Sir,please explain merits and demeris of joints from civil engineering projects point of view
Joints are favourable unfavourable in civil engineering-I have just given few examples now I am up grading in my book
Favourable structural, Sheet joints, vertical joints
In artificially exposed granite quarries sheeting is well exposed. In the field investigations of few granite quarries in Karnataka, Andhra Pradesh exhibit sheeting surfaces is curved and more or less parallel to the topographic surfaces. However in the regions of extensive and parallel erosion, the sheeting surface is not parallel to the topography .In few selective depth wise sheeting pattern analyses of granite quarries in Karnataka revealed that the visible sheeting pattern gradually not extended below the depth of about 3to 5m.However it differs depending upon the rock deposit and their extent of erosion .Few experts have suggested the invisible parallel sheeting pattern in granite rock deposits at greater depth influences workability .Sheet joints in commercial granite rock deposits minimizes the deployment of high cost of quarry equipment for bottom cutting
Presences of vertical joints in rock deposits are generally advantageous for quarry operators. A detailed field studies carried out in parts of Andhra Pradesh and Karnataka rock quarries suggested the advantage of vertical joints for exploitation. The study suggested vertical joint persist, facilitate for smooth splitting of rock deposit, minimum waste, high recovery (Kaniskan, 2004)
Dolerite (black granite) rock deposit worked with vertical-Joints in Warangal, Black granite-dolerite deposit and presented in the fig6.35.Verical joints favoured for workability in dolerite rock deposit(black granite)(Venkat Reddy,2013).Vertical joints are advantages and large stone blocks are extracted .
However the continuity of vertical joint pattern varies from deposit to deposit. A detailed field studies with selective test bore wells data requires to confirm the depth persist of vertical joints.
If the joint blocky joints –can be considered as blocky joints.If the depoosi exist moderate joints it comes under moderate joints.If the deposit persist highly joints listed under higly jointed.Recovery of deposit is inversely proportional to the density of joints in thre rock deposit.If the density of joints increases ,the recoverey of rock deposit reduces.However it is must to assess the extent of deep joint patrtern of the quarry/rock deposit for economic recoverey.(Kanishkan,2014)
Unfavourable structural discontinuities
Micro-joints in rocks are not directly visible to naked eye but could be seen in polished surfaces.
They develop due to release of stress minerals, or solar radiations .However it depends upon the rocks nature and local structural, geological conditions .systematic micro-petrographic analyses can delineate stress deposit free stress free rock deposit. These invisible discontinuities are much difficult to detect under normal geological investigations before mining. However latest techniques such as dye penetrates, ultrasonic velocity measurements ,load testing of selective core samples in different directions, micro-petrographic analysis for stress minerals etc may lead to detect invisible micro-discontinuities in commercial rock deposits(Venkat Reddy,2005)
Field analysis of joint pattern &workability of rock deposits- Field Analysis
Workability of Commercial granite rock deposit primarily depends upon the type, orientation, spacing and frequency of joint patterns.. In field observations revealed many quarry are not adopted technical/scientific aspects of joint patterns and their persistent
Workability of rock depots were adversely affected due to presence of joint sets and their orientation and persistence. Statistical data analysis requires the significance of existing joint systems, orientation and frequency of joints. Major lineaments of the region can be extracted using satellite imageries. Major lineaments will suggest general structural trends of the region. .Rock exploration requires to get all available traceable joint patterns and their trending directions-of the study area .Structural frequency diagrams-rose diagrams of the region have to prepare using structural data tools-Presently software’s are available for utilization and generation structural maps of the study area