Concept explainers
A 1.5 m square footing carries a column with a service load of 105 kN. It is founded at a depth of 2 m on a medium stiff clay with an undrained shear strength of 42 kPa, an overconsolidation ratio of 4, and a plasticity index of 35. The clay layer is 5 m thick and overlies a very stiff shale. Estimate the undrained settlement of the footing using the generalized elastic method with Christian and Carrier’s (1978) influence factors.
The undrained settlement of the footing using the generalized elastic method with Christian and Carriers (1978) influence factors.
Answer to Problem 8.1QPP
3.1 mm
Explanation of Solution
Given data:
Size of footing = 1.5m
Service load = 105kN
Depth = 2m
Undrained shear strength = 42kPa
Overconsolidation ratio = 4
Plasticity index = 35
Thickness of clay layer = 5m
Formula used:
The ratio of depth to width of footing is
The influence factor accounting for depth of footing from the following figure is
The aspect ratio of footing is
The relative thickness of compressible layer is
The influence factor accounting for shape of footing and compressible layer thickness from the above figure is
The average soil modulus over depth of compressible layer is
Substituting the values in the above equation,
The undrained settlement of the footing is
Conclusion:
The undrained settlement of the footing is 3.1 mm.
Want to see more full solutions like this?
Chapter 8 Solutions
Foundation Design: Principles and Practices (3rd Edition)
- A 1.8 m square, 2 m deep footing supports a service load of 570 kN. It is supported on a clayeysand. A dilatometer test run at the site has returned the following modulus profile.Depth (m) 2 3 4 5 6 7 8 9 10 11 12M (MPa) 7.7 8.8 10.2 14.8 15.4 10.8 11.6 11.6 13.1 13.8 13.4Compute the footing settlement.arrow_forwardA long footing 2 m wide is located in the level area at the top of a long, 45° slope where clay soils exist. The slope height is greater than the footing width. The soil unit weight is 17.5 kN/m3, and the cohesion shear strength is 65 kPa. The D/B ratio is 1, and the b/B ratio is also 1. What loading can be imposed onto the footing per meter of length (using a factor of safety of 3 with the bearing capacity equation appropriate for footings along the top of slopes)?arrow_forwardA circular footing with a 1.5 m diameter is to be constructed 1.22 m below the ground surface. The subsoil consists of a uniform deposit of dense soil having the following strength parameters: Angle of Friction = 250 Nc = 24.1 Nq = 13.1 Ny = 9.1 Cohesion = 48 kN/m2 Unit weight of soil = 20.12 kN/m2 The groundwater table is at a great depth and its effect can be ignored. Determine the following: a) Ultimate bearing Capacity of the soilarrow_forward
- Exl: A footing is uniformly loaded with q = 100 kN/m² as shown in the figure. Compute the vertical stress increments under Points A, B, at z = 10 m. 13.5 m 7.0 m Footing 12 m (Plane view) 6.0 marrow_forwardA rectangular footing 3m x 4m carries a column load of 800kN at a depth of 1.6m. The footing rests on soil strata of X m thick and having a unit weight of 19 kN/m3, Poisons ratio of 0.45, and Young's modulus of elasticity as 35000 kN/m2. If the footing is considered flexible, estimate the immediate elastic settlement below its center. If X = 3.5arrow_forwardA footing of size 2m×2m transferring a pressure of 200 kN/m², is placed at a depth of 1.5 m below the ground as shown in the figure (not drawn to the scale). The clay stratum is normally consolidated. The clay has specific gravity of 2.65 and compression index of 0.3. 1.5m 1m 1.5 m 200 kN/m² Silty sand Clay Ya =15kN/m³ Y sat = 18kN/m³ Y sat = 17 kN/m³ GWT $0.5 m Dense sand Considering 2:1 (vertical to horizontal) method of load distribution and Y₁ = 10kN/m³, the primary consolida- tion settlement (in mm, round off to two decimal places) of the clay stratum isarrow_forward
- Problem 1 A 3m x 3m square footing is constructed at a depth of 2m in a 26m deep clay layer with following soil properties: g =16.5kN/m3, Normally Consolidated Clay, eo= 0.65, Cc = 0.25,ms=5 and Es= 6.0 MN/m2. If there is a 1000kN structural load on the footing, calculate the consolidation settlement of the footing. A 2m X 2m footing carrying 1400kN load is constructed in a site with 2.5m thick clay layer under a 2.5m thick sand layer. If the footing and the ground water table are located at 1.5m below the surface, calculate the consolidation settlement of the footing. You may assume the following soil properties: for sand gsat = 19.25kN/m3 and gt = 7kN/m3, and for clay eo= 0.65, Cc = 0.25, Cs = 0.06, s’p = 200kN/m2 and gsat =19.25kN/m3. A 1882kN load is carried by a 2.6m x 2.6m square footing at a depth of 1.4m in a 30 m deep sand layer. Given the following soil properties for soil calculate the total settlement of the footing after 10 years. Where soil properties are: g = 15.9…arrow_forward4. A square footing having a dimension of 3 m x 3 m carries an axial load of 1500 kN. The bottom of the footing is 2 m from the ground surface consisting of a layer of sand overlying a 4 m laye of clay. The water table is located 2 m below the ground surface. Dry unit weight of sand = 16.5 kN/m³ Saturated unit weight of clay = 20 kN/m³ Void ratio of clay = 0.80 Liquid limit of clay = 50% a. Compute the increase in vertical pressure. b. Compute the overburden pressure (effective pressure) at the midpoint of clay. c. Compute the primary consolidation settlement. 2m 4 m Sand 1500 KN 3m x 3 m Clay (normally consolidated) Ya 16.5 kN/m² 7sat 20 kNm' e = 0.80 LL = 50 | }arrow_forwardThe square footing shown in the figure carries a load of 3500 kN. Assume that the stress below the footing is distributed at a slope of 1H:2V. The clay layer is overconsolidated with OCR=2. Pls answer asap. 3 decimal places.arrow_forward
- A circular footing having a diameter of 1.47m has its bottom at a depth of 2.54 m from the ground surface. The water table is located at a depth of 1.09m below the ground. FS = 2.86 Properties of soil are as follows: Specific gravity, GS = 2.72 Void ratio, e = 0.19 Cohesion, c=20.20 kPa, Assume local shear failure and Terzhagi's Bearing Capacity Equation. Use the following bearing capacity factors: Nc' = 11.85 Nq' = 3.88 Ny' = 1.12 Calculate the following Net Allowable load on the footing, kN HINT: Use Dry unit weight for soil above the groundwater table. Unit weight of water = 9.81 kN/m² NOTE: ROUND OFF ONLY ON THE FINAL ANSWERarrow_forwardA 2 m×4 m rectangular footing has to carry a uniformly distributed load of 120 kPa. As per the 2 :1 dispersion method of stress distribution, the increment in vertical stress (in kPa) at a depth of 2 m below the footing isarrow_forwardA 1.8 m square, 2 m deep and 1 m high footing supports a column load of 570 kN. It is supported on a clayey sand. There is no water present at the site. Use unit weight for the concrete 24 kN/m³. A dilatometer test run at the site has returned the following constrained modulus profile: Depth (m) M (MPa) 2 7.7 3 8.8 4 5 10.2 14.8 6 15.4 Plot the modulus distribution with depth considering both the strain distribution with depth and the soil moduli, and divide soil into 5 layers, then determine the average modulus for each soil layer.arrow_forward
- Principles of Geotechnical Engineering (MindTap C...Civil EngineeringISBN:9781305970939Author:Braja M. Das, Khaled SobhanPublisher:Cengage LearningFundamentals of Geotechnical Engineering (MindTap...Civil EngineeringISBN:9781305635180Author:Braja M. Das, Nagaratnam SivakuganPublisher:Cengage Learning