SOIL MECHANICS/GEOTECH
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The average N60 blow count =6 in the effective zone for a footing…
Question The average N60 blow count =6 in the effective zone for a footing located at D = 1.6m (blow count in range from 1-to 4m depth). What is the allowable bearing capacity for a 40mm settlement? present data as a table of qa versus B. Solution to The average N60 blow… What causes differential settlement? Differential settlement is caused by a number of factors, including: Type of soil: Differential settlement is most commonly caused by differences in the type of soil beneath a foundation. For example, sand will settle more than clay. Moisture in the soil: Soil that is too dry or too wet will settle more than soil that is at a moderate moisture level. Weight on the soil: A foundation that is too heavy or has too much weight on it will settle more than a lighter foundation. Size and depth: Size and depth of the foundation can also affect differential settlement. For example, a shallower foundation will settle more than a deeper foundation and a larger foundation will settle more than a smaller foundation. Shape of the foundation: A foundation that is not level or has an irregular shape will settle more than a level foundation with a regular shape. What causes soil settlement? Geotechnical settlement is typically the result of loading (from a building or vehicles moving along on a road, for example) exceeding the ground’s bearing capacity. Due to site ground pressures, pore water pressure increases and then dissipates, causing consolidation settlement, where the soil beneath the structure moves vertically and horizontally. Weak and poorly compacted soils are particularly vulnerable. Soil settlement can be caused by other factors too, such as changes in soil moisture content, for example, saturated cohesive soils may soften or drier cohesive soils may shrink. Deep excavations and tunneling, plus the collapse of naturally occurring voids or abandoned mine workings, are also key factors in causing different types of settlement. Settlement occurs immediately after a load is applied or take years, depending on the underlying soil conditions Geotechnical engineers often carry out settlement analysis prior to construction to analyze the ground conditions and recommend foundation solutions for preventing settlement in the future.
Solved: A series of unconfined compression tests in the zone of …
Question A series of unconfined compression tests in the zone of interest (from SPT samples) from a boring-log give an average qu = 200kpa. The soil is fully saturated (∅=0). Estimate the allowable bearing capacity for square footing located at somewhat uncertain depth (let D =0m) and B dimensions unknown using both the Meyerhof and terzaghi bearing-capacity equations. use safety factor SF =3.0. Solution
Solved: A square column foundation (figure 6.12) is to be construc…
Question A square column foundation (figure 6.12) is to be constructed on a sand deposit. The allowable load Q will be inclined at an angle β =20° with the vertical. The standard penetration numbers N60 obtained from the field are as follows. Determine the Q. Using FS = 3. Depth (m) N60 1.5 3 3.0 6 4.5 9 6.0 10 7.5 10 9.0 8 See a related number
A series of large-scale footing bearing-capacity test were…
Question A series of large-scale footing bearing-capacity test were performed on soft saturated clay (∅ = 0). one of the tests consisted of a 1.5m square footing at a depth D = 1.5m. At a 25mm. settlement the load was approximately 16.1 tons from intersection of a given load-settlement curve. unconfined compression and shear tests gave values as follows: ∂u =3.0t0n/m2, c = 1.92ton/m2, the unit weight of soil is 17.5KN/m3. Compute the ultimate bearing capacity by Hansen and compare with the load-test value of 16.1tons. Solution to A series of large-scale footing… Immediate settlement The load causes instant changes in the soil stresses, and reduces soil voids, as soon as the load is applied. What causes soil settlement? Geotechnical settlement is typically the result of loading (from a building or vehicles moving along on a road, for example) exceeding the ground’s bearing capacity. Due to site ground pressures, pore water pressure increases and then dissipates, causing consolidation settlement, where the soil beneath the structure moves vertically and horizontally. Weak and poorly compacted soils are particularly vulnerable. Soil settlement can be caused by other factors too, such as changes in soil moisture content, for example, saturated cohesive soils may soften or drier cohesive soils may shrink. What causes soil settlement? Geotechnical settlement is typically the result of loading (from a building or vehicles moving along on a road, for example) exceeding the ground’s bearing capacity. Due to site ground pressures, pore water pressure increases and then dissipates, causing consolidation settlement, where the soil beneath the structure moves vertically and horizontally. Weak and poorly compacted soils are particularly vulnerable. Soil settlement can be caused by other factors too, such as changes in soil moisture content, for example, saturated cohesive soils may soften or drier cohesive soils may shrink. Deep excavations and tunneling, plus the collapse of naturally occurring voids or abandoned mine workings, are also key factors in causing different types of settlement. Settlement occurs immediately after a load is applied or take years, depending on the underlying soil conditions Geotechnical engineers often carry out settlement analysis prior to construction to analyze the ground conditions and recommend foundation solutions for preventing settlement in the future. A series of large-scale footing
A square footing that is vertically and concentrically loaded is to be
Question A square footing that is vertically and concentrically loaded is to be placed and cohesion-less soil as shown in the figure. What is the allowable bearing capacity with factor of safety of 3 using terzaghi method. Assume the water content of soil adjacent to ground surface is about 10%. see another with factor of safety of 2.5 Solution
A square footing that is vertically and concentrically loaded is to be
A square footing that is vertically and concentrically loaded is to be place on a cohesion-less soil as shown in the figure below, the soil and other data are given below. What is the allowable soil bearing capacity using terzaghi’s equation and factor of safety =2.5. See another with a factor of safety of 3 Solution
Solved: A square footing of size B x B is required to carry a gross
Question A square footing of size B x B is required to carry a gross allowable load of 670 kN. The base of the footing is to be located at a depth of 1 m below the ground surface. The soil properties are as follows: γ = 18.1 kN/m 3 , c = 0, Φ = 40˚. If the required factor of safety is 3, determine the size of the footing using Terzaghi’s bearing capacity factors and general shear failure of the soil. Solution
Solved: Assume that the shear strength parameters of the soil are the
Question Assume that the shear strength parameters of the soil are the same in the previous number, a square footing measuring BXB will be subjected to an allowable gross load of 1000KN with Fs =3 and Df =1m, Determine size B of the foundation. Solution
A square footing is 2x2m in plan. The soil supporting the foundat…
Question A square footing is 2x2m in plan. The soil supporting the foundation has a friction angle ϕ′=25∘,c′=20kN/m2,the unit weight of soil γ=16.5kN/m3. Determine the allowable gross load on the foundation using terzaghi bearing capacity equations with a factor safety of 3. Assume that the depth of the foundation (Df)=1.5m and the general shear failure occurs in the soil. Solution