Stability Analysis Of Foundations Research Articles

The Bearing Capacity Analysis of Deep Foundation based on In-situ Dynamic Penetration Test Compared to Pile Driving Analyzer (PDA)

On road/ bridge construction, foundation stability analysis is carried out by reviewing the bearing capacity. At the planning stage, this aspect can be calculated based on empirical and numerical methods using In-situ Dynamic Penetration Test data. Meanwhile, at the implementation stage, the bearing capacity results are checked using Pile Driving Analyzer (PDA). Hereinafter, the bearing capacity result in the field is compared with the bearing capacity result at the planning stage whether they are appropriate or not. In this study, the results of bearing capacity based on empirical using Meyerhoff and Schmertmann and numerical methods using MIDAS GTS NX were compared with the results of the PDA test. This study takes an overview of the Semarang – Demak Toll Road Development Project Package 2 STA 16 + 075. The analysis was carried out based on three STA points. The results obtained show that the largest deviation value is when the PDA result is compared with the Schmertmann method, which is 0.59 and the smallest deviation is when comparing PDA with MIDAS 0.03. Both deviations are located on P 133F STA 16+711. This different deviation is due to the ultimate bearing capacity analysis based on empirical equations that only analyze single piles based on the original soil properties, while the MIDAS analysis also considers pile parameters and interface parameters. Moreover, in the PDA test, there are factors of environmental conditions.

System reliability analysis of foundation stability of gravity dams considering anisotropic seepage and multiple sliding surfaces

PurposeFor gravity dams built on foundations with directional joint sets, the seepage in the foundation possesses anisotropic characteristics and may have adverse effects on the foundation stability. A methodology for system reliability analysis of gravity dam foundations considering anisotropic seepage and multiple sliding surfaces is proposed in this paper.Design/methodology/approachAnisotropic seepages in dam foundations are simulated using finite element method (FEM) with the equivalent continuum model (ECM), and their effect on dam foundation stability is involved by uplift pressures acting on the potential sliding surfaces. The system failure probability of the dam foundation is efficiently estimated using Monte Carlo method (MCM) combined with response surface method (RSM).FindingsThe case study shows that it is necessary to consider the possibly adverse effect of anisotropic seepage on foundation stability of gravity dams and the deterministic analysis of the foundation stability may be misleading. The system reliability analysis of the dam foundation is justified, as the uncertainties in shear strength parameters of the foundation rocks and joint sets as well as aperture, connectivity and spacing of the joint sets are quantified and the system effect of the multiple potential sliding surfaces on the foundation reliability is reasonably considered.Originality/value(1) A methodology is proposed for efficient system reliability analysis of foundation stability of gravity dams considering anisotropic seepage and multiple sliding surfaces (2) The influence of anisotropic seepage on the stability of gravity dam foundation is revealed (3) The influence of estimation errors of RSMs on the system reliability assessment of dam foundation is investigated.

A review on stability of polyhouse structures

Naturally ventilated polyhouse is popular all over the world for growing high value cropssuch as capsicum, tomato, lettuce, herbs etc. and these polyhouses are available in different designs as per different climatic conditions. Structure failure is the major problem faced by farmers throughout the world. The several studies carried out throughout the world shows that the single design of polyhouse cannot be adopted throughout the country due to different agro-climatic conditions.As per differentstudies, polyhousestability designs are analyzed for dead load, live load, snow load, wind load and load combination and Loads were calculated by adoptingdifferent National Standards. Moreover, Truss members, columns and foundation stability analysis is carried out by considering dead loads, live loads and wind loads in most of the studies. Support reactions arealso calculated on truss joints and column joints. The optimum design of any polyhouse generally depends on its structural design, specific mechanical and physical properties of the individual structural components i.e., foundation, hoops, lateral support, polygrip, assembly and end frame. From all the studies it is reported that in most parts of the world, wind is the major force responsible for the failure of any polyhouse structure.

Frost-Heave Deformation and Prevention Technology of Power Transmission and Transformation Foundation under Extreme Boundary Temperature

Freezing and thawing disasters in seasonal frozen soil areas seriously affect the safety of power transmission and transformation projects. Studying the distribution of soil temperature and deformation under thermal insulation foundations is an important basis for the analysis of foundation stability in seasonal frozen soil areas. The thermal protection structure is closely related to the thickness of the insulation layer and the external thermal field. This dissertation takes the typical tower foundation of the 750 kV Hexi Power Grid Project and the geological conditions of the Shule River area in Gansu as the research objects. The theoretical analysis and numerical simulation methods are used to consider the impact of different thermal protection structures on the tower foundation and surrounding soil under extreme boundary temperatures. The influence of body deformation, stress, and temperature changes was analyzed. Through comparative analysis, it is found that the optimized structural form can effectively increase the temperature of the soil in extreme environments, avoid frost heave, and meet the design requirements for bearing capacity. In addition, the thermal-mechanical coupling analysis of the foundations of the initial temperature fields of different boundaries is carried out, and the applicability of the insulation foundation under different boundary conditions is discussed.

Verification of a DDA-based hydro-mechanical model and its application to dam foundation stability analysis

There are many studies concerning hydro-mechanical coupling model based on discontinuous deformation analysis (DDA). However, verification of the coupling model and its application to practical engineering are rarely found. In this paper, we first introduced the distributed load sub-matrix of water pressure and described the calculation procedures of hydro-mechanical coupling analysis in the framework of DDA. Then, the correctness of the coupling model was verified respectively through analyses of buoyancy, deformation of a block under uniform water pressure and hydraulic fracturing. Finally, the model was applied to evaluate the sliding stability of a gravity dam foundation in China. The failure process and stability factor were calculated by two different stability evaluation methods (the strength reduction method and the overloading method), and the obtained stability factors were compared with those solved by the commonly used limit equilibrium analysis methods. The strength reduction method revealed that the rock strata of dam foundation slide with different displacements along several weak interlayers of different depths, whereas the overloading method revealed that the rock strata slide mainly along a special interlayer beneath the anti-sliding concrete stud, which was designed to be near the dam heel. The DDA method clearly shows the process of rock block failure and profoundly reveals the difference in sliding mode caused by using different stability evaluation methods.

Safety Criteria and Standards for Bearing Capacity of Foundation

This paper focuses on the evaluation standards of factor of safety for foundation stability analysis. The problem of foundation stability is analyzed via the methods of risk analysis of engineering structures and reliability‐based design, and the factor of safety for foundation stability is determined by using bearing capacity safety‐factor method (BSFM) and strength safety‐factor method (SSFM). Based on a typical example, the admissible factors of safety were calibrated with a target reliability index specified in relevant standards. Two safety criteria and their standards of bearing capacity of foundation for these two methods (BSFM and SSFM) were established. The universality of the safety criteria and their standards for foundation reliability was verified based on the concept of the ratio of safety margin (RSM).

Test Investigation on Liquefied Deformation Structure in Saturated Lime‐Mud Composites Triggered by Strong Earthquakes

AbstractThree identical model boxes were made from transparent plexiglass and angle iron. Using the method of sinking water and according to the sedimentary rhythm of saturated calcium carbonate (lime‐mud) intercalated with cohesive soil, calcites with particle sizes diameters of ≤ 5 μm, 10–15 μm and 23–30 μm as well as cohesive soil were sunk alternatively in water of three boxes to build three test models, each of which has a specific size of calcite. Pore water pressure gauges were buried in lime‐mud layers at different depths in each model, and connected with a computer system to collect pore water pressures. By means of soil tests, physical property parameters and plasticity indices (Ip) were obtained for various grain‐sized saturated lime‐muds. The lime‐muds with Ip ranging from 6.3 to 8.5 (lower than 10) are similar to liquid saturated silt in the physical nature, indicating that saturated silt can be liquefied once induced by a strong earthquake. One model cart was pushed quickly along the length direction of the model so that its rigid wheels collided violently with the stone stair, thus generating an artificial earthquake with seismic wave magnitude greater than VI degree. When unidirectional cyclic seismic load of horizontal compression‐tension‐shear was imposed on the soil layers in the model, enough great pore water pressure has been accumulated within pores of lime‐mud, resulting in liquefaction of lime‐mud layers. Meanwhile, micro‐fractures formed in each soil layer provided channels for liquefaction dewatering, resulting in formation of macroscopic liquefaction deformation, such as liquefied lime‐mud volcanoes, liquefied diapir structures, vein‐like liquefied structures and liquefied curls, etc. Splendid liquefied lime‐mud eruption lasted for two to three hours, which is similar to the sand volcano eruption induced by strong earthquake. However, under the same artificial seismic conditions, development of macroscopic liquefied structures in three experimental models varied in shape, depth and quantity, indicating that excess pore water pressure ratios at initial liquefaction stage and complete liquefaction varied with depth. With size increasing of calcite particle in lime‐mud, liquefied depth and deformation extent increase accordingly. The simulation test verifies for the first time that strong earthquakes may cause violent liquefaction of saturated lime‐mud composed of micron‐size calcite particles, uncovering the puzzled issue whether seafloor lime‐mud can be liquefied under strong earthquake. This study not only provides the latest simulation data for explaining the earthquake‐induced liquefied deformations of saturated lime‐mud and seismic sedimentary events, but also is of great significance for analysis of foundation stability in marine engineering built on the soft calcium carbonate layers in neritic environment.

Wave-induced multi-layered seabed response around a buried pipeline

The subject of the wave–seabed–structure interaction is important for geotechnical and coastal engineering regarding stability analysis of foundations for offshore structures. Most previous theoretical investigations available concerned only with such a pipeline in a uniform single layer seabed. In this paper, a wave–seabed–pipeline system is modeled using finite elements. The seabed is treated as porous medium and characterized by Biot's dynamic equations. To explore the mechanism of the seabed instability, the two possible formulations: partly dynamic (u–p model) and fully dynamic (u–w model) for the wave-induced seabed response are considered. Verification of the proposed model is performed against the previous analytical result and experimental data. Based on the numerical results, the effects of wave and seabed characteristics, such as water depth, permeability, shear modulus, degree of saturation, and pipeline buried depth, on the wave-induced excess pore pressure and vertical effective stress will be examined. Finally, a parametric study will be conducted to examine the effects of wave and soil characteristics on the liquefaction potential. It is worth noting that soil permeability has a very significant influence on the pore pressure generation and liquefaction.

Numerical Analysis of Seismic Dynamic Response of Saturated Porous Seabed Around a Buried Pipeline

The stability of submarine pipelines has been extensively studied by coastal engineers in recent years. Seismic-induced pore pressure and effective stresses in the saturated porous seabed and pipeline are the main important factors in the analysis of foundation stability around submarine pipelines. The majority research of the seismic-induced dynamic response around an offshore pipeline has been limited to two-dimension cases. In this paper, a three-dimensional finite element model including buried pipeline is established by extending DYNE3WAC. Based on the proposed numerical model, a parametric study is conducted to examine the effects of soil characteristics and pipeline configurations on the seismic-induced soil response around offshore pipelines.

Forensic Diagnosis on Flood-Induced Bridge Failure. II: Framework of Quantitative Assessment

ThefailureoftheShuang-YuanBridgeinTaiwancausedby floodsassociatedwithTyphoonMorakotinAugust2009promptedthis forensic investigation into its causes. The investigation found multiple factors for the bridge failure: (1) flood flows, (2) river-bend-induced skewed flow, and (3) the effects induced by extended foundation caps and rafted woody debris. A qualitative assessment framework, which includes hydraulic computation, a fluid-solid-coupled model, and foundation stability analysis, is introduced to develop scenario simulations and forensic diagnosis to identify the main causes of the bridge failure. The watershed-wide and local hydraulic conditions are reconstructed using hydraulic computation. The flow field, dynamic water-pressure distributions, scour formation, flood resistance, and flood thrust are ef- ficiently simulated using a fluid-solid-coupled model and foundation stability analysis around the bridge foundations under different hydraulic and environmental conditions. The forensic diagnosis results show that river flooding, extended foundations, skewed flow, and rafted wood aggravated the scour depths and undermined the flood-resistant capacity of the bridge at different severities. In particular, rafted wood contrib- utedtoindividualfracturingofthebridgepiles.DOI:10.1061/(ASCE)CF.1943-5509.0000393. © 2014 American Society of Civil Engineers. Author keywords: Scenario simulation; Forensic diagnosis; Hydraulic computation; Fluid-solid-coupled model; Foundation stability analysis; Scour; Overflood; Skewed flow; Rafted wood debris.

3D models for wave-induced pore pressures near breakwater heads

Wave-induced pore pressure is one of the important factors in the analysis of foundation stability around coastal structures. Existing models for the wave-induced seabed response around breakwater heads have been limited to poro-elastic soil behavior and de-coupled oscillatory and residual mechanisms for the rise in excess pore water pressure. To overcome the shortcoming of the existing models, in this study a new three-dimensional poro-elastoplastic model is established, in which both oscillatory and residual mechanisms can be simulated simultaneously. The reduced cases of the proposed model are verified with existing 2D experimental data available and a 3D poro-elastic analytical solution in front of a breakwater. With the proposed new model, a parametric study is conducted to investigate the relative differences of the predictions of the wave-induced pore pressure and liquefaction with poro-elastic and poro-elasto-plastic models. Based on numerical examples, it can be concluded that relative differences between elastic and elasto-plastic models are significantly affected by wave periods and water depths. Wave height significantly affects the development of residual pore pressure versus time. Plastic soil behavior plays an important role in a seabed of low permeability. Plastic soil behavior has more significant influence on wave-induced residual pore pressure than the amplitude of the oscillating pore pressure. Furthermore, poro-elastic analysis tends to under-estimate the size of the liquefaction regions around breakwater heads.

Use of inert C&D materials for seawall foundation: Quality control measures

The technical viability of using inert construction and demolition (C&D) materials for the construction of seawall and breakwater foundations has been established by laboratory testing of the materials, numerical analysis of foundation stability, and a pilot field-scale engineering performance evaluation. However, quality control measures are still required so that only suitable materials are used for seawall and breakwater foundation construction. The development of different quality control measures for different site conditions is presented in this paper. The rationale, practicality, and implementation of these quality control measures are also discussed.

Wave-induced seabed instability around a buried pipeline in a poro-elastic seabed

The subject of the wave–seabed–structure interaction is important for civil engineers regarding stability analysis of foundations for offshore installations. Most previous investigations have been concerned with such a problem in the vicinity of a simple structure such as a vertical wall. For more complicated structures such as a pipeline, the phenomenon of the wave–seabed–structure has not been fully understood. This paper proposes a finite-difference model in a curvilinear coordinate system to investigate the wave-induced seabed response in a porous seabed around a pipeline. Based on the present numerical model, mechanism of the wave-induced soil response is examined. Employing Mohr–Coulomb failure criterion, the wave-induced seabed instability is also estimated. The numerical results indicate the importance of the effect of pipeline on the seabed response.

The effects of variable permeability on the wave-induced seabed response

The topic of wave-seabed interaction is important for civil engineers with regard to stability analysis of foundations for offshore structures. Most previous investigations of such problems have simply assumed a seabed with uniform permeability, even if the evidence of variable permeability has been reported in the literature. This paper presents a finite-element model for investigating the wave-induced seabed response in a porous seabed, with variable permeability as a function of burial depth. The present finite formulation is established by using a combination of semi-analytical techniques and the Galerkin method. Based on the present numerical model, together with the Mohr-Coulomb failure criterion, the wave-induced seabed instability is estimated. The numerical results indicate that variable permeability affects the wave-induced seabed instability significantly, especially for gravelled seabeds.

Block theory techniques used in arch dam foundation stability analysis

Abstract Geotechnical engineers at the U.S. Bureau of Reclamation use Block Theory , Goodman, Shi 1985, computer programs to aid in analyzing the stability of arch dam foundations. The three-dimensional geometry of foundation blocks in combination with the uplift pressures and dam loads control the resultant force orientation relative to the sliding plane orientations and hence control the analysis results. These foundation block plane orientations combined with their friction angles define the foundation block limit equilibrium. Foundation maps including geologic and topographic features, construction photographs, drill logs, and joint surveys are used to locate and orient joints in the rock mass. The block theory programs are used to calculate most of the quantities needed to visualize, characterize, and quantify the abutment stability. The programs can quickly determine the uplift forces, failure mode, and static safety factors for specific external loads and shear strength parameters. The programs provide realistic geometries helpful in designing drainage and reinforcement systems. The mathematical basis and graphical output of the programs makes them very reliable and provides inherent checks on the results. The effectiveness and practicality of these programs is illustrated in the Bartlett Dam foundation stability analysis and in a second hypothetical example.

Probabilistic foundation stability analysis : Ronold, K O Int J Num Anal Meth GeomechV14, N4, May 1990, P279–296

Probabilistic foundation stability analysis : Ronold, K O Int J Num Anal Meth GeomechV14, N4, May 1990, P279–296

Probabilistic foundation stability analysis

AbstractA probabilistic model for stability analysis of a deepwater gravity‐based platform foundation is defined, based on theory for wave loading in conjunction with conventional slip surface considerations. The model accounts for uncertainties in loading as well as in soil properties, and model uncertainties are also considered. The model is updated through in‐service measurements of some of the governing variables, and measurement uncertainties are included. The practical application of the model is illustrated by presentation of calculations for a typical foundation. Probability calculations are performed by first‐order reliability methods.

Reliability analysis of foundation stability for gravity platforms in the North Sea : Can Geotech J V26, N3, Aug 1989, P359–368

The uncertainties encountered in the evaluation of foundation stability for four offshore gravity structures in the North Sea are reviewed. The uncertainties include those about the load, the material type, the material strength, and the analytical method. The means and coefficients of variations of these are used as inputs to compute the mean and coefficient of variation of the safety factor and the reliability index. The latter are used to assess the effect of various options in site exploration and strength measurement on foundation reliability. Key words: foundation, gravity platforms, offshore structures, probability, reliability, shear strength, site investigation, stability.

Foundation design for deepwater gravity base structure with long skirts on soft soils : Tjelta, T I; Skotheim, A A; Svano, G Proc BOSS'88, Trondheim, June 1988V1, P173–192. Publ Trondheim: Tapir, 1988

The Gullfaks C structure when installed in 1989 will have extended North Sea substructure technology on many frontiers, e.g. deepest water, heaviest concrete base, and greatest environmental loadings, on a site with multilayered soft and geotechnically complex soil conditions. The paper reviews some of the geotechnical aspects related to the novel engineering solutions used, particularly the 22m long concrete diaphragm skirts that have requires extensive in situ field tests and laboratory investigations together with advanced foundation analysis. This paper includes a comparison and discussion of results from foundation stability analysis and comments on load transfer and contained highly stresses zones.

Reliability analysis of foundation stability for gravity platforms in the North Sea

The uncertainties encountered in the evaluation of foundation stability for four offshore gravity structures in the North Sea are reviewed. The uncertainties include those about the load, the material type, the material strength, and the analytical method. The means and coefficients of variations of these are used as inputs to compute the mean and coefficient of variation of the safety factor and the reliability index. The latter are used to assess the effect of various options in site exploration and strength measurement on foundation reliability. Key words: foundation, gravity platforms, offshore structures, probability, reliability, shear strength, site investigation, stability.