that is usually less resistant than primitive rock. Typical filling materials are sand, silt, clay, more or less fine break, mylonite. It also includes thin layers of minerals and welded joint, for example, the veins of quartz and calcite.
The presence of filling material influences the behavior of the joint in respect of the mutual movement of the joint walls. In the survey is indicated the characteristic in reference to its hardness.
You can enter four values:
oAbsent
oCoherent
oIncoherent
oCement
Another useful parameter for the classification of the rock is the Ja ("Joint Alteration Number") which depends on the degree of alteration of the fractures, on the thickness and the nature of the filling. There are several types of alteration which correspond to the values of Ja.
In the ISRM Recommendation is added another index W that varies from 1 (bedrock or little altered) to 6 (extremely altered rock).
Data can be entered directly into the cells or paste data from a spreadsheet with the "Paste" function.
Individual or groups of rows can be deleted. After deleting data the graphical representation of the joints is automatically updated.
Moving the mouse over the diagram, in the status bar are shown the coordinates (immersion and inclination) of the point. If at the point clicked is shown a couple (dip direction, dip) of the joint, the corresponding line is highlighted in the input data grid.
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