Bulldozers
Hello everyone, I welcome you all to the lecture 10 of this course construction methods and equipment management. In this lecture, we are going to discuss about the earthmoving equipments specifically about the bulldozers.(Refer Slide Time: 00:41)So, in the last lecture, I introduced you to the various fundamental terms related to earthmoving operations, like how to determine the power requirements of the machine and what is the significance of performance chart, how to quantify the payload of the machines? So, all those terminologies related to the earthmoving operations were introduced in the previous lecture.Now, let us see what is the outline of today's presentation? So, in the today's presentation, we are going to discuss about what are all the applications of the bulldozer. So, there will be some series of lectures on different earthmoving machines. So, in this lecture we are going to discuss about the bulldozer. We will look into what are all the uses of bulldozer and what are all the different types of the earthmoving blade which we use commonly for the bulldozer.So, what are all the possible blade adjustments and the blade movements with the bulldozer, how to assess the blade performance. Say and what are all the different productive dozing methods which can be adopted to enhance the productivity of the bulldozer. So, the factors which affects the productivity of bulldozer and how to estimate the productivity of the bulldozer with some in illustrations. So, these are the things which are going to discuss in the upcoming slides.(Refer Slide Time: 01:58)So, most of you might have seen the bulldozer, it is basically a tractor unit connected to your earthmoving blade. So, it is nothing but your tractor unit connected to your blade. So, with the help of this blade, you can push the material from one location to another location. So, you can see that there are possibilities of different types of the connection between this blade and the tractor. So, here you can see a type of connection tilt cylinder and a pusher arm arrangement, so with this you can adjust the blade movement. So, similarly there are also possibilities of different types of connections.(Refer Slide Time: 02:36)Like say for example, you can have a C frame connection like this, C frame connection between the tractor and the blade. So, with this particular kind of connection, certain types of movements of blade are possible. So, basically the connection between the tractor unit and the blade will decide what are the possible movements or the adjustments for the particular blade. So, we will discuss about the blade movements later.(Refer Slide Time: 02:58)So, this bulldozer is basically a versatile machine. So, it can be used for different types of applications in a construction project site. So, before you select an earthmoving equipment for your particular activity or your particular job, you should know what is the haul distance actuallyneeded for your actual job, because every earthmoving equipment has it is own economic haul distance.So, every equipment has it is own economic haul distance, this we have discussed earlier also. So, the economic haul distance of a bulldozer, the maximum distance is only 100 meter. So, beyond 100 meter it is not advisable to use this particular machine, you will not get you desired productivity and if you will use it will result in lot of wear and tear for the particular machine. So, this machine is designed only for a haul distance of up to 100 meter.So, the actual distance will design depending upon your size of your machine, your size of your dozer, and the type of the material which you are going to handle, which you are going to push which the bulldozer is going to push. Say if you are going for a bigger tractor, bigger bulldozer, the economic haul distance maybe slightly higher than this. So, the actual distance depends upon the size of the dozer, greater the dozer the economic haul distance will increase.Similarly it also depends upon the material which the bulldozer is going to push, say some material are cohesive some material are non cohesive. Say generally the bulldozer can push a cohesive material more easily when compared to non cohesive material like sand is non-cohesive material. Because a cohesive material can easily roll in front of the blade, so it is easy to push, but your sand it will remain like a dead material, it will not roll easily.So, the pushing of the sand is little bit difficult with the bulldozer. So, in the case your haul distances get reduced. What is a haul distance possible? Depends upon your size of a bulldozer and it also depends upon the type of the material which you are going to push with the bulldozer. So, commonly you can say the maximum haul distance is up to 100 meter. So, apart from the earthmoving operation, you can use this machine for so many activities.So, you might have seen bulldozer, used for cutting trees So, it can also be used for clearing the vegetation at the construction site. So, for opening up of roads through mountain, it is a very common supporting machine. So, very commonly it is used as a supporting equipment. Say forexample, for pushing or towing other machines this can be used. Say this scraper; scraper is another earthmoving machine which we are going to discuss in the upcoming lecture.So, this scraper will also cut the earth, there will be a bowl in the scraper, there will be a blade with the help of the blade you can cut the earth and fill the bowl in the scraper, so this is called as the loading operation. During this particular loading operation, I can take the help of a bulldozer to push the scraper, so that the job of the scraper will be easier. So, that this is used as a supporting machine.Similarly spreading so you can use the bulldozer for spreading the earth for preparation of your subgrade for your road or whatever for spreading the earth, for filling the trenches for backfilling the trenches, for maintaining the haul roads. So, different applications it is used, that is why we call it as a versatile machine.(Refer Slide Time: 06:36)So, let us see some examples. Now you can see this bulldozer can be used for land clearing, so it is used for cutting the trees clearing your site. So, these are special bulldozers, for this purpose, we should not use a earthmoving blade, there are special land clearing blades it is called as land clearing blade. One such land clearing blade is Rome K bar G clearing blade, it is a very powerful blade, manufactured by Rome company.So, this blade you can see it as a vertical knife called as stinger and the horizontal knife called as web. So, it has both the vertical knife and the horizontal knife, so with this, you can easily cut the trees. So, generally for cutting the trees, you need more tractive effort, more power is needed, so you have to use the very big bulldozer. So, you have to choose a very big tractor unit, so that you will be able to deliver more power.And one more important thing you need to note is there is cutting edge at the bottom of every blade. So, generally when you use the blade frequently, the one which gets worn out very fast is the cutting edge. So, we do not replace blades very often, we replace the cutting edge only. The cutting edge is just bolted; it is just bolted at the bottom of the blade. So, once it gets worn out, you can just replace it with a new cutting edge. So, generally we do not replace blades frequently, but we replace only the cutting edge at the bottom of the blade.(Refer Slide Time: 08:04)So, this is what I told you earlier, the bulldozer is used for assisting other machines, so it is supporting the other machines. So, this is your bulldozer, so this is a schematic sketch, so the leading one is your scraper. As I told you the scraper has to cut the earth and fill its bowl. So, during that loading operation, your bulldozer will push, you can see it has a special type of blade just for pushing it that blade is called as cushion blade.I will explain you later when we discuss about the type of blade. So, this bulldozer will push the scraper during the loading operation of the scraper. So, by that process you can enhance the productivity of your scraper. So, this is one application of the bulldozer.(Refer Slide Time: 09:08)So, other application you can see it can be used as a ripper. So, for this tractor you can see a front end you have this blade earthmoving blade, this is the earthmoving blade, so at the rear end, you have this ripper. So, this is similar to plough what we use in farming. So, basically when we discuss about the earthmoving operations, the steps involved in the moving operations, I told you like the first step is we should loosen the earth before digging it.So, when you loosen the earth before digging it, the digging becomes easier that will enhance the productivity of the digging job. So, that is my first say for example particularly for the hard terrain, if it is going to be a consolidated clay terrain. In that case first use the ripper, then loosens the earth with the help of the ripper. Once after you loosen it, then use the earthmoving blade and push the earth.So, we can follow the sequence, so that you can enhance the productivity of the job. Similarly even before using scraper, scraper is also earthmoving machine. Before using the scraper, I can use a bulldozer with a ripper attachment, loosen the earth first, then use a scraper for loading,thereby you can enhance the productivity of the scraper. So, this ripper is basically to loosen this material, you can also use this for ripping the rocks, so this can also be used for ripping rocks.So, you know that the commonly adopted method for excavating the rock is drilling and blasting method, so that is actually always a costlier method. So, if you are able to use ripper for ripping the rock, you can have a huge saving in the cost. So, first before that you have to check the rippability check the rippability of your rock for that there are some special methods like seismographic methods, we are not going to discuss that in this particular lecture.There are some seismographic techniques, sound seismographic techniques based upon that you can check whether the rock rippable or not. Once you know that the rock is rippable, you can use this technique for ripping it that will result in huge saving in the cost. Similarly you can use it also for ripping a old pavements. So, it can have different applications accordingly.(Refer Slide Time: 11:19)Then stripping, stripping is a very common operation in the construction project site. So, you know that stripping is nothing but removal of the top layer of the soil. So, if the top layer of the soil is weaker one with lot of vegetation, so you have to remove the top layer of the soil. So, depending upon a depth to which the vegetation is available in your soil accordingly you have to remove the top layer, so that is what is stripping.So, bulldozer you can see very commonly used for stripping the top layer. So, as I told you, the bulldozer is economical only for the haul distance of 100 meters. The actual distance depends upon your size of a dozer and also the material which you are pushing. So, if you are pushing a cohesive material, it is easier for a bulldozer to push, so you can have a little bit greater the haul distance.But if you are going to push the sand which is non cohesive, in that case your haul distance is still going to be reduced. It depends upon the type of materials which you are going to encounter in your project site.Let us workout the solution for this problem. As I told you the first step is we need to find the uncorrected maximum production for the 60 meter push distance for the standard soil density of 1365 kg per meter cube. So, how will you find the production? So, using the production curves as I told you using this production curve for your model and for the dozing distance, what is the value we can take it, this is called as the uncorrected value.So, this uncorrected value according to your project conditions, you need to correct it. So, first I am going to choose this value from the curve supplied by the manufacturer. So, that value is found to be 114.68 loose meter cube per hour, this value I am going to adjust according to my project conditions. So, next is and you should note that this is valid for the soil density of 1365 kg per loose meter cube, but in your project the soil density is different.So, it is given 1750 kg per meter cubic bank state, so you have to adjust it accordingly. Now the next is visibility correction factor. So, in this problem it is given foggy condition by the ideal curve is for the excellent visibility. So, you have to apply the correction factor it is found from the manufacturer is 0.8, so I have given you the value directly. Operator correction, here the operator skill is average and for the track mounted machine, the correction factor is going to be 0.75, if the operator skill is excellent, you need not apply correction factor.Then slot dozing, in this problem you have adopted slot dozing. So, from dozing method perspective, this is even better than the ideal curve value. So, here you can see correction factor is 1.2 because this is going to enhance your productivity greater than 1.(Refer Slide Time: 1:27:50)Grade correction, you are moving down the slope -15%. So, your correction factor increases, it is going to enhance the productivity. So, from grade perspective, it is better than the value taken from the ideal curve. Then material type, here it is non cohesive silty sand, so obviously it will affect the productivity correction factor is less than 1, 0.8. Job efficiency, machine is working for 50 minutes in a hour, so accordingly 50 by 60, find the correction factor it is 0.83.But ideal curve was based on 60 minutes in a hour. So, job efficiency was 1 for the ideal curve, you have to apply according to your project condition, you have to correct it according to your project condition. Then machine transmission factor, so in this problem also it is automatic gear change, power shift mode, so you need not apply any correction factor, so it is just 1, it is same as the ideal condition. In a ideal condition also it is power shift mode, here also it is power shift mode.(Refer Slide Time: 1:28:58)Now another important correction factor which we are yet to determine is material weight correction factor. As I told you in this project we are going to deal with non cohesive silty sand. It is unit weight is given as 1750 kg per meter cube in bank state; it is 1750 kg per meter cube in bank state, so this is your actual project. But the curve value what we have chosen, productivity value what we chosen is for the ideal condition where the soil density is 1365 kg per meter cube.So, it is in loosen state, loose meter cube, so it is in loosen state. So, I need to compare both, so that we can apply the correction factor. So, we can compare both only when the volume is the same type of measure, but one volume is in bank state other volume is expressed in loosen state So, let me convert this bank state into loosen state, so that I can compare it. So, how to convert the bank density into loosen density?I can make use of the swell percentage value given, so you can see when the conversion. Swell percentage is nothing but bank dry unit rate divided by loose dry unit weight -1 into 100, that gives as swell percent. So, from the bank state, how much it has expanded to loosen state? That is what is swell percent. So, when you excavate the soil from the natural state when it gets loosened how much it swells or expands that is what is swell present.So, that is what it is given as 14%. Now, let us convert the bank dry unit rate into loose dry unit rate. So, you know bank dry unit weight and you know the swell percent what is unknown isloose dry unit weight. Swell percent is 14 equal to bank dry unit weight is 1750 kg per meter cube divided by loose dry unit weight -1 into 100. So, you can move this to left hand side. So, 14 by 100 + 1 is nothing but 1.14 = 1750 divided by loses unit weight.Now your loose unit weight is nothing but 1750 divided by 1.14 that is nothing but 1,535.09 kg per loose meter cube. So, this is what is determined here, loose unit weight is nothing but 1750 that is bank unit weight divided by the 1.14 that gives you 1535.09. So, we have converted the bank unit rate into loose unit weight.(Refer Slide Time: 1:32:07)So, now you can compare both, your standard condition is 1365 kg per loose meter cube. So, now your project condition is 1,535.09, per loose meter cube. So, obviously your project soil is more denser than compared to the standard condition curve. So, that means, this is going to affect your productivity when the soil is more denser, it is going to be difficult for the bulldozer to push it. So, that is definitely going to reduce the productivity.So, you will not be able to realize your productivity as represented by the ideal curve. So, you have to adjust it according to the material weight correction factor. So, how to find the material weight correction factor? It is nothing but 1365 divided by 1,535.09. So, that gives me the material correction factor as 0.8. Obviously it is also less than 1; it is going to reduce my productivity. So, this is your material weight correction factor.(Refer Slide Time: 1:33:12)Now let us find the product of all the correction factors. So, whatever correction factors we have discussed so far, let me summarize. So, one is your visibility correction factor 0.8, operator skill correction factor 0.75, correction factor for slot dozing 1.2, grade 1.3, material type 0.8, material type connection is different from material weight. Job efficiency 0.83, machine transmission, here we need not because both the cases it is only power shift factor.So, it is just 1 and material weight correction factor is 0.89, so these are all the correction factors. You find the product of all the correction factors you will get the answer as 0.553. So, this is the value you have taken from the ideal curve, hope you remember from the ideal curve, so from the actual medical supplied by the manufacturer. So, I have taken the value as 114.68 loose meter cube per hour.So, this 114.68 loose meter cube per hour, I am adjusting according to my project conditions by applying these correction factors. That gives the corrected productivity value as 63.42 loose meter cube per hour. So, hope you understand. So, for the ideal condition the productivity is very high but when you adjust it according to your project condition, you can see that the productivity got reduce significantly 63.42 loose meter per hour.(Refer Slide Time: 1:34:51)Now the next part, after estimating the productivity, now we are supposed to estimate the unit cost of production, unit cost stop earthmoving operation. So, how to do that, and they asked you to calculate unit cost per bank meter cube. So, that is what is asked in the problem cost per bank meter cube we have to calculate that. So, we need bank meter cube, but what we have calculated so far is your loosened volume.So, what you know is the information in the loosen state. So, now we have to convert this loosen state value I mean loosen measure again into the bank measure. So, then only we can estimate the cost per bank meter cube. So, the same swell percentage formula you can use for the conversion. So, your swell percentage is nothing but bank unit weight by loosened unit weight - 1 into 100, so the swell percent is 14 for the soil.And one more thing is, so here it is in volume loose meter cube but the formula is in unit weight, density. So, it is nothing but weight by volume, weight by bank volume. So, weight is going to be same for both the cases only the volume volumetric measure is different weight by loosen volume. So, weight is going to be same can cancel it -1 into 100. So, if we move this to the left hand side 14 divided by 100 + 1, so that is nothing but 1.14 equal to lose volume divided by bank volume.So, now you can calculate, so I need to calculate now bank volume. So, bank volume is nothing, but production in bank state is nothing but the loosen productivity divided by 1.1 that is it. So, you need to calculate bank state, so it is nothing but bring it this. So, it is nothing but bank state productivity is nothing but loosen productivity divided be 1.14. So, that gives you 55.63 the bank meter cube per hour. So, now you know the hourly productivity in bank state your estimated, so you need to know the hourly cost. So, how to calculate the cost?(Refer Slide Time: 1:37:32)Already it is given to you the ownership and the operating cost is 1100 per hour, operator cost is given. So, cost per hour = 1100 + 350 rupees, so that gives you 1450 rupees per hour is the hourly cost. So, now let me calculate the cost per bank meter cube, it is nothing but the hourly cost by hourly productivity. So, 1450 divided by hourly productivity is 55.63, so this gives me the answer as rupees 26.06 per bank meter cube.So, this is how you calculate the unit production cost. So, this is a very important parameters as I told you when you plan for your bidding. So, when you plan for your bidding when you go from unit rate contract, so in the unit rate price what you quote this part will also over a component of that. So, that is why you have to be very careful in the estimation of the unit production cost.For that you need to have a thorough knowledge on how to estimate the cost associated with the machine and the productivity associated with the machine, then only you can make an accurate estimate of the unit cost of production.(Refer Slide Time: 1:38:51)Now let us workout another problem a different approach of estimation of the productivity. So, in this a crawler type bulldozer is given, this equipped with power shift mode. So, automatic gear change, it pushes a loose soil with blade capacity 6.5 loose cubic meter. So, the blade capacity is given to you 6.5 loose cubic meter, and the dozer pushes the loose soil over a distance of 45 meters.So, the dozing distance is given as 45 meter and the speed of the machine is given 4 kilometer per hour, dozing speed is given as 4 km per hour and maximum reverse speed in the third range is 8 kilometer per hour. So, mostly since a bulldozer is operated for short distances, so the return journey it will be mostly operated in the reverse gear. So, the return speed has given as 8 kilometer per hour.Obviously the return speed will be greater than the dozing speed because the blade is unloaded or empty, so it has to be greater. Now estimate production of the bulldozer in loose cubic meter, if the job efficiency is 50 minute per hour. So, since it is a power shift mode, you can assume the fixed cycle time for the power shift dozer as 0.5 minute. So, the maneuver time when you go forautomatic gear change machines is 0.05 minute, you can assume that. So, that will be your fixed cycle time, this is your fixed cycle time. So, now, we are going to estimate the productivity of the bulldozer, so with the available input data. So, how to estimate it?(Refer Slide Time: 1:40:39)So, you know the blade capacity, you know the blade load, that is known. So, you know the haul distance the dozing distance is known, so it is known, you know the speed of the machine. If the speed is not given in that case you have to go for the performance chart, with the help of performance chart you have to find the speed. But in this problem speed is given to you directly.(Refer Slide Time: 1:41:05)So, you know the haul distance and speed, so you can calculate the cycle time. So, based on using this input parameters, I can estimate the productivity of the bulldozer. So, let us see how it is done.(Refer Slide Time: 1:41:18)So, first the total cycle time is nothing but fixed cycle time plus variable cycle time. So, the time needed for cutting and pushing the earth and the returning back. So, the return time plus the maneuver time, your maneuver time is nothing but fixed cycle time, maneuver is nothing but time for changing the gears, increasing the speed or decreasing the speed. So, those things come into the maneuver time, for this power shift mode it can be taken as 0.05 minute. So, now we have to estimate the variable cycle time. So, that depends upon your haul distance and the speed.(Refer Slide Time: 1:41:53)So, variable cycle time is nothing but it is made up of dozing time and the return time, onward journey, return journey. So, dozing time you know the dozing distance 45 meter and the speed is given 4 kilometer per hour. So, let me convert, so let me find the dozing time, so the distance is given as 45 meter and the speed is given as 4 kilometer per hour. So, let me convert this kilometer per hour into meter per minute, the conversion factor is 16.67, 1 kilometer per hour is 16.67 meter per minute.So, multiplied by 16.67, so I will get the answer in minute, so it is nothing but 0.67 minute you can simplify you will get it. Similarly the return time, so return time is the same distance 45 meter but the speed is different, speed is higher here it is 8 kilometer per hour. So, convert it into meter per minute 16.67. So, that gives you the answer as 0.34 minute, so you return time is 0.34 minute, dozing time is 0.67 minute. So, now your total cycle time is supposed to calculate.(Refer Slide Time: 1:43:13)Total cycle time is nothing but your maneuver time, maneuver time is your fixed cycle time 0.5 and the dozing time 0.67, return time is 0.34, add everything you will get 1.06 minute, that is your cycle time. Now you calculate the productivity, I need a productivity and loose meter cube per hour, so how to calculate that? I know the blade load, so the blade load was given to you as 6.5 loose cubic meter.So, use this value 6.5 loose cubic meter divided by the total cycle time is 1.06 minute. So, I need the answer in loose meter cube per hour. So, let me convert this minute into hour, divided by 60, 1.06 divided by 60. And one more important thing you have to multiply it by the job efficiency. So, you are going to work for how much time in a hour that is job efficiency, working efficiency 6.5 divided by let me simplify 6.5 into 60 divided by 1.06.So, what is the job efficiency? It is nothing but it works for 50 minutes in a hour, it is given in the question like the job efficiency is 50 minutes per hour, so it is 50 by 60. So, you can get the answer as 306.60 loose meter cube per hour, so this is your final productivity. So, this is one way of estimation, so depending upon the input data accordingly you can choose the approach.(Refer Slide Time: 1:44:52)So, now we have come to the end of the lecture on bulldozer. So, let me summarize what we have discussed so far. So, as you know that bulldozers are versatile machines, so because it is used for different applications. So, not only for the earthmoving operations, we can also use it for cutting the trees, ripping the rocks and for assisting other machines. So, it is used for n number of applications, so that is why we called as a versatile machine.So, and we saw that depending upon the type of connection between the blade and the tractor, we can have different types of blade movements pitching, tilting and angling. So, if you have a C frame, then angling is possible, angling and tilting is possible. So, if you have tilt cylinder and pusher arm arrangement, in that case only pitching and tilting were possible, angling would not be possible.So, according to the type of connections, the blade movements will vary. And you can assess the performance of the blade using the parameters like cutting ratio and load ratio. And we discuss that with the dimension of the blade is smaller the cutting ratio and load ratio will be higher. So, for the straight plate as it is smaller, it is higher the cutting ratio and load ratio is higher when compared to the U blade.And other important thing is we have also seen what are all the different productive dozing methods which are adopted to reduces it is spillage, end spillage, slot dozing and blade to bladedozing. This can help you to increase the productivity of the earthmoving operation. And we have discussed about what are all the factors which affect bulldozer productivity, like the type of the plate, material type and cycle time. And we have worked out illustrations of how to estimate the productivity of the bulldozer using different approaches based upon the input data available.(Refer Slide Time: 1:46:42)So, these are the references which I have used for the preparation of this lecture. You can go through some of these textbooks to get more information related to this topic. In the next lecture, we will be discussing about the scrapers. So, scraper is also another earthmoving machine. So, we will be discussing about the different types of scrapers, applications and illustrations and how to estimate the productivity of the scrapers, thank you.
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