California Bearing Ratio Test on the Bearing Capacity of a Foundation in Unsaturated Soil

The value of the California bearing ratio (CBR) test is an index making it possible to evaluate the load of the foundation soil and the resistance of the pavement materials. The California Bearing Ratio (CBR) of unsaturated soils is particularly related to their quality. The mechanism affecting the bearing capacity, in the case of California Bearing Ratio (CBR), has been studied as a transformation of red clay for the backfill. In this study, the effect of compaction energy on compaction characteristics and California Bearing Ratio (CBR) values was investigated. The relationship between the CBR value (California Ratio Ratio) and the degree of compaction is characterized by a gradual evolution of unsaturated soils with different water contents. The results show that the compaction degree and California Bearing Ratio (CBR) value of the soil in the cold region are insufficient, but the bearing capacity of the compacted soil after immersion under the maximum dry density can still meet the filling requirements. The red clays tested are considered useful as bedding in areas of unsaturated soils.

Influence of Incomplete Soil Plugs on Bearing Capacities of Bucket Foundations in Clay

Due to the uneven seabed and heaving of soil during pumping,incomplete soil plugs may occur during the installation of bucket foundations,and the impacts on the bearing capacities of bucket foundations need to be evaluated.In this paper,the contact ratio(the ratio of the top diameter of the soil plug to the diameter of the bucket)and the soil plug ratio(the ratio of the soil heave height to the skirt height)are defined to describe the shape and size of the incomplete soil plug.Then,finite element models are established to investigate the bearing capacities of bucket foundations with incomplete soil plugs and the influences of the contact ratios,and the soil plug ratios on the bearing capacities are analyzed.The results show that the vertical bearing capacity of bucket foundations in homogeneous soil continuously improves with the increase of the contact ratio.However,in normally consolidated soil,the vertical bearing capacity barely changes when the contact ratio is smaller than 0.75,while the bearing capacity suddenly increases when the contact ratio increases to 1 due to the change of failure mode.The contact ratio hardly affects the horizontal bearing capacity of bucket foundations.Moreover,the moment bearing capacity improves with the increase of the contact ratio for small aspect ratios,but hardly varies with increasing contact ratio for aspect ratios larger than 0.5.Consequently,the reduction coefficient method is proposed based on this analysis to calculate the bearing capacities of bucket foundations considering the influence of incomplete soil plugs.The comparison results show that the proposed reduction coefficient method can be used to evaluate the influences of incomplete soil plug on the bearing capacities of bucket foundations.

Upper Bound Solution of the Resisting Moment Bearing Capacity of A Composite Bucket Shallow Foundation of An Offshore Wind Turbine in Sand

Bearing the large moment that is generated by the wind load that acts on the upper structure of offshore wind turbines is an important feature of their foundations that is different from other offshore structures.A composite bucket shallow foundation(CBSF)has been proposed by Tianjin University to address the soft geological conditions in the offshore regions of China for wind turbines.The CBSF is a new type of foundation and is effective against large moments.The soil deformation test of a CBSF and the numerical simulation study under the same working conditions are carried out to determine the failure mechanism of a CBSF under moment loading.The resisting soil compression rateηm is defined as a new empirical parameter that indicates the ability of the soil inside the bucket to resist moment loading.The upper limit of the resisting moment bearing capacity of the bucket foundation is derived through the upper bound theorem of classical plasticity theory based on the failure mechanism.The calculation method is validated by tests of bucket models with different height-diameter ratios in sand under moment loading.

Study of the Hole Wall Soil's Capacity by the Action of the Bearing Device of Rodless Drilling Rig

In order to ensure the bearing device of rodless drilling rig to press stably against the hole wall, it has to analyze the contact between the soil pore wall and the bearing device to study whether the soil pore will shear failure. This paper uses the method to calculate the additional stress of any point in soil mechanics to get the three-dimensional stress state of any point of the soil pore under the support plate, and use the numerical analysis method to calculate the shear stress and its relative intensity. Under the circumstances of maximum torque and maximum pressure, ABAQUS is used to make a finite element analysis of the capacity of the soil pore. The results of numerical analysis and FEA indicate that in the condition of the support plate will not deform; the contact area between the soil pore and the support plate is rectangular; in the force process, the soil under the ends of the support plate have the trend of yield, while it meets the condition of Mohr-Coulomb not to yield generally.

Methods for Estimating the Ultimate Bearing Capacity of Layered Foundations

The Meyerhof and Hanna′s(M-H) method to estimate the ultimate bearing capacity of layered foundations was improved. The experimental results of the load tests in Tianjin New Harbor were compared with predictions with the method recommended by the code for the foundations of harbor engineering, i.e. Hansen′s method and the improved M-H method. The results of the comparisons implied that the code and the improved M-H method could give a better prediction.

Correlation between the Bearing Capacity of Crude Oil Contaminated Soil of Mgbede and the Percentage Contamination

This study was conducted in Mgbede, River State, Nigeria, hosting up to, or even more than 100 oil wells. It examined the relationship between the bearing capacity of crude oil contaminated soil and the percentage contamination. Four uncontaminated soil samples were randomly collected at 1.5 m depth within the oil field with hand auger and analyzed for the load bearing properties limited to cohesion, angle of internal friction and bulk density. With these parameters, the bearing capacity was determined for each sample. Crude oil, collected from one of the oil wells with viscosity 0.02611 poises at 40~C and specific gravity 0.8227 g/cm3, was used as the contaminant. This was mixed with the soil sample at 5%, 10%, 15% and 20% concentrations. The mean values of the bearing capacity were 582.458 KN/m2, 495.35 KN/m2 for square and strip footings respectively at 0% contamination, 240.735 KN/m2 and 204.753 KN/m2 at 5%, 321.683 KN/m2 and 274.593 KN/m2 at 10%, 127.003 KN/m2 and 109.12 KN/m2 at 15%, 105.28 KN/m2 and 90.758 KN/m2 at 20% for square and strip footings, respectively. The results showed a consistent decrease in the load bearing values as the crude oil content increased. The result of the null hypothesis established a strong and significant relationship between the bearing capacity of crude oil contaminated soil and the percentage contamination.

Integration of GIS with the Generalized Reciprocal Method(GRM)for Determining Foundation Bearing Capacity:A Case Study in Opolo,Yenagoa Bayelsa State,Nigeria

This study addresses the pressing need to assess foundation bearing capacity in Opolo,Yenagoa,Bayelsa State,Nigeria.The significance lies in the dearth of comprehensive geotechnical data for construction planning in the region.Past research is limited and this study contributes valuable insights by integrating Geographic Information System(GIS)with the Generalized Reciprocal Method(GRM).To collect data,near-surface seismic refraction surveys were conducted along three designated lines,utilizing ABEM Terraloc Mark 6 equipment,Easy Refract,and ArcGIS 10.4.1 software.This methodology allowed for the determination of key geotechnical parameters essential for soil characterization at potential foundation sites.The results revealed three distinct geoseismic layers.The uppermost layer,within a depth of 0.89 to 1.50 meters,exhibited inadequate compressional and shear wave velocities and low values for oedometric modulus,shear modulus,N-value,ultimate bearing capacity,and allowable bearing capacity.This indicates the presence of unsuitable,soft,and weak alluvial deposits for substantial structural loads.In contrast,the second layer(1.52 to 3.84 m depth)displayed favorable geotechnical parameters,making it suitable for various construction loads.The third layer(15.00 to 26.05 m depth)exhibited varying characteristics.The GIS analysis highlighted the unsuitability of the uppermost layer for construction,while the second and third layers were found to be fairly competent and suitable for shallow footing and foundation design.In summary,this study highlights the importance of geotechnical surveys in Opolo’s construction planning.It offers vital information for informed choices,addresses issues in the initial layer,and suggests secure,sustainable construction options.

Undrained Capacity of a Bucket Foundation with a Limited-Tension Interface for Offshore Wind Turbines

In this paper,the influence of the limited-tension interface between lid and soil on the undrained bearing capacity of the wide-shallow bucket foundation is examined by finite element(FE)analysis.The interface between the lid and the soil is modeled using a simplified approach called the surface-based cohesive behavior,with the aim of simulating the limited-tension interface.Initially,the interaction between the lid and the soil is explored under the zero-and unlimited-tension conditions by small-scale experiments.Afterward,the effects of the embedment ratio,soil strength heterogeneity,and lid-soil interface on the bearing capacity are outlined,and the failure mechanisms are explained by FE analysis.A modified closed-form formula is given to compute the moment bearing capacity with the limited-tension interface between the lid and the soil for different embedment ratios and soil strength heterogeneities.The numerical results reveal that the existing approximating solutions,which assume fully bonded interaction,accurately exhibit the shape of the normalized failure envelopes in hm and vh load space for the limited-tension interface.However,the shape of the vm envelopes differs,requiring a novel solution to estimate the combined bearing capacity of the bucket foundation based on the embedment ratio and soil strength heterogeneity with a zero-tension interface between the lid and the soil.

Estimation of Undrained Bearing Capacity for Offshore Soft Foundations with Cyclic Load

The degradation strength of soils under cyclic loading is studied and a method for determining the cyclic degradation strength with cyclic triaxial tests is given in the paper. Furthermore, a dum my static method for estimating the undrained bearing capacity for offshore soft foundation under wave loads is developed. It can consider the effect of the difference of cyclic stress for different parts of the foundation on both the degradation strength of the foundation soil and the bearing capacity so that the estimated result can better reflect the real condition of foundation under cyclic loading. The method can be applied to plane and space problem.

Bearing Capacity and Technical Advantages of Composite Bucket Foundation of Offshore Wind Turbines

Based on mechanical characteristics such as large vertical load, large horizontal load, large bending moment and complex geological conditions, a large scale composite bucket foundation （CBF） is put forward. Both the theoretical analysis and numerical simulation are employed to study the bearing capacity of CBF and the relationship between loads and ground deformation. Furthermore, monopile, high-rise pile cap, tripod and CBF designs are compared to analyze the bearing capacity and ground deformation, with a 3-MW wind generator as an example. The resuits indicate that CBF can effectively bear horizontal load and large bending moment resulting from upper structures and environmental load.

Empirical methods for determining shaft bearing capacity of semi-deep foundations socketed in rocks

Semi-deep foundations socketed in rocks are considered to be a viable option for the foundations in the presence of heavy load imposed by high-rise structures, due to the low settlement and high bearing capacity. In the optimum design of semi-deep foundations, prediction of the shaft bearing capacity, rs, of foundations socketed in rocks is thus critically important. In this study, the unconfined compressive strength(UCS), qu, has been applied in order to investigate the shaft bearing capacity. For this, a database of 106 full-scale load tests is compiled with UCS values of surrounding rocks, in which 34 tests with rock quality designation(RQD), and 5 tests with rock mass rating(RMR). The bearing rocks for semi-deep foundations include limestone, mudstone, siltstone, shale, granite, tuff, granodiorite, claystone, sandstone, phyllite, schist, and greywacke. Using the database, the applicability and accuracy of the existing empirical methods are evaluated and new relations are derived between the shaft bearing capacity and UCS based on the types of rocks. Moreover, a general equation in case of unknown rock types is proposed and it is verified by another set of data. Since rock-socketed shafts are supported by rock mass(not intact rock), a reduction factor for the compressive strength is suggested and verified in which the effect of discontinuities is considered using the modified UCS, qu(modified), based upon RMR and RQD in order to take into account the effect of the rock mass properties.

Bearing capacity of foundation on slope determined by energy dissipation method and model experiments

To determine the ultimate bearing capacity of foundations on sloping ground surface in practice, energy dissipation method was used to formulate the beating capacity as programming problem, and full-scale model experiments were investigated to analyze the performance of the soil slopes loaded by a strip footing in laboratory. The soil failure is governed by a linear Mohr-Coulomb yield criterion, and soil deformation follows an associated flow rule. Based on the energy dissipation method of plastic mechanics, a multi-wedge translational failure mechanism was employed to obtain the three bearing capacity factors related to cohesion, equivalent surcharge load and the unit gravity for various slope inclination angles. Numerical results were compared with those of the published solutions using finite element method and those of model experiments. The bearing capacity factors were presented in the form of design charts for practical use in engineering. The results show that limit analysis solutions approximate to those of model tests, and that the energy dissipation method is effective to estimate bearing capacity of soil slope.

Lateral Bearing Capacity of Multi-Bucket Foundation in Soft Ground

The bucket foundation is a new type of foundation for offshore application to intermediate-depth waters. It has advantages over conventional ones. However, there is no consensus in the analysis and design of this type of foundation. In this paper, the lateral bearing capacity and the failure mechanism of multi-bucket foundations are studied with different connection stiffness and bucket spacing by use of a three-dimensional finite element method. Based on the numerical analysis results, a limit analysis method of plasticity for evaluating the lateral bearing capacity of large-spacing multi- bucket foundation with rigid connection in soft ground is proposed. This method provides a simple procedure that gives results comparable to those from the finite element analyses.

Probabilistic analysis of ultimate seismic bearing capacity of strip foundations

This paper presents a reliability analysis of the pseudo-static seismic bearing capacity of a strip foundation using the limit equilibrium theory. The first-order reliability method(FORM) is employed to calculate the reliability index. The response surface methodology(RSM) is used to assess the Hasofer e Lind reliability index and then it is optimized using a genetic algorithm(GA). The random variables used are the soil shear strength parameters and the seismic coefficients(khand kv). Two assumptions(normal and non-normal distribution) are used for the random variables. The assumption of uncorrelated variables was found to be conservative in comparison to that of negatively correlated soil shear strength parameters. The assumption of non-normal distribution for the random variables can induce a negative effect on the reliability index of the practical range of the seismic bearing capacity.

Seismic stability of reinforced soil walls under bearing capacity failure by pseudo-dynamic method

In order to evaluate the seismic stability of reinforced soil walls against bearing capacity failure,the seismic safety factor of reinforced soil walls was determined by using pseudo-dynamic method,and calculated by considering different parameters,such as horizontal and vertical seismic acceleration coefficients,ratio of reinforcement length to wall height,back fill friction angle,foundation soil friction angle,soil reinforcement interface friction angle and surcharge.The parametric study shows that the seismic safety factor increases by 24-fold when the foundation soil friction angle varies from 25°to 45°,and increases by 2-fold when the soil reinforcement interface friction angle varies from 0 to 30°.That is to say,the bigger values the foundation soil and/or soil reinforcement interface friction angles have,the safer the reinforced soil walls become in the seismic design.The results were also compared with those obtained from pseudo-static method.It is found that there is a higher value of the safety factor by the present work.

Characteristic Test Study on Bearing Capacity of Suction Caisson Foundation Under Vertical Load

Suction caisson foundations are often subjected to vertical uplift loads,but there are still no wide and spread engineering specifications on design and calculation method for uplift bearing capacity of suction caisson foundation.So it is important to establish an uplift failure criterion.In order to study the uplift bearing mechanism and failure mode of suction caisson foundation,a series of model tests were carried out considering the effects of aspect ratio,soil permeability and loading mode.Test results indicate that the residual negative pressure at the top of caisson is beneficial to enhance uplift bearing capacity.The smaller the permeability coefficient is,the higher the residual negative pressure will be.And the residual negative pressure is approximately equal to the water head that causes seepage in the caisson.When the load reaches the ultimate bearing capacity,both the top and bottom negative pressures are smaller than Su and both the top and bottom reverse bearing capacity factors are smaller than 1.0 in soft clay.Combined the uplift bearing characteristics of caisson in sandy soil and soft clay,the bearing capacity composition and the calculation method are proposed.It can provide a reference for the engineering design of suction caisson foundation under vertical load.

Construction of improved rigid blocks failure mechanism for ultimate bearing capacity calculation based on slip-line field theory

Based on the slip-line field theory, a two-dimensional slip failure mechanism with mesh-like rigid block system was constructed to analyze the ultimate bearing capacity problems of rough foundation within the framework of the upper bound limit analysis theorem. In the velocity discontinuities in transition area, the velocity changes in radial and tangent directions are allowed. The objective functions of the stability problems of geotechnical structures are obtained by equating the work rate of external force to internal dissipation along the velocity discontinuities, and then the objective functions are transformed as an upper-bound mathematic optimization model. The upper bound solutions for the objective functions are obtained by use of the nonlinear sequential quadratic programming and interior point method. From the numerical results and comparative analysis, it can be seen that the method presented in this work gives better calculation results than existing upper bound methods and can be used to establish the more accurate plastic collapse load for the ultimate bearing capacity of rough foundation.

New design equations for estimation of ultimate bearing capacity of shallow foundations resting on rock masses

Rock masses are commonly used as the underlying layer of important structures such as bridges, dams and transportation constructions. The success of a foundation design for such structures mainly depends on the accuracy of estimating the bearing capacity of rock beneath them. Several traditional numerical approaches are proposed for the estimation of the bearing capacity of foundations resting on rock masses to avoid performing elaborate and expensive experimental studies. Despite this fact, there still exists a serious need to develop more robust predictive models. This paper proposes new nonlinear prediction models for the ultimate bearing capacity of shallow foundations resting on non-fractured rock masses using a novel evolutionary computational approach, called linear genetic programming. A comprehensive set of rock socket, centrifuge rock socket, plate load and large-scaled footing load test results is used to develop the models. In order to verify the validity of the models, the sensitivity analysis is conducted and discussed. The results indicate that the proposed models accurately characterize the bearing capacity of shallow foundations. The correlation coefficients between the experimental and predicted bearing capacity values are equal to 0.95 and 0.96 for the best LGP models. Moreover, the derived models reach a notably better prediction performance than the traditional equations.

Finite element analysis of effect of soil displacement on bearing capacity of single friction pile

Effect of soil displacement on friction single pile in the cases of tunneling,surcharge load and uniform soil movement was discussed in details with finite element method.Lateral displacement of the pile caused by soil displacement reached about 90% of the total displacement,which means that P-Δ effect of axial load can be neglected.The maximum moment of pile decreased from 159 kN·m to 133 kN·m in the case of surcharge load when the axial load increased from 0 to the ultimate load.When deformation of pile caused by soil displacement is large,axial load applied on pile-head plays the role of reducing the maximum bending moment in concrete pile to some extent.When pile is on one side of the tunnel,soil displacements around the pile are all alike,which means that the soil pressures around the pile do not decrease during tunneling.Therefore,Q-s curve of the pile affected by tunneling is very close to that of pile in static loading test.Bearing capacities of piles influenced by surcharge load and uniform soil movement are 2480 kN and 2630 kN,respectively,which are a little greater than that of the pile in static loading test(2400 kN).Soil pressures along pile increase due to surcharge load and uniform soil movement,and so do the shaft resistances along pile,as a result,when rebars in concrete piles are enough,bearing capacity of pile affected by soil displacement increases compared with that of pile in static loading test.

Effect of Bearing Capacity on Designing Foundations in Iraq Using STAAD Pro-v8i

Most of Iraqi soil is classified as Quaternary deposits, especially in the Mesopotamian plain and tributaries of the River Tigris. Soil varies from north to south of Iraq. These differences in soil affected the process to select the suitable type of foundation. This research is to study the effect of bearing capacity on shallow foundations in different regions of Iraq. Seventy nine samples were collected from 23 boreholes at three different locations (Mosul at the North, Baghdad at the middle and Basrah at the south of Iraq). The samples were collected at varying depth between 1 to 24 m. They were subjected to the following testes: Atterberg limits, sieve and hydrometers, consolidation, direct shear, unconfined compression and the filed (SPT test). The values of the bearing capacity parameters ( and c) were obtained from the above tests. The results obtained were used in the application of the general equation of the bearing capacity. Then, the model of a building was designed (two floors, with mat foundation type) using STAAD Pro software. The average values of bearing capacity in each region were applied in the program (Mosul = 177 KPa, Baghdad = 125 KPa and Basrah = 84 KPa). In addition, the worst bearing capacity values were also used for the three regions (Mosul = 77 KPa, Baghdad = 68 KPa and Basrah = 24 KPa). The results obtained from the average and worst bearing capacity indicated that for Mosul, we could use shallow foundation (spread and mat used if there was basement) for different areas and for buildings with many stories. For Baghdad region, shallow foundation was more suitable for building not higher than five stories. Finally, for Basrah region, shallow foundations were an appropriate selection, but for most areas deep foundation was the right choice.