Foundation Load Research Articles

Study on upper limit solution and its application on bearing capacity of rock slope foundation

The determination and analysis of the bearing capacity of a slope foundation has become an important research topic in foundation design theory. To explore the ultimate bearing capacity of the rock foundation adjacent to a slope on the basis of the shear failure mode of a rock foundation on a semi-infinite plane, the failure mode of the rock foundation near the slope was established by analyzing the failure mechanism of the Bell solution. The upper limit theorem of limit analysis was used to build a velocity field allowable for maneuvering. Using this method, the ultimate bearing capacity of the Sandaozhuang open-pit mine was analyzed and calculated. The results show that the foundation load of the mine is less than the allowable bearing capacity; hence, the building on the slope meets the requirements of foundation bearing capacity. At the same time, this paper uses this method and existing research methods to compare and analyze this project with others, proving the rationality and feasibility of the proposed method. This paper further explores factors affecting the ultimate bearing capacity, such as the horizontal setback distance of the footing from the edge of the slope and the dip angle. It is concluded that the ultimate bearing capacity increases with increases in the distance to the slope and decreases in slope angle. The study also shows that the calculations developed and proposed in this paper for the bearing capacity of the rock foundation adjacent to the slope are reasonable and feasible, can be applied to the calculations of the bearing capacity of rock foundations near the slope, and have guiding significance for the project.

Influence of transmission tower load under extreme conditions during operation period on the stability of landslide and tower foundation

Taking Yanzi landslide and 500 kV transmission tower foundations on the landslide as the research object, this paper presents a study of the influence of transmission tower on the stability of landslide and tower foundation under extreme conditions during operation period. Firstly, the ultimate loads of transmission tower foundation under different operating conditions are determined. Secondly, based on the limit load of transmission tower, the overall and local stability of Yanzi landslide is analyzed. Finally, the disturbance of tower foundation load state on soil around the tower foundation and the change of tower foundation displacement are studied. The results show that, with the increase of wind speed, the tower foundation load In addition, under the action of wind load, the soil around the adjacent tower foundation basically does not affect each other, the maximum displacement of tower foundation does not exceed 0.5 mm, and the maximum inclination rate of tower foundation meets the requirements of cod.

Study on large tonnage pile foundation load test system and field test of long rock-socketed pile

Large tonnage pile foundation load test system is designed in this paper by using pre-stressed technique to optimize the design of anchor pile reaction beam system, in which project pile can be successfully taken as anchor pile. The test results show that the cracks and excessive deformations of the prestressed anti-force device designed in this study have not occurred, and the prestressed tendons of the anchor pile ensure that the anchor pile will not be pulled and fractured, and the prestressed tendons can be reused, thus ensuring the safety and reliability of the test. This test method can directly test bearing capacity of long rock-socketed piles, and analysis bearing behaviors from test results of sensors which embedded in the pile. Through test studied, authors summarized the vertical bearing characteristics of long rock-socketed piles and the main problems that should be paid attention to during design and construction, and provided reliable solutions.

Study on Soft Foundation Load of Right Line of Double Truss Tunnel

According to the load line structure example, the vertical support force of the initial support structure of the tunnel construction section is analyzed based on the load structure method. The calculation results and analysis show that the arch foundation load is scientific and effective. The calculation is for the control of the bearing capacity of the shallow-buried tunnel excavation foundation, and it has important engineering guiding significance to effectively prevent the large deformation of the tunnel section and the surface subsidence.

An exercise on the bearing capacity of strip foundations

This paper deals with the exact solution of the bearing capacity of strip foundations on weightless cohesive−frictional soil considering the inclination of the (a) foundation base, (b) ground surface and (c) loads on the foundation base and on the ground surface. It will be seen that the upper bound and the lower bound solutions coincide unless extreme conditions are considered. New definitions for the bearing capacity factors Nq and Nc will then be provided.

Settlement analysis of pile cap with normal and under-reamed piles

The use of pile foundations has become more popular in recent years, as the combined action of the pile cap and the piles can increase the bearing capacity, reduce settlement, and the piles can be arranged so as to reduce differential deflection in the pile cap. Piles are relatively long, slender members that transmit foundation loads through soil strata of low bearing capacity to deeper soil or rock strata having a high bearing capacity. In this study analysis of pile cap with considering different parameters like depth of the pile cap, width and breadth of the pile cap, type of piles and different types of soil which affect the behaviour of pile cap foundation is carried out by using Finite Element Software ANSYS. For understanding the settlement behaviour of pile cap foundation, parametric studies have been carried out in four types of clay by varying pile cap dimensions with two types of piles namely normal and under-reamed piles for different group of piles. Furthermore, the analysis results of settlement and stress values for the pile cap with normal and under-reamed piles are compared. From the study it can be concluded that settlement values of pile cap with under-reamed pile are less than the settlements of pile cap with normal pile. It means that the ultimate load bearing capacity of pile cap with under-reamed piles are greater than the pile cap with normal piles.

An analytical spectral stiffness method for buckling of rectangular plates on Winkler foundation subject to general boundary conditions

An analytical spectral stiffness method is proposed for the efficient and accurate buckling analysis of rectangular plates on Winkler foundation subject to general boundary conditions (BCs). The method combines the advantages of superposition method, stiffness-based method and the Wittrick–Williams algorithm. First, exact general solutions of the governing differential equation (GDE) of plate buckling considering both elastic foundation and biaxial loading is derived by using a modified Fourier series. The superposition of such general solutions satisfy the GDE exactly and BCs approximately, which guarantees the rapid convergence and high accuracy. Then, based on the exact general solution, the spectral stiffness matrix which relates the coefficients of plate generalized displacement BCs and force BCs is symbolically developed. As a result, arbitrary BCs can be prescribed straightforwardly in the stiffness-based model. As an efficient and reliable solution technique, the Wittrick–Williams algorithm with the J0 problem resolved is applied to obtain the critical buckling solutions. The accuracy and efficiency of the method are verified by comparing with other methods. Benchmark buckling solutions are provided for plates with all possible boundary conditions. Also, dependence of various factors such as foundation stiffness, load combinations and aspect ratio on the buckling behaviors are investigated.

Engineering Subsoil Characterization for Shallow Foundation Design in Ode Irele Area of Ondo State, Southwestern Nigeria

Integrated geophysical and geotechnical investigations for foundation design have proved to be good veritable tools in effective foundation design and construction. Geophysical and geotechnical methods involving electrical resistivity and cone penetration test have been carried out to investigate the foundation soil conditions of Ode Irele, southwestern Nigeria. Six vertical electrical sounding (VES) were carried out along two traverses; which is complemented by two cone penetration tests with seven trial tests at different subsurface depths. The geotechnical results showed that the soils are sand and silt dominated. All the tested parameters fall within the Nigeria federal ministry of works and housing specification with liquid limit (< 50%), plastic limit (< 30%), plasticity index (< 20%). The geoelectric sections identified maximum of six geoelectric/geologic subsurface layers comprising the topsoil (red sand), weathered layer (made up of coastal sand/white sand), clayey sand (which is the major aquitard in the area), intermediate sand aquifer unit. However the coastal sand layer has moderately high resistivity at shallow depth to sustain foundation load with thickness greater than 2 m. The groundwater level measured from existing borehole records 17.5 m which may not or seriously affect the bases of the foundation footing. Consequently an average allowable bearing capacity of 150 KN/m2 (ultimate bearing capacity of 450 KN/m2) would be appropriate for design of shallow foundation in the area, at a depth not less than 1.6 m in Ode Irele and 0.8 m at Ajagba. The foundation width of 0.6 m would produce minimum bearing settlement less than 25 mm. The appropriate (recommended) ultimate bearing and allowable bearing capacity for strip and square footings at depth levels of 0.6 – 1.2 m vary from 1486 – 1842 KN/m2 and 495 - 614 KN/m2; and 2056 – 2489 KN/m2 and 685 - 830 KN/m2 respectively.

Numerical analysis of single rammed aggregate piers installed in stratified soil profiles

In this study, Rammed Aggregate Pier systems are analyzed according to the numerical analysis that are performed by two dimensional commercial finite element analysis software. The focus point of the paper is to identify the effects of pier dimensions, stratification of foundation soil profile and load applying levels on the deformation behavior of interacted rammed aggregate pier-surrounding soil system at the installation stage. Interpretations of the parametrical analyses are focused on the deformation change via loading levels. The relative displacement occurrence between pier and soil matrix is also checked.

An optimization strategy for evaluating modified Cam clay parameters using self-boring pressuremeter test data

This paper presents an efficient, practical, and automated strategy for deriving modified Cam clay parameters from undrained self-boring pressuremeter (SBPM) data. A mixed approach involving a parametric sweep and numerical optimization is used, with a focus on parameter groups that dominate the modified Cam clay response in undrained cavity expansion. The proposed technique is illustrated using data from SBPM tests carried out in soft estuarine clay. The resulting parameters are used to back-analyse large-scale foundation load tests and are shown to provide an excellent match to the measured foundation response.

Mechanisms beneath rectangular shallow foundations on sands: vertical loading

This paper details analysis of deformation behaviour of silica and carbonate sands under a rectangular foundation subject to uniaxial vertical load based on results from a series of centrifuge model tests. A multiscale particle image velocimetry/digital image correlation (PIV/DIC) technique was used to record and analyse the foundation tests with high resolution and measurement precision. Cone penetrometer and pressuremeter tests provide in situ soil characterisation of the tested sand sample in the centrifuge environment. The soil behaviour is analysed through foundation load–settlement response and the observed soil deformation measurements. Different soil deformation mechanisms and strain behaviours were observed in the different sands tested, and the particle shape effect is considered, with data from scanning electron microscopy, to explain the differences. The results and analyses contribute towards better understanding of different soil behaviours under shallow foundations in different sands.

Prediction of ultimate bearing capacity of circular foundation on sand layer of limited thickness using artificial neural network

ABSTRACT The present study focuses on the development of an Artificial Neural Network (ANN) model equation to estimate the average ultimate load of shallow circular foundation on a sand layer of limited thickness underlain by a rigid rough base subjected to an eccentrically inclined load. The model is developed using the 260 number of data points obtained from extensive laboratory model tests. The input parameters considered are depth of embedment (Df /B) of the foundation, thickness of the sand layer to diameter of foundation ratio (H/B), eccentricity ratio (e/B), and load inclination to friction angle ratio (α/ϕ) to estimate the reduction factor RF as output. The RF is the ratio of the ultimate eccentrically inclined load on a sand layer of limited thickness to the ultimate eccentrically inclined load on a sand layer, which is extending to a great depth. Importance of input parameters, which reflect the output, is studied using Pearson’s correlation and Spearman’s rank correlation. The sensitivity analyses are carried out using Variable Perturbation methods and Weight methods. It has been professing that H/B ratio is the most important input parameter.

STUDY ON FAILURE MECHANISM OF STRIP FOUNDATION BUILDINGS CAUSED BY SURFACE HORIZONTAL DEFORMATION IN MINING AREA

The surface deformation caused by underground coal mining will cause great damage to the surface buildings. Especially for the strip foundation buildings, the surface horizontal deformation will cause the walls to crack and open, threatening the safe use of buildings. However, there is lacking research on the failure mechanism of strip foundation buildings caused by surface horizontal deformation. Therefore, it is particularly important to study the mechanism. In this paper, a mechanical model of additional stress distribution in the strip foundation under surface horizontal deformation is established. Based on the model, the internal stress variation characteristics of the longitudinal wall of strip foundation buildings are studied with different factors: friction coefficient, surface curvature, foundation load and foundation length under the surface horizontal deformation. The internal stress variation of the transverse wall of the strip foundation buildings is analysed. The theory is verified by numerical simulation and a case study from Fengfeng coalmine China. Finally, the protection methods of the strip foundation buildings under the surface horizontal deformation are proposed.

A simplified model for vibro compaction of granular soils

In many applications dealing with the foundation of structures on loose granular soils deep vibro compaction measures in the vibro flotation form are needed for the densification of the soil formation. An additional beneficial effect of this densification method is the increase of the resistance against liquefaction especially under seismic loading. One of the challenging questions refers to the size of the compaction grid points on ground surface in order to achieve a certain densification degree prior to the application of the foundation loads. In the majority of the known cases especially for the spacing between densification points empirical rules were applied based on the knowledge of the executing specialized company under similar site conditions. The empirical rules may in some cases be sufficient for the design but not always. In the present paper a method is outlined how the spacing of the densification points can be estimated using an analytical or a numerical approach in combination with the high cycle accumulation model (HCA) which is well known and can be used for a realistic estimation of the densification zone. The method can also be used in construction sites where the amplitude of vibration in the sandy soil can be measured in the vicinity of the rod vibrator and the HCA-model is used for the estimation of the densification intensity and area around the vibrating tube.

Intelligent Computing Based Formulas to Predict the Settlement of Shallow Foundations on Cohesionless Soils

Introduction:Although it is a regular duty of geotechnical engineers to evaluate how much shallow foundation settles in the granular soil, there is no well-approved formula for this task. The intent of this research is to develop a formula that is adequately simple to be used in routine geotechnical engineering work but complete enough to address the behavior of granular soil associated with the settlement issue.Methods:Cone penetration test and foundation load test data were used to generate a formula that can predict the settlement. Genetic Programming (GP) based Symbolic Regression (GP-SR) and artificial neural networks were used to develop an optimized formula. Settlements were also calculated using the finite method and compared to the results of the developed formula.Results and Conclusion:Two formulas were developed using SR, and several models were developed using ANN. ANN model 1 has the highest R2value (0.93) and the lowest MSE (0.16) among all developed ANN and GP-SR models. FEM settlements were almost double the measured ones in some instances.

Power Flow Management of the Grid-Connected Hybrid Renewable Energy System: A PLSANN Control Approach

This paper clarifies the optimal control strategy of Hybrid Renewable Energy System (HRES), which has the parallel execution of Lightning Search algorithm with Artificial Neural Network and Recurrent Neural Network (PLSANN). The projected system is composed of Photovoltaic (PV), Wind Turbine (WT), Fuel Cell (FC), and Battery, which can associate DC link and competent to balance the real and reactive power. The introduction of wind/PV power within an electric grid origin the PQ troubles are considered. At this point, the recompense policy of DC/DC converter is examined by PLSANN/RNN technique to provide the optimal power flow management of HRES. Here, LSA is exploited for the optimization process of real power and the Recurrent Neural Network (RNN) is utilized for the optimal reactive management. The projected process recognizes the finest control pulses of the DC/DC converter derived from the foundation part and load part limitation. The projected system is competent to establish the active power into the grid and additionally it is capable of enhancing the PQ. With proper control, HRES significantly enhance the dynamic security of the power system. The proposed method is implemented in MATLAB/Simulink working platform and analyzed their performances. The statistical analysis of proposed method is analyzed in terms of mean, median and standard deviation factors. In order to prove the effectiveness, the proposed method is compared with current techniques such as Combined Modified Bat Search algorithm–artificial neural network (CMBSNN) technique, Particle Swarm Optimization (PSO), Genetic Algorithm (GA) and PI controller.

Explicit Form of Exact Analytical Solution for Calculating Ground Displacement and Stress Induced by Shallow Tunneling and Its Application

In urban environment, it is often unavoidable for shallow tunnels to be constructed adjacent to existing pile foundations. To obtain the ground displacements and stresses induced by shallow tunneling and existing pile foundation loads, the key procedure involves superimposing the analytical solution for shallow tunneling in green‐field with the analytical solution for existing structure loads. In green‐field, the complex variable method provides exact analytical solutions of ground displacements and stresses caused by shallow tunneling. However, the exact analytical solutions are not directly expressed as explicit functions of the coordinates (x, y) in the physical plane (called implicit form of exact analytical solutions), whereas the displacements and stresses induced by existing structure loads are explicit functions of the coordinates (x, y) in the physical plane, which makes it difficult to superpose the displacements and stresses induced by existing structure loads. In this paper, explicit form of exact analytical solutions of displacements and stresses induced by shallow tunneling in green‐field is obtained by using the inverse conformal transformation and the Cauchy–Riemann equations. Comparison with implicit form of exact analytical solutions shows that the explicit form of exact analytical solutions is intuitional and easily used by engineers, and moreover, the calculation amount is much smaller than that for the implicit form of exact analytical solutions. Then, an application involving superimposing the explicit form of exact analytical solutions with Mindlin’s solution is implemented to analyze the secondary stress field and the related potential plastic zone caused by shallow tunneling adjacent to pile foundations. Moreover, the influences of pile foundation parameters on the ranges and shapes of the potential plastic zones induced by nearby tunneling are analyzed.

Evaluation of model uncertainties in reliability-based design of steel H-piles in axial compression

To account for uncertainties of load and resistance in a more rational way, reliability-based design (RBD) concepts have been increasingly applied to design bridge foundations. One of critical elements in the geotechnical RBD process is the characterization of model uncertainties. This paper compiles 126 and 23 reliable static load tests for steel H-piles in axial compression from two databases: Pile-Load Tests (PILOT) and Deep Foundation Load Test Database (DFLTD), respectively. The Davisson offset limit is adopted to define the measured resistance in clay, sand, and layered soil, which is verified with the L1–L2method developed for drilled shafts. A hyperbolic model with two parameters is chosen to fit the measured load–settlement curves. The uncertainties in resistance calculations and the load–settlement curves are captured by a ratio (or model factor) of measured to calculated resistance and the hyperbolic parameters. The mean values, coefficients of variation, and the probability distributions of the model factors are established from 149 load tests. The statistics of the resistance model factor are applied to calibrate the resistance factors (for the ultimate limit state) in load and resistance factor design of steel H-piles in axial compression. In future, the statistics of the hyperbolic parameters can be incorporated into the development of RBD of steel H-piles at the serviceability limit state.

Change of hydraulic conductivity of cohesive soils due to consolidation treatments with expanding resins

Settlements of ground subjected to foundation load are often due to both natural and/or anthropogenic causes, such as differential consolidation, seepage, periods of drought alternating with heavy rainfalls, growth of tree roots, sewer leaks, vibrations induced by vehicle traffic, excavations, or construction defects. Techniques of soil consolidation and stabilization by means of injection of polyurethane expanding resins have been efficiently used to mitigate or even solve this issue. The efficiency of the resin injection treatment has been well documented also thanks to the develop of a procedure of planning and monitoring which combines traditional geotechnical tests with the application of electrical resistivity tomography, which is strongly sensitive to the presence of water or voids. The combination of these survey methodologies allows to recognize the effect of injection in terms of soil compaction and water migration, a key factor for understanding the phenomenon and planning of resolutive interventions. The present study follows a previous work aimed at evaluating the increase in the geotechnical performance of cohesive soils treated by injection of expanding resins (same soil, resin, at the same site) and integrates it by focusing on the quantification of the effects of consolidation treatments, by means of expanding resins injection, on hydrologic properties of cohesive soils, focusing on saturated hydraulic conductivity measurements. Laboratory permeability test, performed in triaxial cell at different stress conditions and hydraulic gradients, were performed on undisturbed samples collected on “natural (non-treated)” and “treated soils”, before and after the injection of resin (MAXIMA ® by GEOSEC ® ) in a full-scale test site characterized by the presence of continuous and homogeneous cohesive soils, (clay and silts). The investigated soil is classified as CH or CL soil, very firm and apparently overconsolidated. The study shows how the treatment is able to modify the characteristics of hydraulic conductivity of the soil. The injected resins partly follow pre-existing weaknesses and partly impregnate homogeneous and continuous masses of soil in a capillary way, giving it, in addition to the already documented greater mechanical strength, a lower hydraulic conductivity. The electrical resistivity investigations allow to appreciate the volumes affected by the treatment to which the variations of the measured properties can be attributed.

Variation of loads on a three-bladed horizontal axis tidal turbine with frequency and blade position

Sustainable and cost effective design for tidal current turbines requires knowledge of the complex nature of unsteady loads on turbine components including blades, rotor and support structure. This study investigates experimentally the variation with frequency of rotor thrust and torque loads, of streamwise root bending moment on individual blades and of loads on foundation at the bed. Comparisons between these different load spectra are also established. The impact of absolute rotor angular position on blade and rotor thrust loads is also examined. The study is based on measurements from a 1/15 scale, three-bladed, horizontal axis machine tested in a recirculating flume, in onset flows of 3% and 12% turbulence intensity. It is found that for frequencies below the rotational frequency, load spectra are correlated to spectral density of the onset flow velocity. Above the rotational frequency, loads are mainly affected by turbine operation phenomena. The tower shadowing effect is clearly identified through frequency and angular analysis. Finally, thrust loads as experienced by the rotor alone are for the first time compared with streamwise and transverse foundation loads. Higher frequency loads experienced by the tower are shown to be affected by different vortex shedding regimes associated with different regions of the wake. All the experimental measurements presented in this article can be accessed from http://dx.doi.org/10.7488/ds/2423.