Bearing Capacity Theory Research Articles

Field study of residual forces developed in pre-stressed high-strength concrete (PHC) pipe piles

A large-scale field testing program for the study of residual forces in pre-stressed high-strength concrete (PHC) pipe piles is presented in this paper. Five open-ended PHC pipe piles with 13 or 18 m in embedded length were installed and used for static loading tests at a building site in Hangzhou, China. All the piles were instrumented with fiber Bragg grating (FBG) strain gauges. The residual forces in these piles were recorded during and after installation. The measured load transfer data along a pile during the static loading tests are reported. The effect of the residual force on the interpretation of the load transfer behavior is discussed. The field data show that residual force along the installed pile increases approximately exponentially to the neutral plane and then reduces towards the toe. The residual force decreases with time to a stable value after pile jacking due to the secondary interaction between the pile and the disturbed soil around the pile and other factors. The large residual forces along the PHC pipe piles significantly affect the evaluation of the pile load distributions, and thus the shaft and toe resistances. The conventional bearing capacity theory tends to overestimate the shaft resistance at positions above the neutral plane and underestimate the shaft resistance at positions below the neutral plane, and the toe resistance for an open-ended PHC pipe piles founded in stratified soils.

Modeling and Experimental Validation of Penetration Lunar Surface Sampler for Future Food Production Projects

Sampling extraterrestrial soil, which reveals the composition and origination of celestial bodies, is one of the key technique in planet detecting. Penetrating soil with hollow cylinder is one simple, highly reliable and environmentally adaptable way to sample soil, but the sampling depth is limited by the penetration force of the sampling system. The penetration characteristics of the sampler are determined by the structural parameters and soil parameters. The study first presents a model to predict the inner wall friction in the frame of Janssen theory and continuum model hypothesis for future food production projects. The outer wall friction is then modeled according to the hypothesis that the soil outside the sampler is a semi-infinite body. The bearing force of the soil underneath the bottom of the sampler is calculated via the ground ultimate bearing capacity theory. The overall penetration force is the sum of the inner wall friction, outer wall friction and the bearing force. The consistency of the model predictions and experimental data is verified. The research in this study provides a theoretical basis for lunar surface sampling.

Estimating Bearing Capacity of Strip Footings over Two-Layered Sandy Soils Using the Characteristic Lines Method

A study on the bearing capacity of strip footings over sandy-layered soils has been conducted using the stress characteristic lines method. Traditional bearing capacity theories for specifying the ultimate bearing capacity of shallow foundations are based on the idea that the bearing layer is homogenous and infinite. In practice, layered soils are mainly being used. The stress characteristic lines method is a powerful numerical tool that can solve stability problems in geotechnical engineering. In the present paper, an appropriate algorithm is derived for estimating the static bearing capacity of strip footing located on two-layered soils using the stress characteristic lines method. Numerical and experimental examples are presented, to validate the proposed algorithm. Graphs and equations illustrate the effective depth of strip footings located on two-layered soils. If the friction angles of the top and bottom layers are 30° and 35°, respectively, the depth effect of the top layer is estimated to be 0.76 of the foundation’s width.

A prediction method for anchor penetration depth in clays

Anchoring is one of the main causes of subsea pipeline damage, which makes anchor penetration depth one of the most important references for the design of subsea pipeline burial depth. The anchor penetration process is analysed experimentally, numerically and theoretically. First, a series of model tests of dropping anchors are conducted to study the influences of anchor weight, dropping height on the penetration depth. Second, taking the effects of strain and strain rate into account, a finite element method (FEM) model of anchor penetration is set up with Coupled Eulerian–Lagrangian (CEL) method. The soil deformation and effects of strain and strain rate are analysed with the CEL model, and the model is validated against the test results. Then the effects of touch-down velocity and soil properties on penetration depth are analysed with the numerical model. Third, the anchor penetration process is analysed with classical bearing capacity theory. The average bearing coefficient during anchor penetration is back-analysed with experimental and numerical results. And a prediction method for the average bearing coefficient, which takes into account the effect of touch-down velocity, is proposed. Finally, the prediction process for the penetration depth of dropped anchor is proposed. The proposed method is of great significance for predicting anchor penetration depth and subsea pipeline burial depth.

Undrained capacity of surface foundations with zero-tension interface under planar V-H-M loading

Undrained capacity of strip and circular surface foundations with a zero-tension interface on a deposit with varying degrees of strength heterogeneity is investigated by finite element analyses. The method for simulating the zero-tension interface numerically is validated. Failure envelopes for strip and circular surface foundations under undrained planar V-H-M loading are presented and compared with predictions from traditional bearing capacity theory. Similar capacity is predicted with both methods in V-H and V-M loading space while the traditional bearing capacity approach under-estimates the V-H-M capacity derived from the numerical analyses due to superposition of solutions for load inclination and eccentricity not adequately capturing the true soil response. An approximating expression is proposed to describe the shape of normalised V-H-M failure envelopes for strip and circular foundations with a zero-tension interface. The unifying expression enables implementation in an automated calculation tool resulting in essentially instantaneous generation of combined loading failure envelopes and optimisation of a foundation design as a function of foundation size or material factor. In contrast, the traditional bearing capacity theory approach or direct numerical analyses for a given scenario requires ad-hoc analyses covering a range of input variables in order to obtain the ‘best’ design.

Residual Bearing Capacity Numerical Simulation and Theoretical Analysis of H-Shaped Steel Column Impacted under Different Axis Pressure

H-beam is usually used as column structure of single industrial workshop, steel column will inevitably encounter lateral impact of lifting weights or factory vehicle in the process of daily production, causing its defects in material and geometry, thus the change of axial bearing capacity.This aratical takes H-shaped steel column of a factory as the research object, establishes its residual bearing capacity theory of finite element analysis model in different situations under the impact using ABAQUS software platform, discusses the load parameters analysis in axial force-impac and Launches the functional relation between axial compression ratio and impact energy, providing a basis for assessing the residual loading capacity of such members after the impact.

Soil-buried pipeline interaction for vertical downwards relative offset

A new perspective is presented on the interaction effects for the vertical downwards offset of a pipeline relative to its surrounding soil. Instead of estimating the interaction force via shallow footing bearing capacity theory, as per common pipeline design practice, we assume that the vertical movement of the pipeline in uniform soil is governed by mechanisms similar to the lateral loading of a circular pile up to its limit load. The validity of this assumption is investigated numerically with the finite element limit analysis method, and design expressions are derived for the maximum interaction force on pipelines embedded in cohesive and granular soils. For the common case of buried pipelines built in sand-backfilled trenches, the same numerical method is employed to determine the necessary trench dimensions so as to avoid interaction with the possibly much stiffer native soil that results in a significant increase in the force applied on the pipeline during ground movement. The described approach can be employed in project-specific analyses to optimize trench dimensions, and thus avoid unnecessary excavation costs or mitigation measures.

Study on Flexural Performance of RC Beams Strengthened with Bonded Prestressed CFL

Based on experimental research and calculation theory of flexural bearing capacity, a method for calculating the ultimate load bearing of normal section member strengthened with prestressed CFL is proposed. Static load experimental results of two beams show that when prestress level is 20%, the cracking load and yield load of RC beams strengthened with prestressed CFL are 37.5% and 39.3% respectively. It is larger than that of RC beam strengthened with nonprestressed CFL.

Analytical Approach for Determination of Soil Shear Strength Parameters from CPT and CPTu Data

Shear strength parameters of soils C and $${\phi}$$ can be determined by means of laboratory tests and in situ testing data. Common approaches for determination of soil strength parameters from CPT data are on the basis of bearing capacity and cavity expansion theories. A new method is proposed for C, $${\phi}$$ prediction using all quantities, q c, u 2 and f s from CPTu considering bearing capacity mechanism of failure at cone tip and direct shear failure along the penetrometer sleeve. One advantage of this method is the improvement of accuracy in the case of erroneous data using all three outputs of CPTu. Laboratory test results, two sets of nonlinear equations by the proposed approach, and existing correlations of C and $${\phi}$$ angle parameters have been compared by applying them on a data base compiled from six sources. In current methods, cohesive parameters are not considered in bearing capacity equation and they cause the failure loads to be transferred to the second part of the basic bearing capacity equation which is a function of the internal friction angel. It has been considered that the internal friction angle obtained by current methods is relatively higher than the measured values. Also, the comparison of predicted and measured C and $${\phi}$$ angle values indicates good consistency and low scatter for the proposed method. Accordingly, this can lead to optimize design for geotechnical practice.

BEARING CAPACITY OF STRIP FOOTING USING KREY’S METHODS (FRICTION CIRCLE METHOD)

In geotechnical investigation, determination of the bearing capacity of foundation soil constitutes is an important task. Most of the previous studies investigated the stability of such foundation system using classical bearing theory. The classical bearing theory was developed depending on the theory of plasticity with the assumption that the soil behaves as a rigid-plastic material. The bearing capacity theories require making a guess on the shape and geometry of the most critical failure surface (mechanism of failure) a priori. Most theories assumed the geometry of the failing soil mass is symmetrical with respect to the center of the footing, while, Krey suggested that the geometry of the failing mass is unsymmetrical. Numerical methods do not require an initial assumption the geometry of the failure mode. In the present work, a numerical study assisted by a computer program is carried out using (Krey’s method) to investigate the center of the slip circle gives the minimum bearing capacity of the footing. Also, PLAXIS 2D used for analysis of some cases of studies by Krey’s method. Krey it's of the present study is compared with the classical theories of the ultimate bearing capacity. The predicted values of ultimate bearing capacity of soil of this study are less than those of others theories of ultimate bearing capacity. In order to facilitate the calculation of bearing capacity the proposed equations are used. It is a function of (footing width, (B), ratio of footing depth to its width, (Rf) , angle of internal friction of soil,

Research on Settlement and Bearing Capacity of Y-Section Pile Considering Abnormality Effect

The side friction of Y-section pile is non-uniform distributed along its inverted arch arc, the load - settlement law of Y-section pile distinguishes to the traditional piles' as there is abnormality effect of side friction. Computation theory of settlement and ultimate bearing capacity needs to be studied. Calculate the settlement under different loads based on the model of skin friction, ultimate tip resistance and additional stress coefficient, and then predict ultimate bearing capacity by loads-settlement laws, the theoretical values of settlement and ultimate bearing capacity are in good agreement with the results of Static load test. The influences of five variables R, θ, δ, s, and L on settlement of Y-section file are analyzed, the settlement of Y-section pile under the constant load decreases with the increase of R, δ, s, δ and increases with the increase of θ. The influences of Relevant parameters on ultimate bearing capacity are also analyzed, the ultimate bearing capacity of Y-section pile decreases with the increase of θ and increases with the increase of R, δ, s and L.

Ultimate Bearing Capacity Based on Unified Strength Theory

In the ultimate bearing capacity formulas, the factorNγhas not been given a definite expression, so the calculation diagrams are not serious and the hypothesis can’t match the reality. Most of the ultimate bearing capacity factors are received from the results of Prandtl theory, but the theoretic models they used are not the same. And most of the ultimate bearing capacity theories are based on Mohr-Coulomb theory, the effects of intermediate principle stress are ignored. To solve these problems, according to ultimate balance theory and unified strength theory, the analytical formulas of ultimate bearing capacity andNγare received when foundation is completely smooth. The results show that the ultimate bearing capacity will increase when considering the effects of intermediate principle stress and the formulas from practical experiences can make the ultimate bearing capacity unsteady.

Shape Effects on the Undrained Uplift Capacity of Skirted Suction Foundations in Clay

Skirted suction foundations are an attractive solution for floating offshore wind turbines that are subject to uplift due to overturning or buoyancy loading. Current industry design guidelines give conservative collapse loads for offshore shallow foundation systems, particularly due to neglecting the beneficial effect of suction developed within the soil plug during rapid uplift. The behavior of skirted rectangular and circular footings subjected to uplift loading has been studied using centrifuge model tests and upper bound plastic limit analyses. Results demonstrate that the shape effects on the uplift capacity factor are not significant when the circular and rectangular footings both obey reverse end bearing failure mechanism. Simple predictive methods based on existing bearing capacity theory are provided.

The Discussion about Improving the Bearing Capacity of Single Pile for Bored Pile in Sandy and Silt Layer

The bored pile which have the unique advantage in having no noise, no shake, no upheaval, no sides way in the process of construction has became into one of the most widely used pile foundations in high heavy construction in Inner Mongolia region. Through an engineering project of bored piles in Inner Mongolia region, this article takes an analysis for bearing behavior of the bored piles in sandy and silt layer in this region. It also discusses the influence construction technology on pile-end ultimate resistance and the reasonable range of reduction factor of the ultimate resistance. When the soil layers structure is similar, it could improve bearing capacity of single pile for bored pile by utilizing the supporting layer and substratums optional regrouping. Utilize traditional single pile bearing capacity theory formula calculating and the static load test results it takes an analysis, finding out the approach of improving the bearing capacity of single pile for bored pile in sandy and silt layer. So we could find the optimization design for pile foundation bearing capacity of bored pile and thus promote the improvement in bored piles theory research and engineering application level in Inner Mongolia region and provide theory and engineering design experience.

Model Calculation and Analysis of Geological Environmental Capacity in Qian'an Mining District

This paper puts forward environmental bearing capacity relative surplus rate and calculation model based on the theory of environmental bearing capacity, Through collecting and estimating the predictive value and ideal value of each index in different development stages and schemes, using analytic hierarchy process to established the target weight, environmental bearing capacity relative surplus rate of the rule layer and index level in Qian’an Mining area are calculated through the gradual convergence principle, accordingly the optimal solution to improve the environmental bearing capacity of Qian’an mining area is determined ,which provides scientific basis for promoting to realize the sustainable development of Qian’an Mining area.

Study of Factors with Effects on Tracked Vehicle Driving Resistance Basis of Bekker Theory

Tracked vehicle usually travels in soft ground, so the driving resistance is more complicated. In this paper, Terzaghi ground bearing capacity theory was analyzed. According to Baker pressure - settlement formula and retaining wall theory, compaction resistance and bulldozing resistance of the tracked vehicle were deduced basis of conservation of energy. Factors with effects on tracked vehicle driving resistance were analyzed by matlab simulation. The driving resistance variation was obtained. Theoretical support for tracked vehicle in soft ground running was provided.

Research on Numerical Simulation of High Filling Culverts Foundation Failure Mode

Foundation failure mode of high filling culverts involves calculation theory and method of subgrade bearing capacity, and it has great theoretical and practical values. After model of the culvert has been established, finite difference method will be used to do the numerical simulation in FLAC3D. Reaserch suggests that traditional Terzaghi/Meyerhof failure mode are not suitable for relatively deep buried subgrade of high filling culvert. Foundation failure of high filling culvert is caused by difference in stiffness and earth press, which result in settlement difference, and then forms subsidiary shear stress on the sliding surface. When stress value reaches shear strength of the foundation soil, shear failure occured.

Investigation of the vertical uplift capacity of deep water mudmats in clay

Subsea mudmats are used in deep water oil and gas fields to support seabed structures, such as pipelines, manifolds, and well heads. On soft soil, removing mudmats during maintenance or decommissioning may be difficult and costly due to the significant suction that develops at the mudmat–soil interface, considerably increasing the uplift resistance beyond the submerged self-weight of the mudmat. This paper describes a series of centrifuge tests performed to investigate the uplift resistance of plain mudmats resting on lightly overconsolidated clay. The model mudmat invert was instrumented with pore pressure transducers to monitor the suction developing at the mudmat invert at various uplift velocities, uplift eccentricities, and mudmat skirt lengths. The results show an increase in uplift resistance with pull-out velocity and the dominant role played by the uplift eccentricity in reducing suction at the mat invert. Simple predictive methods based on bearing capacity theory and combined loading interaction diagrams are provided.

Bearing Capacity of Shallow Foundation on Two Clay Layers by Numerical Approach

Natural soils are often deposited in layers. The estimation of the bearing capacity of the soil, using conventional bearing capacity theory based on the properties of the top layer, introduces significant inaccuracies if the thickness of the top layer is comparable to the width of the rigid footing placed on the soil surface. Saturated normally consolidated and lightly overconsolidated clays indicate that under undrained condition the cohesion of soil mass increases almost linearly with depth. A few theoretical studies have been proposed in the literature to incorporate the variation of cohesion with depth in the computation of the ultimate bearing capacity of strip and circular footings. In this paper, after reviewing previous works, numerical computations using the FLAC code (Fast Lagrangian Analyses of Continua) are reported to evaluate the two layered clays effect on the bearing capacity beneath rigid strip footing subject to axial static load. The results of the bearing capacity relating to the relative thickness of the top layer, the strength ratio of the soil two-layered clays and the rates of the increase of soil cohesion with depth are presented in Tables and graphs. The obtained results are compared with previous published results available in the literature.

Test Study on Size Effect of Flexural Performance of RC Free Beams

Experimental studies on size effect of flexural behavior of reinforced concrete beams are not carried out fully. Standard values are based on test results of small-size components, which are different from large-size components in practical engineering. For size effect on quasi-brittle materials such as concrete, related researches have been carried out for many years, but related test study combined with concrete structures or components are not sufficient. This article is based on experimental study of 13 reinforced concrete free beams, obtaining test data during different loading stage, such as carrying capacity, deflection, steel and concrete strain etc. Test results show that size effect of flexural behavior of RC free beams is mainly reflected in reinforcement yielding stage and concrete crushing stage. The negative size effect due to concrete material is not significant. Yet internal force arm and longitudinal reinforcement have a positive size effect on flexural behavior, strength and ductility reserves show a growing trend with specimen size increasing. The safety of calculation theory of bearing capacity in code is verified indirectly.