Lecture 06 : Rock Properties & Testing-1

[Music] let me welcome you to the sixth lecture of drilling and blasting direction on this lecture we are going to quilt off rock homes and trying out this is the first lecture on this this lecture will continue to the subsequent lecture additionally so like each type what we do allow us to see retrospect our prior lectures in our previous lectures we understood the formation of earth now we have obvious the vital part of the earth is virtually in the liquid or semi-liquid stage then the stable part is the outer what and the rocks are shaped the solid part of the outer what so truly there are our crust is basically fashioned by using the rock we have now additionally understood the specific rock layers in the Earth’s crust and likewise we comprehend the definition of the rocks mineral etcetera within the final class and at this factor we are in a position to read the affect of unique physical and mechanical residences of rocks certainly at the same time we are seeking to have an understanding of the drilling operation so as in the introduction category we’ve understood the drilling is carried out within the rock in order that we will location explosive within the incorrect to blast it so how one of a kind rock substances the rock residences are clearly influencing the performance of a drill efficiency of the drill desktop performance of the drill tool we’re trying to recognize these matters in these lectures so our studying pursuits are to know the one of a kind influential physical Rock homes to know the distinct influential mechanical Rock houses and we have got to comprehend methods to measure these properties of rock so we are looking to appreciate this let us see what are the one of a kind influential Rock properties that are affecting the performance of a drill computing device the primary predominant one which is basically basically influencing the efficiency of a drill is the force then the hardness elasticity plasticity abrasive ‘ti texture structure and traits of breakage amongst these obviously the principal one which is influencing is the force and basically the leisure are more or less involving each different say abrasiveness hardness texture constructions these are interrelated and these are having gigantic have an impact on now not most effective on the efficiency of the drill machines in that certain Rock but also the economics of the drilling is kind of relying on these so this all these parameters are having giant have an impact on and we’ll speak about how they’re influencing the efficiency of the drilling but right now we’re in view that concerning the definitions and the process of the exams so first allow us to bear in mind in regards to the strength houses actually in this lecture we will be able to duvet most effective the strange properties relaxation different properties we will be able to discussed in the subsequent lectures so first the do not forget the strength homes essentially strength property is the mechanical force of a rock is the property of opposing destruction by way of an external drive either static or dynamic so this is very main the style of force it may be static it could be static it could be dynamic so the force of a rock is that a lot at what drive or what stress the rock is subjected to fell so mechanical force of the rock is essentially outlined by using the highest stress that’s face up to by way of that rock specimen subjected to a static loading or to a dynamic loading clearly the difference between static and dynamic loading is relying on the loading rate that implies how rapid we’re increasing the fee of loading that is truly differentiating the static and dynamic loading however presently the entire mechanical testing is being implemented or the static loading and they are the dynamic loading may be very diversified in laboratory scale producing a dynamic loading setup may be very very difficult thats why dynamic strengths are being assessed via oblique system to not the direct method so basically all the dimension of force which we’ll speak about in this lecture or the static size so the missile strength whenever we’re talking in regards to the force it is at all times understood that this is the static strength of that rock it can be either in compression or in CR or in tensile and we will be able to talk about how these are distance can be distinguished however at this factor let us know that the maximum Rock gives maximum resistance to compression and least resistance in case of tensile that suggests if a specimen is tried to be pulled away by taking its two part the force requirement shall be minimal but when we try to ruin it through compressing this to by way of to finish it it’s the resistance it will so the highest so you will see that the highest resistance is underneath compression minimal least resistance Iran is under tensile correctly it’s virtually one tenth or one twelfth time of the compressive stress and this is occurred traditionally as a result of the failure of the rocks to the enormous number of the neighborhood safeguard and his irregularities basically a rock is a mat is a material which so almost a toxic tree of about 0.2 0.1 zero.5 zero.1 five factor two point two factor 5 like that and a rock force basically depends on the mineralogical compositions and among the many integrating minerals quads is the most stable with a force that goes over 500 mega Pascal and ferromagnet magnesium silicates and the alumina silicates fluctuate between 200 to 500 MPA Cal sites are virtually the vulnerable rocks and coal can be very very weak rock so basically you will see that the compressive force of the rocks various almost lower than 1 to 500 mega Pascal that suggests from very very delicate to very very robust rock stipulations truly that measures the integrity of the rock rock force also will depend on the mineral no longer simplest within the mineralogical compositions but also they’re formations if you happen to regularly will to find the rock formed under volcanic eruptions underneath excessive temperature strain that customarily source high rock strength than the rock formation in some sedimentation or etcetera so like this a rock strength relies on the rock formation relies on the mineralogical characters is dependent upon the integrated geological disturbances within the sample so it will depend on a quantity of reasons but let us see what are the one of a kind uncooked strength experiment we carry out more often than not in our lab we classify our strength under compressive below tension and beneath CR so that is the compressive when is permit the rock specimen to be sub J under a compressive load and notice the fail the load at which the rock fails is considered because the compressive force compressive force and if we subject it to a anxiety then it’s called tensile force but see r1 is little bit complex we carry out shear test either a direct shear scan or by means of the Trachsel scan we try to find out the shear strength of the rock the place prime part of the specimen is subjected to a load below this course the bottom section is subjected to a load below disk this course and we attempt to notice the shear alongside this plane of the fabric so that is the shear away we try to discover the shear strength of the specimen so truly compressive force training compressive force in the laboratory could be very very handy however doing this to our little bit intricate and mostly that is why we go for the oblique testing ways for this so that we are able to have some these values however by way of every other manner so for compressive testing we are in most cases perform point load scan uniaxial compressive experiment and likewise tri-axial compressive scan so these are the equipment that is the point load equipment where the conical ends are there below which the rock specimen is subjected to below loading right here a typical specimen is subjected to load below a uniaxial compressive chamber and interaxial we enable the lateral strain fixed lateral pressure while the specimen is specimen is allowed to be loaded under a compressive load the diversities amongst these three is that in point load scan we are able to query out point no longer testing in the irregular sample also the testing approach may be very handy pattern specification requirement is less that is why gigantic number of specimen may also be demonstrated which gives a quite just right outcomes to relate this effect with the compressive test comm precipitates the crisis is the training of the sample this pattern practise is little bit problematical the place n number of cares must be taken on the smoothness of the sample dimension of the samples linearity of the samples so this spacing this care will have to be taken previous to accomplishing the scan of the pattern in a similar way in trachsel also pattern specimen is a specimen pattern preparation is intricate after that the scan approach is also difficult the place the tri-axial load has to be hydrolytically supplied utilizing some external means so because of this this tri-axial mobilephone needs to be pretty much required to carry out the Trachsel test under the identical uniaxial compressive checking out computer so that is the point load test the place the specimen is used to assess the uniaxial compressive test and rock specimen is in the type of core sample or may be the cut blocks despite the fact that irregular lumps are also taken for carrying out the factor load to undertaking the point load scan right here the samples are samples are positioned under the conical platen and the space between the specimen of the platters is recorded so this is the preliminary record then this recorded one viewed as this one this is this recorded distance and then the load is regularly improved failure load is loaded so failure load this is the P is the weight and dividing it by the distance of the initial power conical platen distance that square of that it offers us the point load index for irregular pattern if we go for diametrical loading of the core pattern then is the similar core diameter or if any specimen which is placed here that’s the identical so within the in case of standard specimen it is loaded axially not within the diametrical II so it is axially loaded on the usual experiment with D is equal to L loading in that case that’s called I failed to establish that’s the ordinary loading of the point load experiment but point load experiment may also be implemented irregular samples due to the fact that it is very very main the equal sample indicates one of a kind values of force when it’s loaded in special guidelines so this is why point load testing may be very very fundamental factor load index may also be directly associated with the uniaxial compressive strength we can talk about that at a latter part allow us to see this video which is giving us the – which is first-rate the scan so each and every experiment is used to do to me and classify the strength index of rocks you can find here i have a scepter which is ma bow this sample has been dealt with to targeted dimensions it’s a diameter of these samples and this facet is the length of the samples so the ratio of the pattern is 1 to 1 hike to the meter the test start with marking the middle factor of the pattern through using a pencil and ruler in finding the midpoint of the top sample founded on this causation line and win the same factor to the bottom one this is primary with the intention to get a good outcome and through mode of failure then location this unsuitable pattern in between the keep edge and you can find right here bottom and top side then give slightly pressure so that the pattern is appropriately located and are not able to transfer anyplace after that set the gauge studying to zero generally the items use is a single unit which is Newton’s then proceed the test through develop the weight and you’ll fill the dish route getting harder and more difficult until the pattern fill and as you’ll find now the pattern is already filled and wreck aside and finally take the studying of maximum factor load recorded in gauge so which you can observe how the point load experiment is being carried out point load experiment can also be correlated with the uniaxial compressive scan for the self like coal missile rock if point load index can also be multiplied with the 24 to get a uniaxial compressive test this kind this constants are in actual fact calculated through the statistical analysis and sincerely factor loading index is instantly linearly correlated with the uniaxial compressive price so these are the feasible experiment that is why point load may be very very effortless and could exchange uniaxial compressive test whether it is carried out in a good quantity of samples let us now see what is uniaxial compressive scan unit mobilephone compressive test is the direct dimension of the rock compressive force in this experiment cylindrical rock specimens are rock specimens are proven with L by D ratio of 2 to 2.5 it must be flat it must be tender and parallel lens need to be there so there should no longer be any eccentric metropolis of the sample foil it’s the loading is being implemented and their tolerance limits are already given in isolation requirements HTM standards that must be adopted at the same time that experiment is being implemented on this test that you could say that is the one video of the test on this test you’ll find the loading is being applied come for a compressive experiment sample so this pattern is placed there’s no eccentricity the plates are parallel to one another whilst it’s underneath loading and step by step with a fixed loading expense the weight is being multiplied on the pattern 250 [Music] 16:17 improved complement to the Rockville 8090 300 [Music] and yep he goes proper there [Music] suddenly the burden is released from the sample so that is the so that is the specimen which is subjected to a compressive load and the compressive force can be assessed with the aid of utilizing the system P is the same as strength is equal to P via F the place P is the failure load failure load is the subject go sectional discipline of the specimen so on this case the loading is given uniaxial ii the loading in different two guidelines will not be on hand so the common loading is that this one and specimen is subjected to load so that is the string can be conveniently calculated utilising this this is the radial strain and that is the axial stress and for those who plot the curve between stress and strain you’ll find out the failure is like this so there is a sudden failure of the fabric if it the material is brittle in this position so this is customary traits of a compressive checking out tensile checking out is in actual fact applied the place direct tensile checking out shouldn’t be at all times feasible so in direct tensile trying out is implemented in Brazilian scan sample in Brazilian scan sample where the specimen is positioned specimen is placed like this and it is loaded radially so what is occurred although the loading is given compressive but the specimen fails on that plane where the forces are acting in a tensile direction so for this reason this force parameter is truly discovered is the – is the tensile force no longer the compressive strength so Brazilian tensile scan is in actual fact an indirect tensile strength size process where the in direct tensile CR of the intact rock core is carried out so in this test core specimen with L by way of D ratio with L via D ratio it’s errors are there half is taken L with the aid of D ratio of 1/2 is taken under compressive loading desktop and it is platen sir diametrically placed domestically throughout the specimen so that is the platen flattens are positioned diametrically across the specimen and the load maximum load to fracture the specimen is recorded and the tensile force is computed as Sigma T is equal to 2 P via PI D T the place T is the thickness the place T is the thickness that suggests the length of the sample D is the diameter of the sample and P is the so sincerely this is the p is the failure load that is the method to provide us the tensile strength of the rock specimen so allow us to discover let us discover one such video to be had in the YouTube for the tensile strength measurement of some concrete specimen so here the great thing about this video is that in this video that you can discover this in a sluggish p.C. Additionally it reminded in a slow area so that is the cylindrical pattern of prepared with common Portland cement and you will find the actual-time video of 25 FPS of this failure so as the specimen is subjected to load you can find the tensile cracks are created throughout the diameter and the specimen fails under tension so that is the slow percent you will see the propagation of the cracks in the specimen propagation of the cracks in the pacing specimen you will see the cracks are being widened gradually and finally the specimen fells so this is the vertical load versus vertical displacement graph so that is the direct shear test customarily tensile failure could be very rarely occur in the rock as a rule we provide the compressive load on to the rock and rock fills underneath compression however generally rock fails below anxiety also whilst we can talk about concerning the tensile slamming zone of the blasting they are the rock fells on the anxiety the difference between compressive failure and tensile failure is that once Rock fails underneath compression it disintegrated right into a number of portions the place it fails beneath tension it disintegrates into most effective two pieces now not a quantity of portions so truly tensile failure offers us a protracted crack whilst compressive failure gives the in number of smaller fragmented material so that is why compressive failure the power is that it’s compressive load can be with ease given onto the fabric and it is complicated to furnish the tensile load onto the material nevertheless compressive strength is highest for the rock tensile force is the minimum of the rock so the tensile force of the rock is minimal then additionally it’s not customarily practiced when you consider that that providing a tensile load onto the material is intricate so hammering etcetera all these are the failure of fabric under compressive load now not the tensile load so essentially in between this two strength there’s the shear strength the overall values of stress shear force of the rock is lesser than the compressive strength however higher than the tensile strength rock fails under sea are also frequently rock fails beneath shear most of the times for the reason that of the shear in number of masses are performing on the rock in on in-situ condition and that is making a shear loading on rock as commonly it is occur when you consider that of the heterogeneity of the the direct shear is measured on the direct shear scan equipment nonetheless direct shear test equipment is applicable for the unfastened material for the delicate material handiest for the reason that in any other case it this can not be utilized so in direct shear experiment there’s a this shear force is set the characteristics of rock along the aircraft of weak point the specimen is positioned within the cut back half of of the shear field and encapsulated in either synthetic artificial resin or mortar the specimen ought to be placed so that the line of action of the shear drive lies in the airplane of the discontinuity to be investigated and the normal drive acts perpendicular to the to this floor so was the encapsulated fabric encapsulated material has hardened the specimen is set up in the higher 1/2 of the shear box in the same manner a strip roughly 5 mm large above and beneath the sheer surface need to be saved freed from encapsulating fabric the test is then implemented through making use of a horizontal shear force T under a constant natural load so that is the foremost requirement that it must be carried out in a common normal load now you will see that this video where the direct shear is being carried out of a unfastened material sand material so this is to verify the shear force this is the direct shear operators these are the loading pad perforated plates etcetera this is the owing desktop to use the best way the material lose material so sandy soil fabric is taken of constant quantity then the shear field is set that is the shear field then first the retaining plate has to be offered then the perforated plate or solid grid pair plate then the material will be placed on that then the material will probably be compacted in order that the above perforated plate changed will likely be positioned on this then the upper plate might be placed on this now the loading plaid sample be placed on that then the usual load is which is under placing condition might be placed on this now the desired common load may be suspended from this plate so these are the typical fixes for fixing the common load then the horizontal force will take delivery of from the you hydraulically operated motors and the failure load might be recorded so this is the direct shear experiment can be carried out on the pattern so allow us to discontinue at this role from this for this lecture we will be able to continue to peer the affect of other houses within the next classification thanks

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