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Consolidation
Published in Jonathan Knappett, R. F. Craig, Craig’s Soil Mechanics, 2019
Jonathan Knappett, R. F. Craig
Consolidation settlement is the vertical displacement of the soil surface corresponding to the volume change at any stage of the consolidation process. Consolidation settlement will result, for example, if a structure (imposing additional total stress) is built over a layer of saturated clay, or if the water table is lowered permanently in a stratum overlying a clay layer. On the other hand, if an excavation (reduction in total stress) is made in a saturated clay, heave (upward displacement) will result in the bottom of the excavation due to swelling of the clay. In cases in which significant lateral strain takes place there will be an immediate settlement due to deformation of the soil under undrained conditions, in addition to consolidation settlement. The determination of immediate settlement will be discussed further in Chapter 9. This chapter is concerned with the prediction of both the magnitude and the rate of consolidation settlement under one-dimensional conditions (i.e. where the soil deforms only in the vertical direction). This is extended to the case when the soil can strain laterally (such as beneath a foundation) in Section 9.5.
Consolidation, stress distribution, and settlement
Published in Hsai-Yang Fang, John L. Daniels, Introductory Geotechnical Engineering, 2017
Hsai-Yang Fang, John L. Daniels
Consolidation processes tend to control the engineering properties of compressible soils, have a dominating influence on their strength, and govern the rate and magnitude of settlement that occurs when such deposits are subjected to load. There are three general types of consolidation phenomena in clay deposits existing in the natural condition namely (a) normally consolidation, (b) overconsolidation, and (c) underconsolidation. In most case, the soil deposit is normally consolidated. Figure 9.1 shows the difference between normally and overconsolidated soil deposits in laboratory standard consolidation test. An overconsolidated soil deposit has a complex failure mechanism but is generally desirable from a construction perspective. In the following sections all three types of consolidation phenomena will be discussed with emphasis on the normally and overconsolidated consolidation soil deposits.
Three-dimensional excavations
Published in William G. Pariseau, rd Edition, 2017
Materials may have a large porosity because of relatively high percentage of voids, but if the voids are very small, then permeability will be low and seepage velocity small. A high porosity does not necessarily mean high permeability because of the role of void size. Clays and shales are often very porous but also have very low permeabilities because of the small particle and therefore small void size. In soil mechanics, consolidation refers to soil settlement in response to exudation of the pore fluid, usually water. The rate of consolidation depends on permeability. Porosity is more indicative of the amount of fluid stored in the pores. Clays may require decades to become fully consolidated in response to loads imposed by buildings and other structures that are completed in just a few years. Surface settlement also occurs in response to removal of fluids such as oil and water from strata below the surface.
Uncertainty in differential settlements of bridge foundations and retaining walls
Published in Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 2020
Naresh C. Samtani, John M. Kulicki
Immediate settlement occurs in all geomaterials regardless of whether they are cohesive or cohesionless. Consolidation settlement typically occurs in fine-grained cohesive soils that are saturated at the time additional loads are applied. The one-dimensional (1-D) consolidation theory (Terzaghi and Peck, 1967) is most commonly used to predict consolidation settlement. Assuming the consolidation parameters (e.g. compression index, coefficient of consolidation, etc.) are determined from representative undisturbed soil samples and consolidation tests, AASHTO has elected to use a SE load factor, γSE of 1.0.
Application of the SBAS-DInSAR technique for deformation monitoring in Tunis City and Mornag plain
Published in Geomatics, Natural Hazards and Risk, 2020
Anis Chaabani, Benoit Deffontaines
According to Terzaghi (1923), the phenomenon of consolidation is the result of the reduction of the water content of a saturated soil and provides that air does not replace water.The static charges exerted on the ground in the long term, induce the elimination of the interstitial water and thus it causes a settlement. This consolidation process mainly affects saturated clays because of their low permeabilities.
Assessment of Geotechnical Properties of Oil Contaminated Subgrade Soil: Review
Published in Soil and Sediment Contamination: An International Journal, 2022
Walied A. H Elsaigh, Johnson Rotimi Oluremi
Consolidation is the time-dependent rearrangement of soil particles with reduction in voids and pores (settlement) and the expulsion of water (seepage) under the stress initiated by compressive force, which consequently leads to increase in strength in a saturated soil. It is of importance since it controls the serviceability state of the civil engineering structures. Investigation of Hamidi and Jedari (Hamidi and Jedari 2011) on effect of kerosene or gas-oil contamination (0, 3, 6 and 9 wt%) on geotechnical properties of kaolinite and bentonite soil materials showed that with increase in contamination level, there was an increase in the values of one-dimensional compressibility coefficient of the soil materials. This implies the nature of soil might contribute to the consequential effect of the hydrocarbons on the geotechnical properties of the soil. Similarly, Kermani and Ebadi (Kermani and Ebadi 2012) affirmed that with the increase in crude oil content, the compressibility of the soil increased as signified by the reduction of the void ratio under maximum load of 1300 kPa, refer to Figure 5, which is consistent with the research work by Meegoda and Ratnaweera (Meegoda, Ratnaweera, and Ratnaweera 1994) and Rehman et al. (Rehman, Abduljauwad, and Akram 2007) except at 12% petroleum content where it increased. It is worth noting that unavailability of water content to the double layer water might make the soil matrix collapsed under load, which is reflected at 12% with increase in void ratio. Karkush and Abdul-Kareem, (Karkush and Abdul-Kareem 2017) also examined the void ratio, compressibility as well as the permeability of the oil contaminated soil using consolidation test. There was reduction in void ratio from 0.34 to 0.26% for increase in petroleum content from 0 to 20% (Figure 5). This really reflected occurrence of increase of compressibility of the soil, but, as explained by the authors, the coefficient of consolidation, which measures the degree of compressibility, slightly decreased with consequential increase in permeability due to the bouncing back of the soil leading formations of larger pore sizes from aggregation of soil particles into pseudo-size under the coating effect of fuel oil.