factors affecting consolidation of soil

Soil Settlement. ) and hydraulic conductivity ( Figure 6.1 (a) and (b) show fixed ring type and floating ring type consolidometer set up. Terzaghi had an engineering approach to the problem of soil consolidation and provided simplified models that are still widely used in engineering practice today, whereas, on the other hand, Fillunger had a rigorous approach to the above problems and provided rigorous mathematical models that paid particular attention to the methods of local averaging of the involved variables. In coarse-grained soil like gravels and sands, secondary consolidation is negligible. Effective stress. c d {\displaystyle C_{S}} The application of the load causes deformation of the loading frame, the porous stones and the soil sample. 5. It is the portion of the settlement which occurs immediately after application of load. The rate at which this process of consolidation proceeds depends upon a number of factors such as the soil properties, the layer thickness and the boundary conditions. The highest stress that it has been subjected to is termed the "preconsolidation stress". Some types of soil, mainly those rich in organic matter, show significant creep, whereby the soil changes volume slowly at constant effective stress over a longer time-scale than consolidation due to the diffusion of water. //]]>. The permeability of the specimen at any stage of loading can be measured only in the fixed ring type. Dessication of soil. 2 Conf., Taipei, Vol. However, in soils with a high amount of organic material such as peat, the phenomenon of creep also occurs, whereby the soil changes volume gradually at constant effective stress. For normally consolidated clays the index commonly ranges between 0.20 to 0.50 and for silts between 0.16-0.24. TOS 7. Effect of capillary pressure which is later destroyed by the rising of the water table. C Causes of Over-consolidation or Pre-consolidation are: Parameters involved in the calculation of Consolidation of soil: Coefficient of Compressibility (av): It is the ratio of change in void ratio to the change in effective stress. But in the fixed ring test, the soil moves only downward, relative to the ring. C Agricultural Land Consolidation (ALC) is an effective tool to ensure national food security. 2 e {\displaystyle K} + Land consolidation of dryland-to-paddy conversion for improving tillage conditions and grain production capacity is widely implemented throughout the world. These volume changes may be brought out by two distinct processes. 0 This process is started when the soil is fully saturated. 4. PPT of Professor N. Sivakugan, JCU, Australia (www.geoengineer.org/files/consol-Sivakugan.pps). {\displaystyle \lambda } The methods are also known as time fitting method. In case of compaction, the soil mass is applied with a dynamic load for small interval of time. The proximity of trees with large roots. With vacuum pressure, the inevitable unsaturated condition at the soil-drain interface may be improved, resulting in an increased rate of consolidation. Create a free account and view content that fits your specific interests in geotechnical engineering. e The straight portions P1Q1 and S1T1 on either side of O1 are referred as the virgin compression curve. the construction of a building or an embankment above a soil mass) or even the decrease of the ground water table. So the change in volume is equal to the change in depth. The diameter of the specimen used should be from 65 to110 mm and thickness of the specimen should be 15 to 30 mm is used. Coefficient of consolidation is the indicative of the combined effect of compressibility and permeability of soil on the rate of volume change. v The factors affecting the consolidation rate of the foundation are analyzed and the following conclusions are reached: (1) Increasing the cement soil pile displacement ratio and compression modulus can accelerate the consolidation process of the composite foundation, which is consistent with other research results. The type of rock the soil originated from, topographic features of an area, climate, time and human activity are the five major factors that affect soil composition. Rate of settlement is the time in which some percentage of total settlement occurs. Foundation Settlement For a given soil at a given void ratio, cv increases with increasing magnitude of the consolidation pressure. Over consolidated soils are less compressible and have greater shear strength and more stability. [2], Consolidation is the process in which reduction in volume takes place by the gradual expulsion or absorption of water under long-term static loads. (iii) Expulsion of water and air from the void of the soil mass. 7. Whenever a soil mass is stressed, it deforms. <> U(H>=o#rbH B_=V R:GM"&8#Btjq("UV/w k+W!D^8&?b>E( Language: English. Soil deformation may occur by change in stress, water content, soil mass, or temperature. This can be expressed in the following equation, which is used to estimate the volume change of a soil layer: In general, consolidation in sandy soils is a quick process (occurring possibly immediately during construction) whereas the process may last for many years or even decades in clay soils. When the soil is dense and of low porosity, roots have a harder time digging down through compacted layers to take hold. Geotechnical engineers use oedometers to quantify the effects of consolidation. The procedures of fixed ring tests are explained below: 1. The process of consolidation is often explained with an idealized system composed of a spring, a container with a hole in its cover, and water. Ranjan, G. and Rao, A.S.R. Figure 6.3 (b) shows the plot of effective pressure vs void ratio on semi log graph paper. 0 C The compressibility of soil is defined as the capability of soil to decrease its volume under mechanical loads, whereas the consolidation is the compression of saturated soil under steady pressure and it is occurred as a result of water expulsion from the soil voids. log Heave problem is particularly common in arid regions. The compressibility of saturated specimens of clay minerals increases in the order kaolinite

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