Lecture 06 : Rock Properties & Testing-1

[Music] let me welcome you to the sixth lecture of drilling and blasting path in this lecture we will duvet off rock houses and checking out that is the primary lecture on this this lecture will continue to the subsequent lecture also so like every classification what we do allow us to see retrospect our previous lectures in our prior lectures we understood the formation of earth now we have seen the crucial a part of the earth is just about in the liquid or semi-liquid stage then the stable section is the outer what and the rocks are formed the strong a part of the outer what so clearly there are our crust is in actual fact fashioned by way of the rock we’ve got additionally understood the distinctive rock layers within the Earth’s crust and in addition we have an understanding of the definition of the rocks mineral etcetera within the last classification and at this point we are equipped to read the affect of special bodily and mechanical homes of rocks primarily while we’re looking to comprehend the drilling operation so as in the introduction type now we have understood the drilling is applied in the rock in order that we are able to place explosive inside the fallacious to blast it so how special rock materials the rock homes are clearly influencing the performance of a drill performance of the drill machine performance of the drill software we’re looking to realise these things in these lectures so our finding out objectives are to understand the distinctive influential physical Rock properties to know the exceptional influential mechanical Rock homes and we have to fully grasp how you can measure these homes of rock so we are looking to fully grasp this allow us to see what are the distinctive influential Rock residences that are affecting the performance of a drill computer the first predominant one which is basically mainly influencing the efficiency of a drill is the force then the hardness elasticity plasticity abrasive ‘ti texture constitution and characteristics of breakage amongst these definitely the fundamental one which is influencing is the force and in actual fact the relaxation are kind of regarding every different say abrasiveness hardness texture constructions these are interrelated and these are having huge impact now not handiest on the performance of the drill machines in that targeted Rock but in addition the economics of the drilling is kind of relying on these so this all these parameters are having significant affect and we’ll talk about how they are influencing the efficiency of the drilling however right now we are for the reason that in regards to the definitions and the procedure of the exams so first allow us to keep in mind concerning the force properties correctly in this lecture we will quilt only the unusual residences relaxation other properties we can discussed in the subsequent lectures so first the recall the strength residences basically strength property is the mechanical force of a rock is the property of opposing destruction by using an outside force either static or dynamic so that is very major the style of force it may be static it can be static it can be dynamic so the strength 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 truly defined via the maximum stress that’s stand up to through that rock specimen subjected to a static loading or to a dynamic loading truly the difference between static and dynamic loading is depending on the loading cost that means how fast we are growing the fee of loading that is clearly differentiating the static and dynamic loading nevertheless 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 generating a dynamic loading setup may be very very complex thats why dynamic strengths are being assessed through indirect approach to not the direct system so basically all of the dimension of strength which we are going to discuss on this lecture or the static dimension so the missile strength whenever we are speaking about the strength it’s constantly understood that that is the static force of that rock it could be either in compression or in CR or in tensile and we will be able to speak about how these are distance may also be individual but at this factor tell us that the maximum Rock gives maximum resistance to compression and least resistance in case of tensile that implies if a specimen is tried to be pulled away with the aid of taking its two phase the force requirement shall be minimum but if we try to smash it by way of compressing this to through to end it it is the resistance it is going to so the highest so you’ll discover the maximum resistance is beneath compression minimum least resistance Iran is underneath tensile actually it is virtually one tenth or one twelfth time of the compressive stress and this is occurred probably because of the failure of the rocks to the massive quantity of the local defense and his irregularities basically a rock is a mat is a fabric which so close to a poisonous tree of about 0.2 zero.1 0.5 0.1 5 factor two point two factor five like that and a rock strength basically depends upon the mineralogical compositions and among the many integrating minerals quads is essentially the most stable with a strength that goes over 500 mega Pascal and ferromagnet magnesium silicates and the alumina silicates differ between 200 to 500 MPA Cal web sites are almost the weak rocks and coal can be very very vulnerable rock so essentially you will find the compressive force of the rocks varying practically lower than 1 to 500 mega Pascal that suggests from very very delicate to very very robust rock conditions basically that measures the integrity of the rock rock strength additionally relies on the mineral now not simplest within the mineralogical compositions but in addition they are formations should you generally will to find the rock formed below volcanic eruptions beneath high temperature stress that traditionally supply excessive rock force than the rock formation in some sedimentation or etcetera so like this a rock force depends upon the rock formation will depend on the mineralogical characters is dependent upon the integrated geological disturbances in the sample so it is determined by a number of explanations however let us see what are the one of a kind uncooked strength experiment we feature out most commonly in our lab we classify our force underneath compressive below anxiety and below CR so that is the compressive when is allow the rock specimen to be sub J beneath a compressive load and spot the fail the burden at which the rock fails is considered as the compressive force compressive strength and if we field it to a tension then it is referred to as tensile force however see r1 is little bit elaborate we supply out shear experiment either an instantaneous shear test or by means of the Trachsel scan we try to find out the shear force of the rock where top a part of the specimen is subjected to a load below this path the bottom phase is subjected to a load beneath disk this direction and we attempt to observe the shear along this airplane of the material so that is the shear away we attempt to discover the shear force of the specimen so truly compressive strength training compressive strength within the laboratory may be very very effortless however doing this to our little bit elaborate and customarily that is why we go for the oblique checking out methods for this so that we are able to have some these values however by means of any other means so for compressive checking out we are as a rule perform factor load scan uniaxial compressive test and also tri-axial compressive scan so these are the equipment that is the point load apparatus where the conical ends are there underneath which the rock specimen is subjected to under loading here a normal specimen is subjected to load under a uniaxial compressive chamber and interaxial we enable the lateral pressure constant lateral strain whilst the specimen is specimen is allowed to be loaded under a compressive load the differences among these three is that in factor load experiment we will query out factor no longer testing within the irregular sample also the trying out method is very easy pattern specification requirement is less because of this big number of specimen can also be proven which offers a rather excellent outcomes to narrate this result with the compressive experiment comm precipitates the difficulty is the training of the pattern this pattern preparation is little bit challenging where n quantity of cares must be taken on the smoothness of the pattern dimension of the samples linearity of the samples so this spacing this care will have to be taken prior to accomplishing the scan of the sample in a similar fashion in trachsel additionally pattern specimen is a specimen pattern instruction is problematic after that the scan method is also elaborate where the tri-axial load must be hydrolytically offered using some external manner so this is why this tri-axial telephone needs to be basically required to hold out the Trachsel scan under the identical uniaxial compressive trying out machine so that is the point load scan the place the specimen is used to evaluate the uniaxial compressive test and rock specimen is in the form of core pattern or is also the reduce blocks even if irregular lumps are also taken for conducting the point load to undertaking the factor load scan here the samples are samples are positioned below the conical platen and the space between the specimen of the platters is recorded so this is the initial report then this recorded one considered as this one this is this recorded distance after which the load is often improved failure load is loaded so failure load this is the P is the burden and dividing it through the gap of the initial chronic conical platen distance that rectangular of that it gives us the factor load index for irregular pattern if we go for diametrical loading of the core sample then is the equivalent core diameter or if any specimen which is placed here that’s the identical so in the in case of commonplace specimen it is loaded axially now not within the diametrical II so it’s axially loaded on the ordinary test with D is equal to L loading in that case that is known as I failed to identify that is the ordinary loading of the point load experiment but point load experiment can also be carried out irregular samples due to the fact that it is vitally very important the same pattern indicates one-of-a-kind values of strength when it is loaded in extraordinary guidelines so that is why factor load checking out could be very very fundamental point load index will also be straight related with the uniaxial compressive force we will be able to discuss that at a latter phase let us see this video which is giving us the – which is best the experiment so each experiment is used to do to me and classify the strength index of rocks you can see right here i have a scepter which is ma bow this sample has been dealt with to particular dimensions it is a diameter of those samples and this aspect is the length of the samples so the ratio of the pattern is 1 to 1 hike to the meter the scan with marking the center factor of the sample with the aid of using a pencil and ruler in finding the midpoint of the highest sample established on this causation line and win the equal factor to the bottom one this is foremost as a way to get a excellent outcomes and via mode of failure then location this fallacious pattern in between the retailer part and you will see that here bottom and top part then supply a little bit pressure in order that the pattern is competently placed and are not able to transfer anyplace after that set the gauge reading to zero typically the models use is a single unit which is Newton’s then continue the experiment with the aid of broaden the load and you will fill the dish route getting harder and harder until the sample fill and as you can see now the sample is already stuffed and break apart and finally take the studying of highest factor load recorded in gauge so which you can discover how the factor load experiment is being applied factor load experiment will also be correlated with the uniaxial compressive test for the self like coal missile rock if factor load index will also be multiplied with the 24 to get a uniaxial compressive scan this sort this constants are truly calculated via the statistical evaluation and essentially point loading index is immediately linearly correlated with the uniaxial compressive value so these are the feasible experiment that is why point load could be very very convenient and may just replace uniaxial compressive scan if it is implemented in a just right quantity of samples allow us to now see what is uniaxial compressive experiment unit telephone compressive scan is the direct dimension of the rock compressive strength on this experiment cylindrical rock specimens are rock specimens are validated with L through D ratio of 2 to 2.5 it ought to be flat it have got to be delicate and parallel lens have to be there so there will have to not be any eccentric metropolis of the pattern foil it is the loading is being applied and their tolerance limits are already given in isolation specifications HTM specifications that have got to be followed while that scan is being carried out in this scan that you can say that is the one video of the experiment in this experiment you will discover the loading is being implemented come for a compressive test pattern so this sample is placed there is not any eccentricity the plates are parallel to one another while it is below loading and steadily with a constant loading rate the load is being elevated on the pattern 250 [Music] sixteen:17 improved complement to the Rockville 8090 300 [Music] and yep he goes correct there [Music] suddenly the load is launched from the pattern so this is the so this is the specimen which is subjected to a compressive load and the compressive force can be assessed by using utilising the formula P is equal to strength is equal to P through F where P is the failure load failure load is the subject pass sectional field of the specimen so on this case the loading is given uniaxial ii the loading in different two instructional materials just isn’t available so the common loading is that this one and specimen is subjected to load so that is the string may also be without difficulty calculated using this that is the radial strain and that is the axial strain and if you plot the curve between stress and stress you’re going to discover the failure is like this so there’s a surprising failure of the fabric if it the fabric is brittle on this location so this is long-established characteristics of a compressive trying out tensile checking out is basically carried out the place direct tensile checking out will not be always viable so in direct tensile trying out is applied in Brazilian test sample in Brazilian scan sample the place the specimen is placed specimen is placed like this and it’s loaded radially so what is happened although the loading is given compressive however the specimen fails on that aircraft where the forces are appearing in a tensile path so because of this this force parameter is in actual fact found is the – is the tensile strength no longer the compressive strength so Brazilian tensile scan is sincerely an oblique tensile force measurement system the place the in direct tensile CR of the intact rock core is implemented so on this scan core specimen with L by using D ratio with L with the aid of D ratio it’s mistakes are there 1/2 is taken L with the aid of D ratio of half is taken underneath compressive loading laptop and it is platen sir diametrically placed domestically across the specimen so that is the platen flattens are placed diametrically across the specimen and the load highest load to fracture the specimen is recorded and the tensile force is computed as Sigma T is the same as 2 P with the aid of PI D T the place T is the thickness the place T is the thickness that suggests the size of the sample D is the diameter of the pattern and P is the so essentially this is the p is the failure load this is the system to present us the tensile strength of the rock specimen so allow us to become aware of let us notice one such video available in the YouTube for the tensile force dimension of some concrete specimen so here the fantastic thing about this video is that in this video you could discover this in a gradual p.C. Also it reminded in a sluggish space so that is the cylindrical sample of all set with typical Portland cement and you’ll find the real-time video of 25 FPS of this failure in order the specimen is subjected to load you can see the tensile cracks are created across the diameter and the specimen fails under tension so this is the slow percent you’ll find the propagation of the cracks within the specimen propagation of the cracks within the pacing specimen you can find the cracks are being widened steadily and ultimately the specimen fells so this is the vertical load versus vertical displacement graph so that is the direct shear test most likely tensile failure is very not often arise within the rock as a rule we provide the compressive load on to the rock and rock fills under compression however many times rock fails below anxiety additionally while we will discuss about the tensile slamming zone of the blasting they’re the rock fells on the anxiety the difference between compressive failure and tensile failure is that after Rock fails beneath compression it disintegrated into a number of pieces the place it fails below anxiety it disintegrates into best two portions no longer a number of pieces so sincerely tensile failure offers us a protracted crack while compressive failure gives the in number of smaller fragmented fabric so this is the reason compressive failure the power is that it is compressive load can also be effortlessly given onto the material and it’s difficult to furnish the tensile load onto the material nonetheless compressive strength is highest for the rock tensile strength is the minimal of the rock so the tensile strength of the rock is minimum then additionally it’s not in most cases practiced due to the fact that that delivering a tensile load onto the fabric is intricate so hammering etcetera all these are the failure of fabric underneath compressive load not the tensile load so essentially in between this two force there’s the shear force the general values of stress shear strength of the rock is lesser than the compressive strength but bigger than the tensile strength rock fails under sea are also routinely rock fails underneath shear lots of the times seeing that of the shear in number of loads are performing on the rock in on in-situ condition and that’s creating a shear loading on rock as regularly it is occur since of the heterogeneity of the the direct shear is measured on the direct shear scan equipment however direct shear test equipment is applicable for the unfastened fabric for the smooth material only in view that or else it this are not able to be utilized so in direct shear scan there’s a this shear force is decided the traits of rock alongside the plane of weak spot the specimen is positioned within the scale down half of of the shear box and encapsulated in either artificial synthetic resin or mortar the specimen must be positioned in order that the road of motion of the shear drive lies in the plane of the discontinuity to be investigated and the average force acts perpendicular to the to this surface so used to be the encapsulated material encapsulated fabric has hardened the specimen is hooked up in the higher half of the shear field in the identical method a strip roughly 5 mm extensive above and under the sheer surface must be saved freed from encapsulating fabric the scan is then applied by way of making use of a horizontal shear force T under a steady average load so this is the primary requirement that it have got to be carried out in a ordinary typical load now you’ll discover this video where the direct shear is being carried out of a loose fabric sand material so this is to investigate the shear force this is the direct shear operators these are the loading pad perforated plates etcetera this is the owing machine to use the best way the material lose material so sandy soil material is taken of fixed wide variety then the shear field is set this is the shear field then first the conserving plate needs to be furnished then the perforated plate or solid grid pair plate then the fabric might be placed on that then the fabric will likely be compacted in order that the above perforated plate replaced will likely be placed on this then the upper plate shall be placed on this now the loading plaid pattern be placed on that then the average load is which is below placing might be positioned on this now the favored ordinary load may be suspended from this plate so these are the ordinary fixes for fixing the common load then the horizontal drive will be given from the you hydraulically operated motors and the failure load will likely be recorded so this is the direct shear experiment can also be applied on the pattern so let us discontinue at this function from this for this lecture we can proceed to see the have an impact on of alternative residences in the next category thank you

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