Primary and Secondary Consolidation
Settlement of saturated soils under increased loading consists of two successive phases, commonly referred to as the primary and secondary consolidation phases. The primary consolidation phase is dominated by pore pressure dissipation and effective stress increase; whereas, the secondary consolidation phase is dominated by creep (viscous deformation) at almost constant effective stress. The consolidation settlement consists of two parts. In conventional soil mechanics, Terzaghi’s theory of one dimensional consolidation is widely used despite some limitations.
In order to know the compressibility behavior of soil, we can make a plot of voids ratio versus log time using one dimensional consolidation tests as shown in figure 1.
Types of consolidation tests:
Conventional incremental loading test (Oedometer test)
Constant rate of strain test (CRS)
Calculation of settlement can be made as follows:
Total settlement (S)=C_c/((1+e_0)) log〖(P_v0^'+∆P)/(P_v0^' )〗+C_α/((1+e_0)) log〖t/t_p 〗
This equation assumes that the secondary consolidation settlement occurs after the dissipation of excess pore water pressure.
One of the most practical questions concerning consolidation is to know how to define the relevant consolidation curves for in situ conditions. The existence of creep during primary consolidation is evident, but there exist opposing opinions on the role of creep in the primary consolidation phase. Many researchers pointed out that, there are two extreme possibilities. Hypothesis A assumes that creep occurs only after the end of primary consolidation and consequently that the stress strain curve followed in situ is the same as the one obtained in the laboratory at the end of primary ...
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... the land reclamation. Finally, the consolidation process is not the only one controlling the rate of settlements in clay. Even when the excess pore water pressure has completely dissipated, the settlement continues, which is called creep or secondary compression. Towards the end of primary consolidation, a contribution of the secondary compression becomes more pronounced and may produce significant increases in settlements long after the primary consolidation is over.
It is important to remember that the consolidation process is not the only one controlling the rate of the settlements in clay. Even when the excess pore water pressure has completely dissipated, different physical phenomena cause continued settlement. While this secondary compression is present from the beginning of the consolidation process, towards the end of primary consolidation its contribution
Lithologically the Kimmeridge Clay Formation can be subdivided into four units (Figure 2), despite of beds at the base of the succession are poorly exposed. However, in contrast, the units from mid-eudoxus Zone to the top of the formation that are well seen in the Formation. At the base of the formation until the eudoxus Zone, the strata are made up almost entirely of bioturbated shelly clays and in between beds, horizons of oil and bituminous are present. The upper part of the Eudoxus Zone until the upper Pectinatus Zone the composition is kerogen-rich mudstones and coccolith limestone.
3. 120 MY : Continued erosion of the land as it is slowly uplifted and
Desert pavements are common landforms in arid regions. They consist of flat or sloping surfaces where stones are closely packed angular or rounded, and generally exhibit low relief (Mabbutt, 1977). Pavements tend to form on both alluvial fan toposequences and on weathering volcanic flow fields in arid regions. Soils are often found under desert pavements and they play an important role in the evolution of pavements (McFadden et. al., 1987). In the past there have been several theories as to the formation pavements and soil development beneath them. Deflation, or the erosion of finer grained particles from a surface, stone concentration by wash erosion and upward displacement of stone due to shrink and swell clay characteristics were at one time believed to be the main factors in the formation of desert pavements (Mabbutt, 1977). However, more recent research has shown that desert pavements are born and maintained at the surface, and that the soil below them is mainly eolian in origin. Slow accretion of eolian dust below the pavement is a process that eventually develops cumulate horizons. Eolian dust in environments where pavements often develop is rich in carbonate salts and clays due to the fact it often originates from nearby playa lake evaporate basins (McFadden et. al., 1987). Soils that form below the pavements over time develop calcic horizons and clay rich structure due to the influx of these eolian fines through the pavement surface. In turn the development of mature or plugged calcic horizons effects the form of the pavement surface because it alters the water drainage infiltration rate and causes pavements to decline.
A representation of the slow decrease in flux that can result from consolidation of the fouled layer is presented in figure 2.4.
Consolidation is a key word being used by many in the Fire Service today. Whether it is consolidation of equipment, manpower, stations, or just Standard Operating Procedures (SOP's). The reason for this change is due to the economic slowdown that we are all currently facing on every level, personal, business, and governmental. When this occurs the tax payers start to look at how their tax dollar are being spent. To assist in spending those tax dollars wisely the fire service has begun to investigate how to consolidate without losing services.
Porosity is the amount of air space in a soil. There are two types of
of sand and gravel deposits that lay on top of London clay and it is
• Compaction is done in a rectangular or triangular pattern in a number of phases, each phase has a number of passes, it could be a primary pass, or secondary pass, …etc.
Mergers and acquisitions immediately impact organizations with changes in ownership, in ideology, and eventually, in practice. There are multiple reasons, motives, economic forces and institutional factors that can, taken together or in isolation, influence corporate decisions to engage in mergers or acquisitions. The financial risks of merging with or acquiring an organization in another country and how those risks can be mitigated are important issues for corporations to conduct research on. This paper will examine the sensible and dubious reasons for mergers and acquisitions and the benefits and costs of the cash and stock transactions.
Surface Creep occurs when landing sand particles remove the larger and heavier particles, pushing them forward.
Clay soils are usually referred to as very cohesive, as they retain a measurable shear resistance (a materials ability to resist forces that can cause the internal structure of a material to slide against itself), in the absence of confining forces. The ability of a cohesion-less or frictional soil such as sand or silt to support a building depends on the friction between its particles. Sand confined by surrounding soil within the earth can support a heavy building, whereas a conical pile of sand on the surface of the earth can support nothing, because there is little or no shear resistance between the particles.
This step is followed by Mixing to break big lumps and to homogenize the softened clay mixture. The mixing could be done mechanically, by the use of some ani...
... 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.
Erosion causes floods, silting up of water reservoirs, disruption of communication systems, and disturbance of the social-economic setup of the farming community. Erosion can be categorized into two parts: normal, or geological erosion, and accelerated erosion. ("Soil erosion- causes," 1987). With normal erosion, the effects are not visible on the land surface and soil productivity is not adversely affected. The amount of soil lost through this kind of erosion is equal to the amount of soil formed. With accelerated erosion, however, the effects of erosion are visible on the ground surface and the rate of soil loss is greater than the rate of soil formation ("Soil erosion- causes," 1987).
The zero air voids (ZAV) line is the combination of moisture and density that produce complete saturation of the soil or the γd obtained when there is no air in the void spaces. The compaction curve theoretically does not cross this line but becomes parallel to it. Remember that the values of water content, wet unit weight, and specific gravity are not constant throughout the soil. There could also be variability in the test results. Variability can result in points on the compaction curve above the ZAV line (S > 100%). These data points should not be thrown out.