Purpose Of Compaction: Types Of Compaction

Purpose Of Compaction: Types Of Compaction Soil compaction is one of the most critical components in the construction of highway embankments, earth dams, foundations and many other engineering structure. Soil must be compacted to their unit weights, increase the strength characteristic which increase the bearing capacity of foundations constructed over them. Soil is compacted by removing air and water from its pore space. Compaction is a change in soil structure, not just an increase in soil density. Healthy soils have a diversity of pore sizes, while compacted soils have mostly small pores. In general, Soil compaction is defined as the method of mechanically increasing the density of soil. In construction, this is a significant part of the building process. Almost all types of building sites and construction projects utilize mechanical compaction techniques. During the compaction process soil partials are pushed closer together. This reduces the size of pores, the continuity of pores, and the size and stability of aggregates. Only under severe compaction will aggregates break down.This soil density chart shows properly compacted soil. Purpose of soil Compaction: The principal reason for compacting soil is to reduce subsequent settlement under working loads. Also in a construction material, the significant engineering properties of soil are its shear strength, its compressibility, and its permeability. Compaction of the soil generally increases its shear strength, decreases its compressibility, and decreases its permeability. in addition, compaction reduces the voids ratio making it more difficult for water to flow through soil. This is important if the soil is being used to retain water such as would be required for an earth dams. So we conclude that there are four reasons to compact the soil: Increase load-bearing capacity. Prevent soil settlement. Provides stability . Reduce water seepage, swilling and construction. Poor compaction can lead to unwanted results. Figure: result of poor compaction Types of compaction: There are four types of compaction that are commonly used on soil and/or asphalt: Vibration Impact Kneading Pressure Each of these types is carried out using one of two types of forces: static or vibratory. Static force relies on the weight of a machine to apply downward pressure on soil, thus compressing the soil particles. Adding weights to, or removing them from, the compaction machine can adjust the amount of pressure. Although effective, static compaction is best suited for the upper soil layers. The types of compaction that fall under static are kneading and pressure.Padfeet on a Caterpillar CP563 Vibratory force, on the other hand, uses mechanically driven force to apply downward pressure in addition to the weight of a machine. The mechanically driven force is an applied vibratory force that rotates the eccentric weight of a piston and spring combination. Compactors achieve compaction through the use of delivering rapid blows, or impacts, to the surface. This is effective in that it not only compacts the top layers, but the deeper layers as well. With vibration, the particles are set in motion and moved closer together to form a high density Compaction soil types: Different types of compaction are best suited for different soil types and conditions. This is because of the underlying density and moisture that different soil types are able to retain. Soil types are classified in three soil groups, with consideration to grain sizes. These types are: Cohesive Granular Cohesive and granular Cohesive In cohesive soils, such as clay, the particles contain characteristics that make them easily stick together so compaction can be achieved by high impact, which forces the air out of the particles, pushing them together. Granular Granular soils include sand, gravel, and other particles that typically range in size from 0.003 to 0.08 inches (0.008 to 0.2 cm). Because granular soils have good water-draining properties, they are able to obtain high density when fully dry or saturated. Granular is best compacted by shaking or vibrating the particles. Any type of vibratory equipment is best suited for this type. Depending on the type of granular soil, different degrees of vibration are required. Granular and Cohesive Often, soils are a mixture of both granular and cohesive, requiring more precise compaction equipment. Equipment should be chosen on the basis of the soil in the mix that is present in the highest percentage. Some materials, such as asphalt, require both vibration and static pressure to be compacted effectively. Machinery uses frequency and amplitude to apply a force for compaction. Frequency is the measure of the speed of the eccentric shaft rotation, or of the jumping of the machine, quantifiable by vibrations per minute (vpm). Amplitude measures the maximum movement of a vibrating body from its axis in one direction Field Tests: It is important to know and control the soil density during compaction. Following are common field tests to determine on the spot if compaction densities are being reached. Sand Cone Test (ASTM D1556-90): A small hole (6 x 6 deep) is dug in the compacted material to be tested. The soil is removed and weighed, then dried and weighed again to determine its moisture content. A soils moisture is figured as a percentage. The specific volume of the hole is determined by filling it with calibrated dry sand from a jar and cone device. The dry weight of the soil removed is divided by the volume of sand needed to fill the hole. This gives us the density of the compacted soil in lbs per cubic foot. This density is compared to the maximum Proctor density obtained earlier, which gives us the relative density of the soil that was just compacted. Nuclear Density (ASTM D2292-91): Nuclear Density meters are a quick and fairly accurate way of determining density and moisture content. The meter uses a radioactive isotope source (Cesium 137) at the soil surface (backscatter) or from a probe placed into the soil (direct transmission). The isotope source gives off photons (usually Gamma rays) which radiate back to the maters detectors on the bottom of the unit. Dense soil absorbs more radiation than loose soil and the readings reflect overall density. Water content (ASTM D3017) can also be read, all within a few minutes. A relative Proctor density with the compaction results from the test. How the Nuclear Density test works How the Sand Cone test works FACTORS AFFECTING COMPACTION IN THE FIELD: Compaction of a particular soil is affected by following given factors: MOISTURE CONTENT Proper control of moisture content in soil is necessary for achieving desired density. Maximum density with minimum compacting effort can be achieved by compaction of soil near its OMC (Optimum Moisture Content). If natural moisture content of the soil is less than OMC, calculated amount of water should be added to soil with sprinkler attached to water tanker and mixed with soil by motor grader for uniform moisture content. When soil is too wet, it is required to be dried by aeration to reach up to OMC. Moisture content of the soil is vital to proper compaction SOIL TYPE Type of soil has a great influence on its compaction characteristics. Normally, heavy clays, clays and silt offer higher resistance to compaction where as sandy soils and coarse grained or gravelly soils are amenable for easy compaction. The coarse-grained soils yield higher densities in comparison to clays. A well-graded soil can be compacted to higher density. LAYER THICKNESS The more the thickness of layer of earth subjected to field compaction, the less the energy input per unit weight of soil and hence, less is the compaction under each pass of the roller. Suitable thickness of soil of each layer is necessary to achieve uniform thickness. Layer thickness depends upon type of soil involved and type of roller, its weight and contact pressure of its drums. Normally, 200-300 mm layer thickness is optimum in the field for achieving homogeneous compaction. CONTACT PRESSURE Contact pressure depends on the weight of the roller wheel and the contact area. In case of pneumatic roller, the tyre inflation pressure also determines the contact pressure in addition to wheel load. A higher contact pressure increases the dry density and lowers the optimum moisture content SPEED OF ROLLING Speed of rolling has a very important bearing on the roller output. The greater the speed of rolling, the more the length of embankment that can be compacted in one day. Speed was found to be a significant factor for vibratory rollers because its number of vibrations per minute is not related to its forward speed. Therefore, the slower the speed of travel, the more vibrations at a given point and lesser number of pass required to attain a given density. TYPE OF COMPACTING EQUIPMENTS A large variety of mechanical equipments is available for compaction of soil but soil type and moisture condition will often dictate the type of equipments and method of use. Some important compacting equipment are given below: 1. Light compacting equipments (Rammers/Plate compactors) 2. Smooth wheel rollers 3. Sheepsfoot rollers 4. Pneumatic tyred rollers 5. Vibratory rollers 6. Grid rollers 2003 Dynapac CC122 Tandem Vibratory Smooth Drum Roller . Figure: Smooth wheel-Roller http://www.rentittoday.com/cmsAdmin/uploads/thumb/Rammer-or-Upright-Tamper_002_001_001_001_001.jpg figure: Light compacting equipments (Rammers) Summary: Soil compaction is an important part of the construction process. It is used for support of structural entities such as building foundations, roadways, walkways, and earth retaining structures to name a few. In general, the preselected soil should have adequate strength, be relatively incompressible so that future settlement is not significant, be stable against volume change as water content or other factors vary, be durable and safe against deterioration, and possess prop Refrances: Das, Braja M. (2002). Principles of Geotechnical Engineering.fourth edition. P100 IS: 2720-1983 (Part-14)- Determination of density index (Relative Density) of cohesion New Used Heavy Equipment http://www.ritchiewiki.com/wiki/index.php/soil_compaction#ixzz2CglEjAcM Engineering Properties of Soils Based on Laboratory Testing Prof. Krishna Reddy, UIC Das, Braja M. (2002). Principles of Geotechnical Engineering.fourth edition. P100

Gender roles Essay

Well, the topic of gender roles is a ripe one. While there is no specific outline providing benchmarks to use in classifying a person’s gender, a number of factors come into play in helping define one’s gender. One of the factors is cultural prescription as provided for by a person’s social group. A man is a man or a woman a woman depending on how the social group they belong to label or socializes them. But one should remember here that genitalia alone do not determine a person’s gender. While one’s sex is determined by one’s biology, both biology and culture (nature and nurture) determine their gender. There are different roles for different genders. Gender is more of culturally than biologically determined. In fact, a person could be born with male genitalia but be of female gender or vice versa. Differences exist between the male and female genders for instance; men are braver than women and women more emotional than men. Women like being protected while men like to protect. Also, men want to pursue a woman for relationship while women want to be pursued. The differences between the genders emanate from differences in sexes culture, religion among others. Some of the similarities include: both are jealous, self-centered and want to mend the other to live up to their own standards. Again, both genders converge in their need for recognition and love. These among other differences and similarities together with other factors such as legal have succeeded in being constant obstacles on the road to equality. Most social groups, our parents and the media have socialized us to believe that the male gender is superior to the female gender. One can ask, does sex determine one’s abilities? Pursuing such a question may elicit an endless debate but a sex-based approach in determining gender roles is bias and oppressive to women and perpetuates inequalities and patriarchy. No wonder women have to fight for equality. Kyra Sedgwick says that, â€Å"†¦we are still not really supposed to want it as much as guy does. † But I think women should be able to make their own choices. I would want to socialize my children in a manner that they will see both genders as equal and worth as much respect despite the differences. I will also want to allow them freedom to choose what they want to be in life. I will not deny them opportunities on the basis of their gender. I will also encourage them to follow their passion provided they are within the range of acceptable careers and I will endeavor to support them. A number of questions puzzle me. They include; In agitating for equality, do women become more women or less? Is a woman more woman because she enjoys same rights as a man? Is it possible to invent a universally acceptable modality of determining gender roles so as to eschew the controversy? What provisions do our societies make for those individuals who do not qualify as average male/female? These questions leave me lost in the labyrinths. The first and second questions demand that women be careful when agitating for equality lest they lose their identity. Anyway what is so serious about losing one’s identity? If forgoing one’s identity will make one have a happier life then isn’t it better to forgo it. What should be pursued, identity or happiness? Addressing the third question will save us unnecessary debates while the fourth question rises out of my worry that there are some persons that are left out in the classification of genders and this could be unfair- a more inclusive definition needs to be adopted for a fair discussion. In doing away with the dual classification such terms as feminism and others that are so ‘poisoned’ will be avoided and may be a less controversial nomenclature adopted. Andrea Wong is a brave woman. From her early age she tried her leg in leadership, a field that was erroneously perceived as a reserve for men. Also unlike most women, Andrea Wong knows how, after falling, to get up, dust herself off and keep going. Unlike Wong, most women get resigned after their first failure. If women were like her, they would also be leaders like she is today and would be doing great exploits. Rachel Roy is another woman who impresses me. She goes for what she wants and she wants nothing but the best, â€Å" If I couldn’t work at Contempo, I didn’t want to work anywhere. † This shows a resolve that most women lack. She knows what she wants that is to be a designer, â€Å"her passion started in childhood and she has never wavered†. She is final in her decision. These two women not only set good example for me but also are good role models for women. From the pieces, it is clearly depicted that success for women is dependent on their attitude and not their gender. If women changed their attitude then they would favorably compete against men and it would be easier for them and tougher for men. Works cited Newsweek, October 15, 2007.

Bent Toward Your Goal, the Whole World Will Make Way Essay

Now I am in Grade 10 and I think about the life I have spent. I come to a conclusion: everyone’s life starts similarly, but the result is different. This is because some people do not know their own goals and only do what others do. Only people who know their goals can have a meaningful life. There are many ways in my life. If I am not careful enough, I will choose the wrong way. For instance, although some people look quite busy, what they do is not meaningful because they do not know their goal! It is necessary for you to know your goal and hold on to it unless you do not want to be successful. Ants use the whole autumn to save food in order to have a good winter. Farmers work under the burning sun in order to have a good harvest. They all know their goal and hold on to it. So do I. When I was in Grade 7, I knew there would be a basketball game in Grade 8. As a student who was crazy about basketball, it was a good chance for me to help my team, so I was sure of my goal. From then on, I began to learn from others and practiced again and again. Nothing could get in my way because of my determination. Although the sun was burning, the weather was hot, I never gave up because I believed: â€Å"no pain, no gain†. Finally, our team did a good job, and it was the result that I wanted. Begin with the end in mind makes me have a definite goal, and makes me go straight towards my dream. Consequently, I advocate that everyone should begin every day with a clear direction and destination and hold on to it. This can lead you to success!

What Is Object Permanence

Object permanence is the knowledge that an object continues to exist even when it can no longer be seen, heard, or perceived in any other way. First proposed and studied by renowned Swiss development psychologist Jean Piaget in the mid-1900s, object permanence is considered a key developmental milestone in the first two years of a child’s life. Key Takeaways: Object Permanence Object permanence is the ability to understand that an object still exists even when it can no longer be perceived in any way.The concept of object permanence was studied by Swiss psychologist Jean Piaget, who proposed a series of six stages specifying when and how object permanence develops during the first two years of life.According to Piaget, children first begin to develop an idea of object permanence at around 8 months old, but other studies suggest the ability starts at a younger age. Origins Piaget developed a stage theory of childhood development, which consisted of four stages. The first stage, called the sensorimotor stage, takes place from birth to approximately 2 years old and is when babies develop object permanence. The sensorimotor stage consists of six substages. At each of the substages, a new achievement in object permanence is expected. To detail the substages in the development of object permanence, Piaget conducted simple studies with his own children. In these studies, Piaget hid a toy under a blanket while  the infant watched. If the child searched for the hidden toy, it was seen as an indication of object permanence. Piaget observed that in general children were around 8 months old when they started to search for the toy. Stages of Object Permanence Piaget’s six substages in the achievement of object permanence during the sensorimotor stage are as follows: Stage 1: Birth to 1 Month Right after birth, infants have no concept of anything outside themselves. At this earliest substage, they experience the world through their reflexes, the reflex of sucking in particular. Stage 2: 1 to 4 Months Starting at around 1 month old, children start to learn through what Piaget called â€Å"circular reactions.† Circular reactions happen when an infant chances on a new behavior, like thumb-sucking, and then attempts to repeat it. These circular reactions involve what Piaget referred to as schemas or schemes — patterns of action that help infants understand the world around them. Infants learn to use multiple different schemes in circular reactions. For example, when a child sucks their thumb, they are coordinating the action of sucking with their mouth with their hand movements. During Stage 2, infants still have no sense of object permanence. If they can no longer see an object or individual, they may look for a moment to where they last saw it, but they won’t attempt to find it. At this point in development, the saying out of sight, out of mind applies. Stage 3: 4 to 8 Months At around 4 months, babies start to observe and interact more with their surrounding environment. This helps them learn about the permanence of things outside themselves. At this stage, if something leaves their line of sight, they will look where the object fell. Also, if they put an object down and turn away, they can find the object again. Further, if a blanket covers part of a toy, they can find the toy.   Stage 4: 8 to 12 Months During Stage 4, true object permanence starts to emerge. At around 8 months old, children can successfully find toys completely hidden under blankets. Yet, Piaget found a limitation to babies’ new sense of object permanence at this stage. Specifically, although an infant could find a toy when it was hidden at point A, when the same toy was hidden at point B, infants would again look for the toy at point A. According to Piaget, infants at Stage 4 are unable to follow displacements to different hiding places. Stage 5: 12 to 18 Months At Stage 5, infants learn to follow the displacement of an object as long as the infant can observe the movement of the object from one hiding place to another.   Stage 6: 18 to 24 Months Finally, at Stage 6, infants can follow displacements even if they don’t observe how a toy moves from hidden point A to hidden point B. For example, if a ball rolls under a sofa, the child can infer the trajectory of the ball, enabling them to look for the ball at the end of the trajectory instead of the beginning where the ball disappeared. Piaget suggested that it’s at this stage that representational thought emerges, which results in the ability to imagine objects in one’s mind. The ability to form mental representations of things they can’t see results in infants’ development of object permanence, as well as an understanding of themselves as separate and independent individuals in the world. Challenges and Critiques Since Piaget introduced his theory on the development of object permanence, other scholars have provided evidence that this ability actually develops earlier than Piaget believed. Psychologists speculate that Piaget’s reliance on infants’ reaching for a toy led him to underestimate the child’s knowledge of individual objects, because it overemphasizes infants underdeveloped motor skills. In studies that observe what children look at, instead of what they reach for, infants appear to demonstrate an understanding of object permanence at younger ages.   For example, across two experiments, psychologist Renà ©e Baillargeon showed infants screens that rotated towards objects in back of them. As they rotated, the screens concealed the objects, but babies still expressed surprise when the screens didnt stop moving when they expected them to because the object should have forced the screens to stop. The results showed that infants as young as 7 months old can understand the properties of hidden objects, challenging Piaget’s ideas about when object permanence first starts developing in earnest. Object Permanence in Non-Human Animals Object permanence is an important development for humans, but we’re not the only ones who develop the ability to understand this concept. Research has shown that higher mammals, including apes, wolves, cats, and dogs, as well as some species of birds, develop object permanence.   For instance, in one study, researchers tested cats and dogs’ object permanence with tasks that were similar to those used to test the ability in infants. When the reward was only a hidden toy, neither species managed to complete all the tasks, but they were successful when the tasks were adjusted to make the reward hidden food. These findings indicate that cats and dogs have completely developed object permanence. Sources Baillargeon, Renà ©e. â€Å"Young Infants’ Reasoning About the Physical and Spatial Properties of a Hidden Object.† Cognitive Development, vol. 2, no. 3, 1987, pp. 179-200. http://dx.doi.org/10.1016/S0885-2014(87)90043-8Crain, William. Theories of Development: Concepts and Applications. 5th ed., Pearson Prentice Hall. 2005.Dorà ©, Francois Y., and Claude Dumas. â€Å"Psychology of Animal Cognition: Piagetian Studies.† Psychological Bulletin, vol. 102, no. 2, 1087, pp. 219-233. http://dx.doi.org/10.1037/0033-2909.102.2.219Fournier, Gillian. â€Å"Object Permanence.† Psych Central, 2018. https://psychcentral.com/encyclopedia/object-permanence/McLeod, Saul. â€Å"The Sensorimotor Stage of Cognitive Development.† Simply Psychology, 2018. https://www.simplypsychology.org/sensorimotor.htmlTriana, Estrella, and Robert Pasnak. â€Å"Object Permanence in Cats and Dogs.† Animal Learning Behavior, vol. 9, no. 11, 1981, pp. 135-139.