soil consolidation example problems

Consolidation plays an important role in many soil mechanics problems. Courses » Teaching & Academics » Engineering » Geotechnical Engineering » Soil Mechanics Solved Examples – Consolidation. The building has a basement and is founded on raft foundation. Search. The properties of the two layers are their thicknesses h 1 and h 2 and permeabilities k 1 and k 2 and a uniform compressibility m v for both layers. While watering the foundation, foundation design and plumbing problems each contribute to a lot of foundation problems, soil consolidation is the root cause of many foundation problems. solve the soil consolidation examples with nonassociated plasticity, and their performances are investigated and compared. 1.6 Consolidation Test 1.6.1 General - Consolidation can be defined as a dissipation process of excess pore pressure induced by applied load or change of boundary conditions. - It is a time dependent behavior of soil deformation. One-Dimensional Consolidation Problems. The column of soil is assumed to be in equilibrium under self weight and a surcharge of 10 kPa. In analyzing real problems using the classical theory of one-dimensional consolidation it is necessary to make a number of simplifying assumptions, the effects of which cannot be determined easily. This is ... nonlinear consolidation problems using mixed finite element formulations. The distance of consolidation is determined using this equation: Where: s = settlement. Two solution schemes are proposed and compared for large 3D soil consolidation problems with nonassociated plasticity. 4.1 ☆☆☆☆☆ 4.1/5 (12 reviews) 1,825 students. The following example problem is considered here. A quasi-analytical method is newly introduced to solve the equal-strain consolidation problem of multilayered soil with a vertical drain system. The stress from the building at the foundation level is as shown in the figure. Victor N. Kaliakin, in Soil Mechanics, 2017. 3. Determine the mass of the ring and the soil sample. 2. Soil consolidation, which we can think of as a settling phenomenon, is a problem because of our clay soil. At the end of test, the sample height was 13.3 mm and the oven dry weight of soil was 78.3 g. Assuming Gs = 2.66, find: (i) The initial void ratio, eo (ii) Final void ratio, ef (iii) Total sample strain εf 4. 1. • 1 Dimensional Consolidation 2 Problem Deﬁnition Figure 1 shows the problem to be analysed. As clay soil consolidates or settles, it loses its ability to support the foundation. A porous disc of the same size, of the soil as specimen is placed above and below the soil specimen to represent the pervious (drainage) soil layer in the field. Examples on total consolidation 19,434 views. Each footing will carry 122.5 kips. Soil Mechanics – Third Year Civil Eng.Soil Mechanics (PBW N302) Example Compute the settlement due to compressibility of the sand and clay layers at points (a) and (b) of the building shown in the figure. The problem will be illustrated for the situation shown in Fig. As in the one-dimensional Terzaghi consolidation solution (see “The Terzaghi consolidation problem,” Section 1.14.1 of the ABAQUS Benchmarks Manual), the problem is run in two steps.In the first *SOILS, CONSOLIDATION step, the load is applied and no drainage is allowed across the top surface of the mesh. (11.17). Share; Like; Download ... Malika khalil. ⇒ Significant in saturated clayey soils. Design Problem for Consolidation and Time Rate of Settlement It is proposed to place a foundation on top of the existing soil with the described profile. 5.5. Follow Published on Mar 20, 2018 ... Settlement o ' o o c c σ' σΔσ log e1 Hc S ′+ + = mm228m228.0 194.629 120194.629 log 1.1871 7*0.342 Sc == + + = Example 11: Soil investigation at a site gave the following information. After 62 days, a point 2.0 m below the top of the clay layer has a degree of consolidation of 70%. Learning … 2. Consolidation is a form of settlement where the air and liquids in a soil (the voids) are removed due to pressures acting on the soil. The clay layer is drained only from the top boundary. Soil Consolidation Curve Log σ’ e e 2 σ’ 2 Virgin compression (slope c c) Unloading or rebound line (slope c r) σ’ 1 e 1 σ’ 3 e 3 e r Oedometer Test on Soil Sample Log σ’ e Virgin compression (slope c c) Unloading or rebound line (slope c r) σ 1= σ’ vfield= c e 3=e field e r=e 0 e 4 e r2 Δσ σ 2=σ + Δσ Assemble the apparatus using filter papers be tween the soil and the porous stones, balance the lever arm, and set the dial indicator to zer o. Apparatus. Finally, some useful observations and conclusions are summarized in Section 5. Secondary consolidation may be the larger component if settlement in some soils, particularly in soils with a large organic component. Only the soil surface is allowed to drain. Example Problems Related to Time Rate of Consolidation. There is two-way drainage, upward and downward. The average height of the sample in the 1D test was 0.375 inches at the time of this load increment. Calculations for the amount of time for settlement to occur in clay soils This section is a continuation of the consolidation section in soil mechanics analysis. For the example presented previously, if different components of permeability are considered individually while leaving the other components for subsequent analyses, this may lead to erroneous results in view of average degree of consolidation. Two Major Problems with soil settlement analysis are: ... At the end of secondary consolidation the soil has reached a new K o-state (at-rest state). The coefficient of consolidation C v = 8.0 X 10-8 m2/s. Soil Mechanics Solved Examples – Consolidation. For consolidation settlement, the rate of void ratio SS= i ++S c S s Patrick J. where ρ is the compression (decrease in the thickness of soil due to consolidation) at any given time and p f is the final settlement at the end of consolidation given by Eq. A consolidation test was performed on a sample with initial dimensions of H = 20 mm and ring diameter = 63 mm. Example. 10.3 CONSOLIDATION AS A SEEPAGE PROBLEM The seepage of water from the soil during consolidation may be represented by means of a head diagram of the type shown in Fig. 3. Permeameter mold – of 1,000 ml capacity, 100 mm diameter, and 12.73 mm in height. Sharpen your problem-solving skills on the topic of soil consolidation. Calculate the time required for (a) 90% consolidation settlement, (b) a settlement of 100 mm. Water at particle contacts intergranular contact force due to surface tension Shrinkage caused by drying Consolidation: transient flow of water. 9.2 Terzaghi's One-Dimensional Consolidation Theory . (11.14) through Eq. Soil Properties & Soil Compaction Page (6) Solved Problems in Soil Mechanics Ahmed S. Al-Agha 3. The test results for this load increment are plotted with log time and square root of time in Figure C. Determine the coefficient of consolidation for this soil using the log time method. Sharpen your problem-solving skills on the topic of soil consolidation. A soil specimen is cut from the undisturbed soil sample to the size of the internal diameter of the consolidation ring and is placed into the consolidation ring. Compaction equipment – suitable dynamic or static compaction equipment. The data helps to determine the compression and recompression index, coefficient of consolidation and coefficient of secondary consolidation, as well as the preconsolidation pressure. ⇒ Factors on consolidation time 1) Degree of saturation One solution scheme results in the nonsymmetric linear equations due to the Newton iteration, while the other leads to the symmetric linear systems due to the symmetrized stiffness strategies. The soil layer is subjected to an uniform loading of the intensity p0acting on the surface. Clay 1 and Clay 2 due to 150 kPa net foundation loading. Equipment Used. Figure 1. The total consolidation settlement of a 8.0 m thick clay layer is estimated to be 49 cm due to application of a particular surface load. 12. The birth of soil mechanics as a modern engineering discipline occurred in the 1920s. Base of the soil is rigidly ﬁxed while the sides are laterally constrained. The consolidation problem of soil has always been one of the key problems of soil mechanics, for it has close relation with the deformation, strength, stability, and seepage of soil mechanics. If a soil sample has distinct gaps in the gradation curve, e.g., a mixture of gravel and fine sand, with no coarse sand, ... Later sections of this article address the pore water pressures for seepage and consolidation problems. The final consolidation settlement of a layer of clay 5.0 m thick is calculated to be 280mm. The coefficient of consolidation for the loading range is 0.955 mm²/min. using elastic theory for cohesive soils such as clays. Input ﬁle(s): soil 1d consolidation.dat 1 Problem Description In the following example a one-dimensional consolidation problem has been analyzed. The test will be completed on three unsaturated soil, To determine the shear strength of the soil by Unconsolidated Undrained test Significance and Applications вЂў Prior to testing, avoid any moisture loss in the sample, place on a triaxial base (acrylic). A 4 ftlayer of sand fill will be placed above the base of the footing. 46% 61% 61% 100%. Example A 12 m thick clay layer is doubly drained (This means that a very pervious layer compared to the clay exists on top of and under the 12 m clay layer. Coupled Linear System of Equation Arising from Elastoplastic Biot’s Consolidation Problems Soil consolidation is a soil settlement process coupled with dissipation of excess pore … To determine the permeability of a given soil sample using a falling or constant head permeameter. Ignore the immediate settlement, and calculate total consolidation settlement of soil profile composed of two different types of clay, i.e. The problem to be considered is the consolidation of a soil consisting of two layers; see Figure 5. Since Terzaghi [ 1 ] published his consolidation theory in 1925, noteworthy process has been achieved in consolidation theory. 2. This test is designed to determine the rate and magnitude of volume decrease that a soil sample undergoes when subjected to different vertical loads. As an example to illustrate the parameters that affect the consolidation of soil using PVDs, Hansbo’s equation (Hansbo, 1981) is written as follows U h ¼ 1 exp 8T h F(n) 1: F(n) ln(n) 0:75þ ln(s) k h k s 1 problems. It is a column of saturated soil of depth 10 m. The water table is at the top in line with the ground level. 10.5., in which a compressible clay is sandwiched between two relatively Consolidation can occur over a long period of time and can destroy structures if not address soon enough. The soil profile below the footings consists of 8 ft. of sand underlain by 8 ft. of clay with rock bencath the clay layer. Fox Purdue University. Both consolidation and secondary compression settlement components are time-dependent and result from a reduction of void ratio and concurrent expulsion of water from the voids of the soil skeleton. This section will give you formulas and quantitative example problems that you might see on the exam. Of saturation Sharpen your problem-solving skills on the surface at the top of the sample in the Figure plasticity. Large organic component consolidation Examples with nonassociated plasticity, and their performances are investigated and compared large... 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