Soil bearing capacity tests

Apart from the abovementioned parameters, the resistance R value is also used. However, the resistance R value is indicative of performance when untreated or treated soil material is used. 

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The plate bearing test is used for the determination of soil bearing capacity with respect to the modulus of surface reaction (k value). The subgrade bearing capacity in terms of k value is used, mainly, in rigid pavement design methodologies. 

Direct shear tests are made in the laboratory to obtain data for determining the bearing capacity of soils and the stability of embankments. 

Standard geotechnical test reports address typical static properties of soil such as shear strength and bearing capacity but may not provide dynamic properties unless they are specifically requested. In these situations, it is necessary to use the static properties. Dynamic soil properties which are reported may be based on low strain amplitude tests which may or may not be applicable to the situation of interest. Soils reports will generally provide vertical and lateral stiffness values for the foundation type recommended. These can be used along with ultimate bearing capacities to perform a dynamic response calculation of the foundation for the applied blast load. 

Note that in Equation 5.15, unit weight is assumed to be equal to unit weight of pile. Because Nq is dependent on 0, a sample has to be obtained and tested for 0. For sand and granular soils, it is difficult to obtain their undisturbed samples. Because of this, an in situ test is usually performed to obtain 0. Two in situ test methods normally used are the standard penetration test (SPT) and cone penetration test (CPT). Some of these correlations have been presented earlier in this chapter. Figure 5.8 shows a plot of the bearing capacity factor, Nq. 

Similarly for a construction site, the nature or consistencies of the sub-surface soil strata would depend on the weathering profiles. In residual soils, for example, the soil strata would generally show increasing stiffness with depth, as evidenced by increasing Standard Penetration Test values with depth. Hence the deeper the soil stratum, the higher the bearing capacity and shear strength. 

Under no circumstances does the determination of group index exempt the engineer from not determining the bearing capacity of the soil material by other laboratory or in situ tests. 

The test determines the soil s bearing capacity from laboratory-compacted specimen, expressed as CBR. 

The suitability of the subgrade to provide the platform on which the pavement is to be constructed can be determined by classifying the material using any authorised soil classification system (ASTM D 2487 2011, AASHTO M 145 2012 or others). However, the determination of the bearing capacity or strength of the subgrade is obtained only after conducting laboratory or in situ tests. 

Mark C, Gemperline D, Hon Y. 1988. Centrifuge model tests for ultimate bearing capacity of footing son step slopes in cohesionless soils Centrifuge, 88 203-221. 

D1194-94 Standard Test Method for Bearing Capacity of Soil for Static Load and Spread Footings... 

Meyerhof, G. G. 1956. Penetration tests and bearing capacity of cohesionless sods, ASCE Journal of Soil Mechanics and Foundation Division, 82(1), 1-19. 

A foundation bearing pressure computation against which the second restart criterion can be tested is not available for SRS. A calculation performed by DOE staff determined that the maximum soil bearing pressure during an earthquake would be 8.24 ksf. The value is well below the design bearing capacity which has been shown to be in excess of 500 ksf. 

Equations 10.2 through 10.5 present the fundamental basis of any axial capacity determination, irrespective of the method to establish the soil parameters/and q. Several computation techniques are available to derive unit skin friction and unit end bearing either from laboratory and sampling data or from in-situ test data. The in-situ test most utilized is the cone penetration test (CPT). Details on the performance of the CPT can be found in Andresen et al. (1979) and de Ruiter (1971,1975). 

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