CHAPTER 1
Introduction
Background
Soil is the common material that being used as base or foundation for every construction and it is needed to be compact first. This is because the soil that use contains high air voids. Air voids occur when there is air trapped between soil particles. High air void content in soil will decrease the soil strength and the soil is categorising as the loose soil. To remove air voids, mechanical energy is required and indirectly it will also cause changes in the water content. Compaction is where the process of turning the soil more dense. It is where the soil particles are press together to a closer state while expelling the air from the soil in process. Compaction will improve the engineering properties of soil. This is because the soil that compress will have a higher strength due to the position of the particles more closely. In addition, compressibility and permeability of the soil will become lower.
Figure 1:
The soil characteristic such as the density and the unit weight will be increase due to the expulsion of the air during the compaction process. The density and unit weight terms are often used mistakenly. The density is referring to the amount of mass per unit of volume ( kg⁄m^3 ) and the symbol of density is ρ. While on the other hand, the unit weight is referring to the weight per unit of volume (kN⁄m^3 ) and the symbol for unit weight is γ.
Figure 2:
Every soil has different characteristic with respect to the maximum density and optimum moisture. Soil types are commonly determined by grain size. Hence, it can be classified by conducting the sieve analysis test to determine the particle size of soil passing through the series of sieve to screen or separate different size of grain...
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...s compressed multiple times on each layer during the construction process, but the probability of sand to settle is still exists as so often happens the soil deposition in the abutment and Embankment. This probably is due to vibrations and loads applied to the soil repeatedly from its surroundings.
Therefore, the compaction test will be done in the laboratory by applying the same concept which is the sand in the mould will be compact and vibrate by using the variable methods of soil compaction so that the soil will experience the same situation as in construction work. The result among of these tests will be compare.
The study is to determine which of the soil compaction method is most effective way in terms of which method can compact the soil particles closer by referring to the difference of the sand volume in the mould before and after the compaction test done.
The most economical method for ground improvement is aggregate piers. Before aggregate piers were used, engineers had to replace the weak soil with an engineering fill in order to use shallow foundations, but in some cases (load is very high) they had to use deep foundations, which is much more expensive. By using aggregate piers, we can now use shallow foundations in marginal soil without having to replace it. By using compacted aggregate to create stiff pier element, aggregate piers help to increase the bearing capacity, liquefaction resistance, shear strength, rate of consolidation and it reduces settlement.
This chapter discusses the result of experiment of soil properties at the Orthosiphon Stamineus plot, INSAT as describe in chapter three. The experimental were aimed to study the impact of compaction on soil properties at different depth for Orthosiphon Stamineus cultivation in order to determine the suitable soil classes, and propose best depth to plough the area to in order to have high yield with cost effective practice to manage the area.
Mississippi has a variety of different soils .The three general soils are 1) the river flood plain, known as the Delta, 2) a loess region, or bands of soils formed in windblown material that adjoins the Delta, and 3) Coastal Plain. The Mississippi Delta is better for growing row crop, while the loess and Coastal Plain region are better for animal production and forestry. The loess and Coastal Plain regions are divided based on similar soils, geology, climate, water resources, and land use called Major Land Resource Areas. The Mississippi Delta’s soil comes from sediments left by flooding various rivers in the region, rather than being a typical Delta formed by the mouth of a river. In the Delta most of the land is farmed, with three-fourths of the cropland to the north. Controlling surface water and drainage are major soil management issues. In the Delta soils are naturally diverse because of their alluvial origin. Particle sizes within the sediment decrease as distance from the originating stream increase. Another factor in Delta soil formation us surface water movement over time, because soils that formed under standing water have different properties than soils formed under moving water. Soils with large amounts of clay particles have unique features. When the soil is dry, small round aggregates form at the surface that look like shotgun buckshot, which is where the popular name for Delta clay soils “buckshot” came from. Soils with large clay content have very slow water filtration rates; this has led to significant aquaculture and rice production in the region. When floodwaters receded in the Delta, strong winds blew some of the dry sediment left by flooded river to the adjacent uplands to form the loess areas. Because of eas...
As we have observed throughout the centuries, colonialism has immensely shaped the majority of countries of modern society. In the essay “The Impact of Colonization and Western Assimilation on Health and Wellbeing of Canadian Aboriginal People”, Cathy MacDonald & Audrey Steenbeek developed significant points that reflect as connections to the essay “Virgin Soils Revisited” emphasizing the devastating impact colonialism has had on the wellbeing and health initiatives imposed on the Native Americans and the Aboriginal people of Canada to this day. Both indigenous populations have endured the hardships of poor health, racial issues such as oppression, and cultural assimilations due to the long-lasting effects of colonialism.
Once you have determined the feel of the soil (plastic, silty, sandy, or smooth) and made a ribbon, compare the length of the ribbon on the soil texture table to find out your soil
Dense to very dense natural and compacted foundation soils had settled a maximum of 4inches or four-tenths of a percent of the wall height. By the comparison of the
Soil liquefaction describes a phenomenon whereby a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid. The phenomenon is most often observed in saturated, loose (low density), sandy soils. This is because the loose sand has a tendency to compress when a load is applied; dense sands by contrast tend to expand in volume. If the soil is saturated by water, then water fills the gaps between soil grains. In response to the soil compressing, this water increases in pressure and attempts to flow out from the soil to zones of low pressure (usually upward towards the ground surface). However, if the loading is rapidly applied and large enough, or is repeated many times (e.g. earthquake shaking, storm wave loading) such that it does not flow out in time before the next cycle of load is applied, the water pressures may build to an extent where they exceed the contact stresses between the grains of soil that keep them in contact with each other. These contacts between grains are the means by which the weight from buildings and overlying soil layers are transferred from the ground surface to layers of soil or rock at greater depths. This loss of soil structure causes it to lose all of its strength. According to the
Compaction is a densification of the soil which reduces its biological activity, permeability, porosity, and water holding capacity, while at the same time increasing the risk of erosion due to accelerated run-off (13). While some soils are naturally compacted, mechanical pressure (i.e. heavy machinery) can compact soil (13). Erosion is a natural process which is actually essential in the soil formation process, but human activities have accelerated it (7). During erosion soil particles of the fertile topsoil are removed either by wind or water (i.e. runoff), this process is irreversible and can lead to the reduction of soil productivity (7).
Each type of soil has its characteristics in terms of water holding capacity. The first type is sand. Sand has the largest particles, with huge spaces between them, this is why sand doesn’t have the ability to hold water. Clay has the smallest particles compared to the other type, so it has good water storage qualities. It’s sticky to the touch when wet, but smooth when dry. () Clay has many fine pores, which gives it a higher capacity to hold water, than other types of soil. Eventually, it holds a higher amount of water than sand does.
Recompression method was developed by Bjerrum and Berre (1973) at the Norwagian Geotechnical Institute (NGI). In this method, soil specimens are reconsolidated to in-situ effective overburden pressure before sheared under undrained condition. Bjerrum mentioned that the principle behind this technique has been the swelling of sample that occurred before testing is so small and elastic in nature that the mechanical disturbance caused by such swelling can be eliminated by reconsolidating sample exactly as that it is in the in-situ stress condition before testing. Berre and Bjerrum (1973) highlighted that the volumetric strain during recompression should be less than 1.5 to 4%. This method should be used in the case of highly structured, brittle and sensitive clay with high quality sample. It is evident that the low plastic clay samples are found to be somewhat more disturbed than that of high plastic clay samples and reduced water content due to sample disturbance would cause gain in strength. On the contrary, increasing disturbance cause a reduction in strength and an increase in strain for the reconsolidated specimen at the verge of failure. Furthermore, there is some criticism on recompression method that the decrease in void ratio due to densification measure overestimating of strength even for bad quality sample.
The result for density of all mixtures with difference proportions of pure copper slag and spent copper slag shown in Table VIII and Table IX respectively. The density of cement-sand brick slightly increased as spent copper slag content was increased. The density of cement-sand brick was increased by almost 13.4% for mixture of replacement 60%PCS as fine aggregates, due to the fact that pure copper slag has higher specific gravity compared to the river sand.
Effect of overburden pressure. Soils of same density will give smaller count near ground surface.
Surface Creep occurs when landing sand particles remove the larger and heavier particles, pushing them forward.
The sand is free from clayey matter, salt and organic impurities. The sand is tested for its various properties like Specific Gravity, Fineness modulus, Bulk Density etc in accordance with IS 2386-1963. Fine aggregate passing through 4.75mm I.S. sieve and retained on 0.075mm I.S. sieve was used. It confirms to grading zone – II of I.S. 383-1970. The specific gravity and fineness modulus are found to be 2.50 and 2.79. These test results are tabulated in Table 4.1.4. Sieve analysis is carried out and results are shown in Table
... although we may never be able to understand exactly what soil failures can occur when a natural disasters take place, as time goes on and testing instruments and materials advance we will hopefully have a better understanding of what we can do to avoid soil failures and come up with a better and more sufficient method of improving the soils structure and strength permanently. While researching the information for this report I feel I have a much better understanding for construction geo-technics and foundations especially regarding the deformation, liquefaction and pile information related to this specific event. I hope to carry the information I have learned from this event into the construction field and apply them towards an authentic project that’s taking place and know that the information, regarding soils, I have given input on will be precise and accurate.