Allowable Bearing Pressure Research Articles

The Geotechnical Investigation of Subsoil Materials in a Typical Basement Terrain, Southwestern Nigeria- A Case study

Geotechnical investigation of the subsurface materials of a proposed Primary Health Center (PHC) in Modeke Oyo East Local Government Area (OELGA). of Oyo State has been conducted. The investigation is aimed to determine the suitability of the site for the proposed Bungalow building by assessing the subsoil strata that underlie the area. Three (3) points were tested to depth of 4.75m using a 2.5-ton DCPT equipment, while three (3) trial pits were dug to a depth of 1.5m with the aid of hand auger, and various lab analysis were conducted on selected samples from the trial pits. The result obtained from the DCPT indicates that subsurface is made up of stiff to very stiff sandy lateritic clay underlain by very stiff to hard sandy lateritic clay with hard pans layers. The allowable bearing pressure was observed to increase with depth to 4.75m further confirmed the subsurface lithologies. The Allowable Bearing Pressure (qa) in kN/m2) with a range of values 81 – 256 kN/m2, 54 – 155 kN/m2 and 162 – 338 kN/m2 for DCPT points 1, 2, and 3 respectively, indicate a Safe Bearing Pressure that can support load up to 45 kN/m with factor of safety of 2.5. Sieve analysis results revealed that the soil is well graded with dominant gravel which show a well-drained soil with good strength characteristics. Liquid limits ranged from 26.7% to 43.3%, plastic limits from 15% to 27% and plasticity index from 9.7% to 27.3%, thus indicating low to medium compressibility. The natural moisture contents values range between 4% and 15%, indicating lateritic clay of low to medium plasticity with low moisture content. Based on the above deductions, it can be concluded that, the factor of safety of 2.5 calculated from the allowable bearing pressure from the CPT, low to medium compressibility from Atterberg limits test and moisture content below 15% show that the investigated site is good and could safely support a bungalow building as proposed.

Allowable Bearing Capacity for Shallow Foundation in Eket Local Government Area, Akwa Ibom State, Southern Nigeria

P-wave and S-wave velocities were obtained from seismic refraction survey in the foundation layer of Eket, the study area. The Tezcan’s approach discussed extensively in the work was used in conjunction with the existing mathematical relations between elastic parameters and seismic refraction velocities for the study of foundation layers in the study area. Based on the results, the elastic constants, allowable bearing pressure/capacity, ultimate bearing capacity and other parameters in Table 1 were determined. The result shows that allowable bearing pressure increases with increase in shear modulus and shear wave velocity. The empirical relation between allowable bearing capacity and shear modulus shows that the allowable bearing capacity increases with depth. Comparing our findings with some ranges of safe allowable bearing capacities of similar non cohesive/granular soils in literatures, the second layer with allowable bearing capacity range of 72.56 - 206.63 kN·m-2 (average = 154.78 kN·m-2) has been considered to be the safe shallow engineering foundation in the study area. The empirical relations between allowable bearing capacities shear modulus and shear wave velocity, in conjunction with the inferred maps, which serve as our findings, will be used as guide in the location of foundations. The inferred ultimate and allowable capacities correlate maximally for the two shallow foundations penetrated by the seismic waves. This perfect correlation reflects the uniqueness of the method.

Allowable Bearing Pressure in Soils and Rocks through Seismic Wave Velocities

Based on a variety of case histories of site investigations, including extensive bore hole data, laboratory testing and geophysical prospecting at more than 550 construction sites, an empirical formulation is proposed for the rapid determination of allowable bearing pressure of shallow foundations in soils and rocks. The proposed expression corroborates consistently with the results of the classical theory and is proven to be rapid, and reliable. Plate load tests have been also carried out at three different sites, in order to further confirm the validity of the proposed method. It consists of only two soil parameters, namely, the in situ measured shear wave velocity and the unit weight. The unit weight may be also determined with sufficient accuracy, by means of other empirical expressions proposed, using P or S - wave velocities. It is indicated that once the shear and P-wave velocities are measured in situ by an appropriate geophysical survey, the allowable bearing pressure as well as the coefficient of subgrade reaction and many other elasticity parameters may be determined rapidly and reliably.

Allowable bearing pressure in soils and rocks through dynamic wave velocities

Based on a variety of case histories of site investigations, including extensive bore hole data, laboratory testing and geophysical prospecting at more than 550 construction sites, an empirical formulation is proposed for the rapid determination of allowable bearing pressure of shallow foundations. The proposed expression corroborates consistently with the results of the classical theory and is proven to be rapid and reliable. Plate load tests have also been carried out at three different sites to further confirm the validity of the proposed method. It consists of only two soil parameters, namely, the in situ measured shear wave velocity and the unit weight. The unit weight may also be determined with sufficient accuracy by means of another empirical expression proposed, using the P-wave velocity. It is indicated that once the shear and P-wave velocities are measured in situ by an appropriate geophysical survey, the allowable bearing pressure as well as the coefficient of subgrade reaction and many other elasticity parameters may be determined rapidly and reliably, not only for soils but also for rocks.

Allowable Bearing Pressures of Bridge Sills on GRS Abutments with Flexible Facing

Compared to geosynthetic-reinforced soil (GRS) retaining walls, GRS abutment walls are generally subjected to much greater intensity surface loads that are fairly close to the wall face. A major issue with the design of GRS abutments is the allowable bearing pressure of the bridge sill on the abutments. The allowable bearing pressure of a bridge sill over reinforced soil retaining walls has been limited to 200 kPa in the current NHI and Demo 82 design guidelines. A study was undertaken to investigate the allowable bearing pressures of bridge sills over GRS abutments with flexible facing. The study was conducted by the finite element method of analysis. The capability of the finite element computer code for analyzing the performance of GRS bridge abutments with modular block facing has been evaluated extensively prior to this study. A series of finite element analyses were carried out to examine the effect of sill type, sill width, soil stiffness/strength, reinforcement spacing, and foundation stiffness on the load-carrying capacity of GRS abutment sills. Based on the results of the analytical study, allowable bearing pressures of GRS abutments were determined based on two performance criteria: A limiting displacement criterion and a limiting shear strain criterion, as well as the writers' experiences with GRS walls and abutments. In addition, a recommended design procedure for determining the allowable bearing pressure is provided.

Allowable bearing pressure for shales and sandstones of the Kenny Hill formation : Toh, C T; Ting, W H; Ooi, T A Proc Ninth Southeast Asian Geotechnical Conference, Bangkok, 7–11 December 1987V2, P6.155–6.166. Publ Bangkok: Southeast Asian Geotechnical Society, 1987

Allowable bearing pressure for shales and sandstones of the Kenny Hill formation : Toh, C T; Ting, W H; Ooi, T A Proc Ninth Southeast Asian Geotechnical Conference, Bangkok, 7–11 December 1987V2, P6.155–6.166. Publ Bangkok: Southeast Asian Geotechnical Society, 1987

Rapid Selection of Column Base Plates

Over the past several years there have been a number of articles published proposing design aids for the rapid selection of column base plates. Although the design calculations as presented in the AISC Manual of Steel Construction, 7th Edition, are relatively simple, the selection of the optimum plate geometry cannot be determined directly and can be quite time consuming in a large steel structure. The previously presented design aids provided rapid solutions to the design problem, but sacrificed the accuracy of manual calculations. A graphical approach to the design will be presented in this paper, which provides rapid and accurate solutions to the design of steel bearing plates and can be expanded to cover all column sections and loading conditions. The design procedure recommended by the AISC assumes that the bearing pressure on the bottom of the plate is of uniform intensity and that the column load is uniformly distributed over an effective rectangular area equal to 0.95 times the depth of the column section by 0.80 times the column flange width. Thus, the required bearing area based on the relationship of column loading to allowable concrete bearing pressure is first determined and the plate geometry selected to satisfy this requirement. The plate thickness is then determined by treating that portion of the plate that projects beyond the "effective rectangle" as an inverted cantilever and solving for the required thickness.

Play between Bolt and Bolt Hole and Allowable Bearing Pressure.

Play between Bolt and Bolt Hole and Allowable Bearing Pressure.