Lecture 06 : Rock Properties & Testing-1

[Music] let me welcome you to the sixth lecture of drilling and blasting direction in this lecture we will duvet off rock houses and testing that is the first lecture on this this lecture will continue to the next lecture also so like every type what we do allow us to see retrospect our previous lectures in our previous lectures we understood the formation of earth now we have obvious the principal part of the earth is virtually in the liquid or semi-liquid stage then the solid section is the outer what and the rocks are formed the strong a part of the outer what so sincerely there are our crust is in actual fact shaped via the rock now we have also understood the distinctive rock layers in the Earth’s crust and likewise we appreciate the definition of the rocks mineral etcetera within the last type and at this point we are competent to learn the impact of specific bodily and mechanical homes of rocks above all at the same time we are trying to appreciate the drilling operation so as in the introduction category we have understood the drilling is applied within the rock in order that we can location explosive throughout the improper to blast it so how exclusive rock substances the rock properties are basically influencing the efficiency of a drill efficiency of the drill machine efficiency of the drill tool we are trying to realize these things in these lectures so our studying targets are to understand the specific influential physical Rock residences to understand the distinctive influential mechanical Rock homes and we must recognize the best way to measure these residences of rock so we’re seeking to realise this let us see what are the unique influential Rock properties which can be affecting the performance of a drill laptop the primary predominant one which is essentially principally influencing the performance of a drill is the force then the hardness elasticity plasticity abrasive ‘ti texture constitution and traits of breakage amongst these certainly the most important one which is influencing is the force and in actual fact the rest are roughly involving every other say abrasiveness hardness texture structures these are interrelated and these are having large have an impact on no longer simplest on the efficiency of the drill machines in that detailed Rock but also the economics of the drilling is kind of depending on these so this all these parameters are having large have an impact on and we’ll discuss how they’re influencing the efficiency of the drilling but at the moment we are considering that in regards to the definitions and the procedure of the tests so first let us don’t forget in regards to the force residences actually on this lecture we can cover simplest the unusual properties leisure other houses we can mentioned within the subsequent lectures so first the remember the force houses in actual fact strength property is the mechanical strength of a rock is the property of opposing destruction with the aid of an external force both static or dynamic so this is very foremost the style of force it could be static it could be static it may be dynamic so the strength of a rock is that so much at what drive or what stress the rock is subjected to fell so mechanical strength of the rock is in actual fact outlined by using the maximum stress that is withstand with the aid of that rock specimen subjected to a static loading or to a dynamic loading basically the change between static and dynamic loading is relying on the loading price that means how quick we are growing the cost of loading that’s basically differentiating the static and dynamic loading however right now all the mechanical checking out is being carried out or the static loading and they’re the dynamic loading may be very varied in laboratory scale generating a dynamic loading setup is very very complex thats why dynamic strengths are being assessed through indirect procedure to not the direct process so sincerely all of the measurement of strength which we’ll discuss on this lecture or the static dimension so the missile strength at any time when we are speakme in regards to the force it is invariably understood that that is the static force of that rock it is usually either in compression or in CR or in tensile and we will discuss how these are distance can also be exotic however at this point tell us that the maximum Rock gives highest resistance to compression and least resistance in case of tensile that means if a specimen is tried to be pulled away by using taking its two section the strength requirement will be minimal but when we attempt to spoil it by compressing this to by way of to finish it it’s the resistance it’s going to so the maximum so you will see the maximum resistance is under compression minimum least resistance Iran is under tensile in fact it’s close to one tenth or one twelfth time of the compressive stress and this is occurred mainly because of the failure of the rocks to the huge range of the local security and his irregularities sincerely a rock is a mat is a material which so close to a toxic tree of about 0.2 0.1 0.5 0.1 5 factor two factor two point five like that and a rock strength essentially is dependent upon the mineralogical compositions and among the many integrating minerals quads is essentially the most strong with a force that goes over 500 mega Pascal and ferromagnet magnesium silicates and the alumina silicates vary between 200 to 500 MPA Cal sites are practically the weak rocks and coal is also very very vulnerable rock so essentially you’ll discover the compressive force of the rocks varying almost less than 1 to 500 mega Pascal that suggests from very very gentle to very very strong rock conditions basically that measures the integrity of the rock rock strength also depends on the mineral now not most effective in the mineralogical compositions but additionally they’re formations should you probably will in finding the rock formed underneath volcanic eruptions below high temperature pressure that regularly source high rock strength than the rock formation in some sedimentation or etcetera so like this a rock strength will depend on the rock formation is determined by the mineralogical characters depends upon the built-in geological disturbances within the sample so it depends upon a quantity of motives however let us see what are the unique uncooked strength test we feature out commonly in our lab we classify our force beneath compressive under anxiety and underneath CR so that is the compressive when is permit the rock specimen to be sub J underneath a compressive load and spot the fail the weight at which the rock fails is considered as the compressive force compressive strength and if we subject it to a anxiety then it is called tensile force but see r1 is little bit difficult we stock out shear scan either a direct shear scan or via the Trachsel test we attempt to discover the shear strength of the rock the place top a part of the specimen is subjected to a load underneath this path the bottom phase is subjected to a load beneath disk this direction and we try to discover the shear along this aircraft of the fabric so that is the shear away we attempt to discover the shear force of the specimen so sincerely compressive strength practising compressive force in the laboratory is very very easy however doing this to our little bit intricate and most commonly because of this we go for the indirect checking out methods for this so that we are able to have some these values but by means of every other method so for compressive checking out we are by and large perform point load experiment uniaxial compressive test and also tri-axial compressive experiment so these are the apparatus that is the factor load equipment the place the conical ends are there underneath which the rock specimen is subjected to underneath loading right here a ordinary specimen is subjected to load beneath a uniaxial compressive chamber and interaxial we allow the lateral pressure fixed lateral strain whilst the specimen is specimen is allowed to be loaded below a compressive load the variations among these three is that in factor load experiment we can query out factor now not checking out in the irregular sample additionally the testing approach is very effortless pattern specification requirement is much less for this reason massive number of specimen can also be confirmed which offers a fairly good outcomes to narrate this outcomes with the compressive test comm precipitates the concern is the instruction of the sample this pattern training is little bit complex the place n number of cares needs to be taken on the smoothness of the pattern dimension of the samples linearity of the samples so this spacing this care should be taken prior to engaging in the test of the pattern in a similar way in trachsel additionally sample specimen is a specimen pattern instruction is tricky after that the scan system can be tricky where the tri-axial load needs to be hydrolytically offered utilising some external manner so for this reason this tri-axial cell has to be basically required to hold out the Trachsel experiment below the equal uniaxial compressive checking out computing device so this is the point load experiment where the specimen is used to assess the uniaxial compressive test and rock specimen is in the form of core pattern or is also the cut blocks even if irregular lumps are also taken for accomplishing the point load to carrying out the factor load test here the samples are samples are positioned under the conical platen and the space between the specimen of the platters is recorded so that is the initial report then this recorded one regarded as this one that is this recorded distance and then the load is frequently elevated failure load is loaded so failure load that is the P is the weight and dividing it by the gap of the initial persistent conical platen distance that square of that it gives us the point load index for irregular sample if we go for diametrical loading of the core pattern then is the identical core diameter or if any specimen which is placed right here that is the identical so in the in case of normal specimen it’s loaded axially now not within the diametrical II so it is axially loaded on the commonplace scan with D is the same as L loading in that case that’s referred to as I failed to establish that is the regular loading of the factor load scan but factor load experiment can be carried out irregular samples when you consider that it is extremely very main the equal sample suggests exclusive values of force when it is loaded in extraordinary guidelines so this is the reason point load testing could be very very major factor load index will also be directly associated with the uniaxial compressive force we can speak about that at a latter phase allow us to see this video which is giving us the – which is satisfactory the experiment so each experiment is used to do to me and classify the strength index of rocks you’ll find here i’ve a scepter which is ma bow this sample has been treated to distinctive dimensions it is a diameter of those samples and this facet is the length of the samples so the ratio of the sample is 1 to 1 hike to the meter the scan start with marking the core point of the pattern via using a pencil and ruler find the midpoint of the top sample based on this causation line and win the equal thing to the bottom one that is main in an effort to get a just right influence and by way of mode of failure then position this improper pattern in between the store side and you will see that here backside and top part then provide a little bit stress so that the pattern is adequately located and are not able to transfer anyplace after that set the gauge studying to zero most often the models use is a single unit which is Newton’s then continue the test via expand the load and you will fill the dish route getting tougher and harder until the pattern fill and as you will find now the pattern is already crammed and destroy aside and finally take the studying of highest point load recorded in gauge so which you could discover how the factor load experiment is being carried out factor load experiment may also be correlated with the uniaxial compressive experiment for the self like coal missile rock if factor load index may also be increased with the 24 to get a uniaxial compressive experiment this sort this constants are basically calculated by means of the statistical analysis and truly point loading index is immediately linearly correlated with the uniaxial compressive worth so these are the viable experiment that is why factor load is very very easy and could change uniaxial compressive test if it is carried out in a good quantity of samples let us now see what is uniaxial compressive scan unit mobilephone compressive experiment is the direct size of the rock compressive strength on this experiment cylindrical rock specimens are rock specimens are demonstrated with L by way of D ratio of two to 2.5 it have to be flat it ought to be delicate and parallel lens have got to be there so there must not be any eccentric metropolis of the sample foil it is the loading is being carried out and their tolerance limits are already given in isolation specifications HTM requisites that have to be followed while that scan is being applied on this experiment which you can say that is the one video of the experiment in this test you will see the loading is being carried out come for a compressive test sample so this sample is positioned there’s no eccentricity the plates are parallel to one another even as it is below loading and regularly with a fixed loading fee the weight is being expanded on the sample 250 [Music] 16:17 improved complement to the Rockville 8090 300 [Music] and yep he goes proper there [Music] instantly the load is launched from the sample so this is the so this is the specimen which is subjected to a compressive load and the compressive strength can be assessed by making use of the system P is equal to strength is equal to P by F where P is the failure load failure load is the subject cross sectional area of the specimen so on this case the loading is given uniaxial ii the loading in different two instructions just isn’t to be had so the common loading is this one and specimen is subjected to load so that is the string may also be quite simply calculated using this this is the radial pressure and this is the axial stress and in the event you plot the curve between stress and strain you’re going to discover the failure is like this so there is a sudden failure of the material if it the material is brittle in this position so this is original traits of a compressive trying out tensile checking out is clearly carried out the place direct tensile checking out will not be perpetually feasible so in direct tensile checking out is carried out in Brazilian experiment pattern in Brazilian scan pattern where the specimen is placed specimen is placed like this and it’s loaded radially so what’s happened though the loading is given compressive however the specimen fails on that aircraft the place the forces are performing in a tensile path so because of this this strength parameter is truly observed is the – is the tensile strength no longer the compressive strength so Brazilian tensile scan is in actual fact an indirect tensile force dimension 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 by means of D ratio it is mistakes are there half of is taken L by using D ratio of half of is taken below compressive loading laptop and it’s platen sir diametrically positioned domestically throughout the specimen so that is the platen flattens are placed diametrically throughout the specimen and the burden highest load to fracture the specimen is recorded and the tensile strength is computed as Sigma T is the same as 2 P by 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 pattern and P is the so truly this is the p is the failure load this is the method to give us the tensile strength of the rock specimen so let us notice let us become aware of one such video to be had in the YouTube for the tensile force measurement of some concrete specimen so right here the beauty of this video is that in this video you can detect this in a slow % also it reminded in a slow space so that is the cylindrical pattern of all set with usual Portland cement and you’ll find the true-time video of 25 FPS of this failure so as the specimen is subjected to load you can find the tensile cracks are created across the diameter and the specimen fails underneath tension so this is the gradual % you can see the propagation of the cracks in the specimen propagation of the cracks within the pacing specimen you will discover the cracks are being widened steadily and in the end the specimen fells so that is the vertical load versus vertical displacement graph so this is the direct shear scan typically tensile failure could be very not often occur within the rock as a rule we provide the compressive load on to the rock and rock fills below compression however normally rock fails underneath tension also whilst we will be able to talk about concerning 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 when Rock fails under compression it disintegrated right into a quantity of pieces the place it fails under anxiety it disintegrates into only two pieces no longer a quantity of pieces so essentially tensile failure offers us a protracted crack even as compressive failure gives the in quantity of smaller fragmented fabric so this is the reason compressive failure the power is that it’s compressive load will also be readily given onto the fabric and it’s problematic to furnish the tensile load onto the fabric however compressive strength is highest for the rock tensile strength is the minimum of the rock so the tensile force of the rock is minimal then also it’s not almost always practiced on account that that offering a tensile load onto the material is tricky so hammering etcetera all these are the failure of fabric under compressive load not the tensile load so sincerely in between this two strength there is the shear strength the general values of stress shear strength of the rock is lesser than the compressive force but better than the tensile force rock fails below sea are additionally typically rock fails underneath shear most of the occasions on the grounds that of the shear in number of masses are acting on the rock in on in-situ situation and that’s making a shear loading on rock as mostly it’s happen due to the fact of the heterogeneity of the the direct shear is measured on the direct shear test equipment nevertheless direct shear scan apparatus is relevant for the loose material for the tender material most effective in view that in any other case it this are not able to be utilized so in direct shear experiment there is a this shear strength is determined the traits of rock alongside the airplane of weakness the specimen is placed within the scale back 1/2 of the shear field and encapsulated in either artificial synthetic resin or mortar the specimen need to be placed in order that the road of motion of the shear force lies within the plane of the discontinuity to be investigated and the natural force acts perpendicular to the to this surface so was once the encapsulated material encapsulated fabric has hardened the specimen is established within the upper half of of the shear field within the identical manner a strip approximately 5 mm huge above and below the sheer floor ought to be saved free of encapsulating material the scan is then applied by way of making use of a horizontal shear drive T beneath a consistent typical load so this is the fundamental requirement that it have to be applied in a typical traditional load now you will see that this video the place the direct shear is being carried out of a free fabric sand fabric so that is to check the shear strength that is the direct shear operators these are the loading pad perforated plates etcetera this is the owing laptop to make use of the way the material lose fabric so sandy soil material is taken of fixed variety then the shear field is set this is the shear box then first the keeping plate has to be supplied then the perforated plate or stable grid pair plate then the fabric will be placed on that then the fabric can be compacted in order that the above perforated plate replaced will probably be positioned on this then the higher plate shall be positioned on this now the loading plaid sample be placed on that then the ordinary load is which is under hanging shall be placed on this now the desired usual load is also suspended from this plate so these are the typical fixes for fixing the average load then the horizontal drive will be given from the you hydraulically operated motors and the failure load will probably be recorded so this is the direct shear experiment may also be applied on the pattern so let us stop at this position from this for this lecture we will continue to look the have an impact on of alternative homes within the subsequent type thank you

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