Settlement Of Shallow Footings Research Articles

Bearing capacity and settlement of shallow footings on liquefiable soil subjected to seismic loading

In liquefying soils, Shallow foundations may experience a reduction in bearing capacity and increase in settlement and tilt due to seismic loading. Therefore, the buildings on shallow footings may settle and tilt excessively. In this paper, the bearing capacity and settlement of shallow foundation on liquefiable deposits has studied. The study includes a shaking table test, reviewing of theoretical equations (available in literature), which estimating settlement of shallow footings due to seismic loading, calibration, and verification of these equations with data from the shaking table test for improved soil by grouting and unimproved soil. It is important to note that the grouting materials used in this study are the CKD and Bentonite slurries. A modification to the seismic bearing capacity and settlement equations had been done to account for the liquefaction state. Good convergence has been gotten between predicted and measured settlement.

Settlement of Shallow Foundations on Cohesionless Soils Based on SPT Value Using Multi-Objective Feature Selection

Accurate prediction of settlement for shallow footings on cohesionless soil is a complex geotechnical problem due to large uncertainties associated with soil. Prediction of the settlement of shallow footings on cohesionless soil is based on in situ tests as it is difficult to find out the properties of soil in the laboratory and standard penetration test (SPT) is the most often used in situ test. In data driven modelling, it is very difficult to choose the optimal input parameters, which will govern the model efficiency along with a better generalization. Feature subset selection involves minimization of both prediction error and the number of features, which are in general mutual conflicting objectives. In this study, a multi-objective optimization technique is used, where a non-dominated sorting genetic algorithm (NSGA II) is combined with a learning algorithm (neural network) to develop a prediction model based on SPT data based on the Pareto optimal front. Pareto optimal front gives the user freedom to choose a model in terms of accuracy and model complexity. It is also shown how NSGA II can be effectively applied to select the optimal parameters and besides minimizing the error rate. The developed model is compared with existing models in terms of different statistical criteria and found to be more efficient.

Settlement Prediction of Footings Using VS

The shear wave velocity (VS) is a key parameter for estimating the deformation characteristics of soil. In order to predict the settlement of shallow footings in granular soil, the VS and the concept of Schmertmann’s framework were adopted. The VS was utilized to represent soil stiffness instead of cone tip resistance (qc) because the VS can be directly related to the small-strain shear modulus. By combining the VS measured in the field and the modulus reduction curve measured in the laboratory, the deformation characteristics of soil can be reliably estimated. Vertical stress increments were determined using two different profiles of the strain influence factor (Iz) proposed in Schmertmann’s method and that calculated from the theory of elasticity. The corresponding modulus variation was determined by considering the stress level and strain at each depth. This state-dependent stress-strain relationship was utilized to calculate the settlement of footings based on the theory of elasticity. To verify the developed method, geotechnical centrifuge tests were carried out. The VS profiles were measured before each loading test, and the load-settlement curves were obtained during the tests. Comparisons between the measured and estimated load-settlement curves showed that the developed method adequately predicts the settlement of footings, especially for over-consolidated ground conditions.

Impact of adjacent footings on immediate settlement of shallow footings

When the settlement of a footing under a structure is estimated by considering the bearing pressure of that footing only, the estimated value of the settlement may not be good enough since the other neighboring footings are going to effect the settlement of the footing under consideration also. Thus, in the settlement estimation of a footing, the effect of neighboring footings must be considered. In this study, impact of adjacent footings is considered on the estimation of elastic settlement of shallow foundations. In the estimation of elastic (immediate) settlement, the Schmertmann’s method that is a very popular method in the elastic settlement estimation of shallow foundations is employed. In order to consider effect of neighboring footings on elastic settlement of main footing in different configurations, a MATLAB script has been generated. Elastic settlements of the various configurations are estimated by the script and several conclusions have been reached.

Settlement of shallow footings on layered soil: state-of-the-art

Shallow footings form the foundations of conventional structures like residential as well as industrial framed buildings and also other industrial structures like silos, chimneys, cooling towers, overhead tanks, etc. The foundations are checked both for shear failure and settlement criterion. Most of the conventional analyses consider the soil to be homogeneous, however, soil strata comprise of different soil layers with inherent variability. Several analytical, numerical, and experimental research works are available for the analysis of shallow footings on layered soil system. This paper presents comprehensive overview of literature pertaining to the settlement analysis of shallow foundations on layered soil system. It was aimed to provide all the references at one place to facilitate the research workers in this area. Deterministic as well as probabilistic studies have been compiled and it is felt that deterministic methods should be used in conjunction with the stochastic approaches for more rational analysis of shallow foundations on layered soils.

Generalized Schmertmann Equation for settlement estimation of shallow footings in saturated and unsaturated sands

Simple relationships are proposed in this paper by modifying the Schmertmann's equation for settlement estimations of footings (i.e., <TEX>$B/L{\approx}1$</TEX>) carrying vertical loads in saturated and unsaturated sandy soils. The modified method is developed using model plate load tests (PLTs) and cone penetration tests (CPTs) results conducted in saturated and unsaturated sand in a controlled laboratory environment. Seven in-situ large-scale footings tested under both saturated and unsaturated conditions in sands were used to validate the proposed technique. The results of the study are encouraging as they provide reliable estimates of the settlement of shallow footings in both saturated and unsaturated sands using the conventional CPT results.

Resistance factors for settlement design

To control serviceability problems arising from excessive settlement of shallow footings, geotechnical design codes generally include specifications regarding maximum settlement, which often govern the footing design. Once the footing has been designed and constructed, the actual settlement it experiences on a real three-dimensional soil mass can be quite different than expected, due to the soil's spatial variability. Because of this generally large variability (compared to other engineering materials, such as concrete and steel) and because this particular serviceability limit state often governs the design, it makes sense to consider a reliability-based approach to settlement design. This paper looks in some detail at a load and resistance factor design (LRFD) approach to limiting footing settlement. In particular, the resistance factors required to achieve a certain level of settlement reliability as a function of soil variability and site investigation intensity are determined analytically using random field theory. Simplified approximate relationships are proposed and tested using simulation via the random finite element method. It is found that the simplified relationships are validated both by theory and simulation and so can be used to augment the calibration of geotechnical LRFD code provisions with respect to shallow foundation settlement. Key words: reliability-based design, settlement, geotechnical, shallow foundation, random field, probability.

Prediction of settlement of shallow footings on sand: some observations: Giddings, T R Proc Int Conference on Foundations and Tunnels, London, 24–26 March 1987V1, P20–24. Publ Edinburgh: Engineering Technics Press, 1987

Prediction of settlement of shallow footings on sand: some observations: Giddings, T R Proc Int Conference on Foundations and Tunnels, London, 24–26 March 1987V1, P20–24. Publ Edinburgh: Engineering Technics Press, 1987

Shallow Foundations on Frozen Soil: Creep Settlement

Current methods for estimating the long‐term settlement of shallow foundations on frozen soils are reviewed. It is found that, when the distortional creep is the main source of settlement, there are some potentially good methods for its prediction. Much less is known, however, on how to predict the long‐term settlement of shallow footings on relatively warm frozen soils, when both creep and consolidation act simultaneously. Other subjects considered in the paper are the selection of operational strength of frozen soils for the design, the ways of taking into account the effect of friction on their creep and strength, as well as the effects on the settlement of foundations of the depth of burial and the loading history. Finally, some areas of needed research are defined, with a special emphasis on the need for more long‐term performance observations on full‐scale footings in permafrost.