Introduction
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The main aim of this test is to get the value of parameters of shear strength without measuring the pressure of pore water.
Shear strength components are total stress, effective stress, and pressure of pore water.
The apparatus needed for the compilation of this test are given below in a listed manner-
The sample should be formed like a cylinder. The diameter of this cylinder should be equal to 38 millimeters. The ratio of height and diameter of this specimen should be two.
The internal diameter of the undisturbed soil sample is the same as the required internal diameter of the soil sample. Then it is extruded by a sample extruder and further it si pushed into the split mold. A trimmed knife is used then for trimming the ends of the specimen. Then it is taken out from the split mold.
The disturbed specimen is obtained by the compaction of the soil sample at the required water content and dry density in the big mold. This sample is then extracted by sampling tubes.
The procedures of the “uniaxial triaxial test” are given below in a step-by-step manner-
The data regarding soil parameters has been assumed in few cases where appropriate data are missing.
In this section a square column footing is designed. For designing square footing various aspects should be considered. As per Eurocode, the design of the foundation has been performed. Here some assumptions have been done for the calculation of the depth of foundation and size of the foundation.
The column is assumed to be axially loaded(Islam et al 2020). The size of the column is taken as 400mm x 400 mm. The “safe bearing capacity” of soil is considered 200 KN per meter square. There are two loads that are applied on the column footing. One is permanent load and another is variable load. The value of permanent load and variable loads are 1505 KN and 1100 KN respectively. Therefore the total load that is acting on the footing is (1505+1100) KN which is 2605 KN. C20 grade of concrete has been assumed here. Therefore the “compressive strength” of this concrete grade is 20 Newton per millimeter square. The steel grade has been chosen S450. Therefore the strength of steel members is 450 Newton per millimeter square.
The total load on the column (W) = 2605 KN = 2605 * 10^3 N
Footing’s self-weight = 10% of the column load = (2605 * 10^3) * 10% = 2605 * 10^2 N
Hence total load is = 2865500 N = 28655 * 10^2 N
Factored load is (W_{u}) = 42982 * 10^2 N
Ulitimate “bearing capacity” of soil is = 2 * 200 * 10^3 N/ m^2 = 400 * 10^3 N/m^2
Area of this footing =(4298200/400000) meter square = 10.76-meter square
Therefore one side of square footing is √10.76 meters that are 3.28meters.
Hence it is considered that the one side of this footing is 3.5 meters.
Therefore the size of the footing is 3.5m * 3.5m
P_{u} = ((1.5*W) / B^2)
In this above equation, B means the size of square footing
Here W is the value of load excluding 1.5 factors. The value of W is 2605*10^3 N
After putting all the values in the equation the ultimate upward pressure of soil is coming about 318979 N/ m^2
Bending moment about critical section,
B.M= P_{u}*B/8(B-b)^2
B.M= 318979* 3.5 / 8 (3.5-0.4)^2 N.mm = 1341107*10^3 N.mm
We know that, B.M = 0.138 f_{ck}b d^2
1341107*10^3= 0.138*20*3500*d^2
Or, d= 372.59 mm (Assume d= 500 mm)
Let the diameter of the single pile be d meters.
According to the analytical method,
Q_{up}= Q_{eb}+Q_{sf}
Here Q_{up }means the total load that is acting on the pile =16000 KN
It is assumed that the pile can resist the overall load by its end-bearing property(Dhatrak et al 2018). Therefore the resistance of skin friction can be considered as zero. All the resistance is given by the pile by its end surface area.
Hence for that, Q_{eb }should be calculated. The equation for the calculation of Q_{eb }is given below-
Q_{eb} = q_{b}* A_{b}
Here q_{b }is 9C, where C signifies the cohesion of the soil sample. Therefore the value of this factor is 900 KN per meter square
A_{b }can be calculated by π*r^2
Therefore 16000= 900*π*r^2
Or, r^2 = 5.6 m
or, r= 2.36 m
Hence the radius of the single pile is 2.36 m.
Therefore the diameter of this single pile is 4.72 Meters.
The length of the piles is 25 meters.
For bearing the loading total of 3 piles are required(Han et al 2019).
Total height is 5 m.
According to Rankin’s theory per length active force on the wall is= 0.5*K_{a}*γ*H^2
For Φ =24 degrees, the value of Ka is 0.428
Therefore the total active pressure on the surface of the wall is = (P1+P2+P3) KN
The value of P1, P2, and P3 are 3.27 KN,26.19KN, 59.26KN. Therefore the total load is 88.72 KN/m.
Let’s assume, the length of the base of this retaining wall is 3 m
Journals
Dhatrak, A.I., Ghawde, M. and Thakare, S.W., 2018. Experimental study on Belled Wedge Pile for different loadings in cohesionless soil. In Indian Geotechnical Conference, Indian Institute of Science Bengaluru (pp. 1-7).
Han, F., Salgado, R., Prezzi, M. and Lim, J., 2019. Axial resistance of nondisplacement pile groups in sand. Journal of Geotechnical and Geoenvironmental Engineering, 145(7), p.04019027.
Islam, M.N., 2020. Small Scale Experiments to Assess the Bearing Capacity of Footings on the Sloped Surface. Eng, 1(2), pp.240-248.
Ji, C., Zhang, J.F., Zhang, Q.H., Li, M.X. and Chen, T.Q., 2018. Experimental investigation of local scour around a new pile-group foundation for offshore wind turbines in bi-directional current. China Ocean Engineering, 32(6), pp.737-745.
Lee1a, S., Im2b, J., Cho2c, G.C. and Chang, I., 2019. Laboratory triaxial test behavior of xanthan gum biopolymer-treated sands.
Magade, S.B. and Ingle, R.K., 2019. Comparative study of moments with plate and solid elements for an isolated footing under axial load. In International conference on innovation in concrete for infrastructure challanges.
Mistry, H.K. and Lombardi, D., 2020. Role of SSI on seismic performance of nuclear reactors: A case study for a UK nuclear site. Nuclear Engineering and Design, 364, p.110691.
Olumuyiwa, O.F., 2020. Engineering Site Investigation and Shallow Foundation Design in Ore Area of Ondo State, Nigeria. Materials and Geoenvironment, 67(1), pp.21-33.
Vargas, R.R. and Zavala, G.J., 2019. Influence of the Variability of Geotechnical Parameters in Cantilever Retaining Walls Design. In Geotechnical Engineering in the XXI Century: Lessons learned and future challenges (pp. 1237-1244). IOS Press.
Wei, L., Xiao-Guang, J. and Zhong-Ya, Z., 2019. Triaxial test on concrete material containing accelerators under physical sulphate attack. Construction and Building Materials, 206, pp.641-654.
Wu, M., Wang, J., Russell, A. and Cheng, Z., 2021. DEM modelling of mini-triaxial test based on one-to-one mapping of sand particles. Géotechnique, 71(8), pp.714-727.
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