Settlement Of Footings Research Articles

A neural network approach for the reliability analysis on failure of shallow foundations on cohesive soils

A collection of feed forward neural networks (FNN) for estimating the limit pressure load and the according displacements at limit state of a footing settlement is presented. The training procedure is through supervised learning with error loss function the mean squared error norm. The input dataset is originated from Monte Carlo simulations for a variety of loadings and stochastic uncertainty of the material of the clayey soil domain. The material yield function is the Modified Cam Clay model. The accuracy of the FNN’s is in terms of relative error no more than 10-5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-5}$$\\end{document} and this applies to all output variables. Furthermore, the epochs of the training of the FNN’s required for construction are found to be small in amount, in the order of magnitude of 90,000, leading to an alleviated data cost and computational expense. The input uncertainty of Karhunen Loeve random field sum appears to provide the most detrimental values for the displacement field of the soil domain. The most unfavorable situation for the displacement field result to limit displacements in the order of magnitude of 0.05 m, that may result to structural collapse if they appear to the founded structure. These series can provide an easy and reliable estimation for the failure of shallow foundation and therefore it can be a useful implement for geotechnical engineering analysis and design.

Cumulative deformation behavior of GRS bridge abutments under cyclic traffic loading

This paper presents an experimental study on reduced scale geosynthetic reinforced soil (GRS) abutment models subjected to cyclic traffic loading, aimed at investigating the influences of cyclic load amplitude, self-weight of bridge superstructure, and reinforcement vertical spacing on the cumulative deformations. The GRS abutment models were constructed using sand backfill and geogrid reinforcement. A static load was first applied to account for the self-weight of bridge superstructure, and then the cyclic loads were applied in several phases with increasing amplitude. The results indicate that significant cumulative footing settlement under cyclic loading mainly occurs within the first few hundred loading cycles, and the settlement increases with increasing cyclic load amplitude. The cyclic load amplitude and reinforcement vertical spacing have significant impacts on the cumulative deformations of GRS abutments under cyclic loading. The maximum facing displacement under cyclic loading occurs near the top of the wall. The cyclic load has a greater impact on the reinforcement strains near the upper middle reinforcement layers, while it has a smaller impact on the lower reinforcement layers.

Experimental study on a new type of FBG-3D printed geogrid in embankment reinforcement

Fiber Bragg Grating (FBG) has been widely used in many civil engineering applications to sense strains and deformations. Combining the advantages of geosynthetics and FBG, this paper creatively presents a new type of FBG-3D printed geogrid, which allows reinforcement and accurate deformation monitoring. Geogrid is directly used as the packaging structure of FBG sensor, and the complete coordinated deformation between the grating monitoring areas of FBG sensor and geogrid is obtained through calibration test. A series of model tests were carried out with FBG-3D printed geogrid to study the influence of reinforcement layers and reinforcement spacing on the bearing capacity and deformation of embankment under cyclic loading. The test results showed that geogrid effectively improved the footing settlement, slope displacement of reinforced embankment under cyclic load, and the effect was more obvious with the decrease of geogrid spacing. The strain data inside the embankment was accurately collected by FBG sensors. Relevant research provides valuable suggestions for the development and application of new geosynthetics.

Rocking foundations on geosynthetic-improved sand

This study focuses on the load-deformation response of a heavily loaded rocking footing on geogrid-reinforced sand via centrifuge-model scale shake table tests. To mitigate issues observed with overturning failure and excessive settlement of shallow footings on unimproved ground, geogrid reinforcement can help control footing kinematics while maintaining the enhanced energy dissipation of a rocking footing. The scalemodel geogrid evaluated in this study was manufactured with 3D printing and placed at a depth equal to the footing width. Shake sequences induced controlled yielding, and the geogrid was observed to reduce settlement during rocking and preserved recentering under strong shaking.

The effects of excavating twin tunnels during cyclic loading on the progressive settlement of existing footing

Tunnels may be constructed in a pair undercrossing existing geotechnical structures exposed to cyclic loading. Such construction changes the stress state in the ground in different ways regarding the tunnelling sequence and would lead to large settlement or even failure to those structures under cyclic loading. Large physical model tests were carried out to examine the impact of excavating twin tunnels during cyclic loading on the progressive settlement of footings. The vertical soil stress, footing settlement and ground deformation were analysed regarding different construction sequences and spacings between twin tunnels. The results indicate that previous cyclic loading history affects the alteration of soil stress caused by tunnelling activity. Compared with excavating twin tunnels successively, excavating the tunnels in sequence leads to greater settlement caused by the subsequent cyclic loading. The change in the relative density of soil is invalid to explain the enlargement of the settlement. Finite element analysis was performed to investigate the mechanism of the effects of excavating twin tunnels during cyclic loading on the footing settlement. It was found that the increase of footing settlement in the subsequent cyclic loading and the greater settlement in the sequential tunnelling case are attributed to the greater stress ratio (q/p) in the ground.

Hazard Curves for Reliability Assessment of Strip Footings on Spatially Varying Cohesive Soils

The present study aimed to create a series of hazard curves against maximum total settlement and angular rotation of strip footings for probabilistic shallow foundation design on clays. Random field finite element method (RFEM) was adopted with elasto-plastic clay-like soil behavior, deformation modulus (Ed) and shear strength parameters (c and ) were employed as random field inputs. Parameters were defined and assigned to the analysis models with varying correlation lengths (h, v). Models have been iteratively solved one thousand times, and output distributions of maximum settlement and angular rotations were recorded. Probability density functions (PDF) were fitted to the outputs, and probability of failure (Pf) for footing deformation limits was subsequently estimated. Proposed hazard curves for two anisotropy and three variability categories were developed employing the estimated Pfs. The method proposed has been validated using an independent database of in-situ results, and a worked example was provided to illustrate the implementation of the process. The key contribution of the research is to form hazard curves for shallow foundations considering elasto-plastic soil behavior with the impact of all influencing parameters, respecting the limit values for foundation deformation in the design codes. The proposed technique offers a probabilistic evaluation of strip footings with spatial variation of clayey soils and a valid method for the reliability-based design of foundations in the serviceability limit state.

Experimental and numerical study for seismic response of strip footing on slopes

The present study investigates the free-field response of slopes as well as the seismic response of strip footing on slopes. The small-scaled physical model tests (PMT) have been performed under one-directional excitation. The sinusoidal waves of different amplitudes and frequencies are applied at the base of the model. To examine the kinematic interaction between the footing and slope, a rigid strip footing is placed at the center of the slope. The free-field response of the slope as well as the seismic response of the footing on the slope from PMT is determined using digital image correlation (DIC). Two-dimensional finite element analysis (FEA) has been carried out to simulate the PMT results. No study has been reported in the literature considering both experimental and numerical work. Further, the effects of increasing load on the footing on slopes have not been examined yet. Results from PMT and FEA are found in good agreement. The maximum amplification is observed near the crest for free-field response of slope. For both horizontal ground surface and sloping ground, the maximum amplification occurs at the frequency of excitation. However, some small peaks at other frequencies are also observed for the sloping ground due to the reflection of waves from the sloping surface. The seismic settlement of strip footing is increased with the increase of slope angle, amplitude and frequency of the excitation. However, the seismic settlement decreases with the increase in footing width and edge distance of footing from the slope. For footing on slope, the maximum amplification is observed at the center of the slope. A large settlement of footing is observed when the footing is heavily loaded (e.g., 80% of the ultimate bearing capacity of footing).

Physical Modeling of the Effect of Using Scaled Geosynthetic Reinforcements on Bearing Capacity and Settlement of Strip Footing

This study evaluated the strip foundation bearing capacity and settlement on sandy soil reinforced with scaled geocomposite and geotextile by laboratory model testing. Therefore, several reinforcement compounds were used in different layers (one to four), including identical and various vertical distances from each other and the footing base. The geocomposite used in this study consisted of geogrid and geotextile layers. The most crucial consideration in this research was the application of scaled reinforcement with a factor of 7.5 to create more precise laboratory models. Based on the results, all models failed in the lower settlement, which in most cases was 7% of the width of the footing. Test results indicated that the maximum increasing factor in bearing pressure of foundation in the case of ultimate bearing was 3.4, which could be related to using four layers of geocomposite at optimal distances. The percentage of decreasing footing settlement at the maximum value was about 86% in the two-layer geocomposite state. Its value remained constant with increasing number of layers. Percentage variation in bearing capacity value indicated that geotextile had a better performance in increasing the bearing capacity at the high settlement level. It was close to the values of the geocomposite.

Finite Element Modeling of a Stone Layer Under a Strip Footing to Estimate Soil Behavior and Determine Optimal Stone Layer Width and Depth

Various methods can be applied to improve soil behavior in order to increase the bearing capacity or reduce the settlement of footings. These methods can be categorized as stabilization or improvement of soil by use of different geosynthetics; injection methods; grouting or replacing weak soil with stronger materials. One of the most common methods and materials that can be used for improving soils, is placing a stone layer under the footing. In this study, a stone layer under a strip footing is simulated with the finite element method (FEM) to estimate the soil behavior in different conditions. A strip footing with a width of 1m and length of 8m with a 100 kN/m2 uniform load was modelled. Different widths of stone layer from 1B to 3B (B was the strip footing width) with different depths of 0.5B, 1B, 1.5B, and 2B were modelled in Plaxis 3D and results were obtained from the simulation. By reviewing the results, it was found that the optimum dimensions of the stone layer to place under the presented strip footing was 2B width and 1B depth. This result can be applied to real projects with similar conditions.

Prediction of the Bearing Capacity of Composite Grounds Made of Geogrid-Reinforced Sand over Encased Stone Columns Floating in Soft Soil Using a White-Box Machine Learning Model

Stone columns have been extensively advocated as a traditional approach to increase the undrained bearing capacity and reduce the settlement of footings sitting on cohesive ground. However, due to the complex interaction between the soil and the stone columns, there currently needs to be a commonly acknowledged approach that can be used to precisely predict the undrained bearing capacity of the system. For this reason, the bearing capacity of a sandy bed reinforced with geogrid and sitting above a collection of geogrid-encased stone columns floating in soft clay was studied in this research. Using a white-box machine learning (ML) technique called Multivariate Polynomial Regression (MPR), this work aims to develop a model for predicting the bearing capacity of the referred foundation system. For this purpose, two hundred and forty-five experimental results were collected from the literature. In addition, the model was compared to two other ML models, namely, a black-box model known as Random Forest (RF) and a white-box ML model called Linear Regression (LR). In terms of R2 (coefficient of determination) and RMSE (Root Mean Absolute Error) values, the newly proposed model outperforms the two other referred models and demonstrates robust estimation capabilities. In addition, a parametric analysis was carried out to determine the contribution of each input variable and its relative significance on the output.

The effects of undercrossing tunnelling on the settlement of footings subjected to cyclic loading

In urban areas, due to the expansion of underground systems and space limitation, many tunnels will be constructed beneath existing tunnels, roads or railways which may be subjected to traffic loading. Undercrossing tunnelling disturbs the stress state in soils and may affect the long-term settlement behaviour of existing structures under cyclic loading. A series of physical model tests were performed to investigate the effects of undercrossing tunnelling on the settlement behaviour of existing footings subjected to cyclic loading. The undercrossing tunnelling induced volume loss is simulated using a self-designed device in steps between loading cycles. The variation of footing settlement and soil stresses in the ground are presented and discussed under different cyclic loading amplitudes, volume losses and footing positions relative to the new tunnel. The results indicate that including volume loss between loading cycles enlarges the footing settlement during the subsequent cyclic loading, even if the footing is out of tunnelling induced settlement profile, and the greater the volume loss, the greater the enlargement. The enlargement decreases as the footing gets farther away from the new tunnel. The enlargement is attributed to the change of relative density and/or the change of stress state in the soil induced by tunnelling.

Prediction of the Settlement and Long-Term Bearing Capacity of Rectangular Footing

Prediction of the Settlement and Long-Term Bearing Capacity of Rectangular Footing

Performance-based seismic design of rocking shallow foundations in cohesive soil: Methodology and numerical validation

The concept of rocking shallow foundation as a base isolation mechanism has been incorporated into seismic design guidelines, but a feasible design method is yet to be developed. This research proposes a performance-based seismic design (PBSD) for bridges supported on rocking shallow foundations in cohesive soils. This PBSD considers three performance indicators: maximum drift, residual footing rotation and residual settlement. Empirical correlations to obtain the secant stiffness, hysteresis damping ratios, re-centering ratio and residual settlement were obtained from preceding field tests. The PBSD was elaborated with two examples for which the shallow foundation of an as-built highway overpass bridge was re-designed in two presumed cohesive soil sites. The performance of the re-designed bridge was further verified using nonlinear time history analyses. A numerical model was developed, calibrated, and validated using field test results. The maximum and residual drifts and residual footing settlement at the design level earthquakes obtained from numerical modeling were shown to satisfy the performance criteria.

Influence of spatial variability of soil elastic modulus on elastic settlement of rectangular footing under fuzzy uncertainty

Influence of spatial variability of soil elastic modulus on elastic settlement of rectangular footing under fuzzy uncertainty

Discussion of “Settlement of Footings on Compacted and Natural Collapsible Soils upon Loading and Soaking’’ by Roger Augusto Rodrigues, Fabio Visnadi Prado Soares, and Marcelo Sanchez

Discussion of “Settlement of Footings on Compacted and Natural Collapsible Soils upon Loading and Soaking’’ by Roger Augusto Rodrigues, Fabio Visnadi Prado Soares, and Marcelo Sanchez

Effect of sheet pile wall on the load-settlement behaviour of square footing nearby excavation

ABSTRACT Due to the shortage of urban land, new buildings are constructed adjacent to old buildings. In this regard, there is limited information about the behaviour of the shallow foundations adjacent to the excavation. In this research, a series of experimental and numerical studies are conducted on reinforced and unreinforced granular soils adjacent to excavation loaded with square footings. The experimental results are in good agreement with the numerical study. Numerical investigations were carried out on sandy excavation by varying the footing distance from the edge of the different granular excavations. It was found that by using three reinforcing layers, the ultimate bearing capacity would increase. Additionally, excavation has no significant effect in the vicinity of 4B, in which B is the footing width. Furthermore, the need to build new large buildings in the vicinity of each other has reduced the distances between square footings and, as a result, has created the phenomenon of interference in the footings and excavation. This occurs through the interference of wedges and rupture surfaces. Since this phenomenon bears a substantial result on the bearing capacity of shallow footings, this work investigates the effect of interference of ruptured wedges on the carriage capacity, settlement, and deformation of square footings. The optimum interference factor is defined at spacings of 2B and 3B for dense and loose reinforced sands, respectively. Furthermore, by including three continuous geogrid layers underneath two square footing interferences, their behaviour will be improved.

Influence of stress relief due to deep excavation on a brick masonry wall: 3D numerical predictions

The effects of tunnel construction on existing brick masonry walls have been extensively investigated, but the influence of deep excavation-induced stress relief is seldom reported in the literature. This paper presents a three-dimensional study to investigate damaging effects on a brick masonry wall (constructed parallel to the diaphragm wall) due to deep excavation at different depths. In addition, the effects of the wall orientation (i.e., orthogonal to the diaphragm wall), wall locations with respect to the deep excavation, and sand density were examined. The hypoplastic sand model was used to capture soil behaviour. The brick masonry wall was modelled with a micro-modelling technique. The traction-separation behaviour of cohesive elements was employed to model the mortar joints. It was found that the maximum settlement was induced at the mid-part of the wall parallel to the diaphragm wall. The induced settlement resulted in developed cracks in the wall. In the orthogonal case, the wall was bended downward, behaving like a cantilever beam. Negligible footing settlements were observed when the wall was located at a distance exceeding 0.48He (excavation depth) from the diaphragm wall. By increasing the relative density from 30% to 90%, the induced footing settlement decreased by up to 72%.

Probabilistic Failure Estimation of an Oblique Loaded Footing Settlement on Cohesive Geomaterials with a Modified Cam Clay Material Yield Function

In this work, a quantitative uncertainty estimation of the random distribution of the soil material properties to the probability density functions of the failure load and failure displacements of a shallow foundation loaded with an oblique load is portrayed. A modified Cam Clay yield constitutive model is adopted with a stochastic finite element model. The random distribution of the reload path inclination κ, the critical state line inclination c of the soil and the permeability k of the Darcian water flow relation, has been assessed with Monte Carlo simulations accelerated by using Latin hypercube sampling. It is proven that both failure load and failure displacements follow Gaussian normal distribution despite the excessive non-linear behaviour of the soil. In addition, as the obliquity increases the mean value of failure load and the failure displacement always increases. The uncertainty of the output failure stress with the increase of the obliquity of the load remains the same. The failure spline of clays can be calculated within an acceptable accuracy with the proposed numerical scheme in every possible geometry and load conditions, considering the obliquity of the load in conjunction with non-linear constitutive relations.

Experimental Investigation of Square Footing Resting on Gypseous Soils Contaminated by Kerosene

This study investigated the behavior of square footing (Length = 100 mm) constructed over a gypseous soil contaminated with four percentages of kerosene (5, 10, 15, and 20%) and several thicknesses of the contaminated soil (0.5B, B, and 1.5B) was taken from Tikrit University in Salah Al-Deen governorate from the depth of (1.5-2) m under natural ground level. The tests revealed that the soil is high gypsum content (62%). The main loading tests of the gypseous soil were carried out [field density (dry) and field density (with soaking)] which are a reference for comparison with the contaminated gypseous soil loading tests. The results that are represented by the relationship between pressure and settlement show that the gypseous soil has a good resistance reached to (385 kN/m2) when compacted to field density before soaking. For the contaminated gypseous soil tests, the bearing capacity does not improve as the bearing capacity is reduced by 50% or more compared to the non-contaminated gypseous soil, as for the settlement there is a slight improvement. As for the soaked gypseous soils, it was showing an improvement in bearing capacity and an improvement in the settlement of footing.

Determination of the ultimate consolidation settlement of jack-up spudcan footings embedded in clays

When jack-up platforms are deployed for long-term services such as those functioning as production units, the consolidation settlement of spudcan footings is an issue of particular concern. Unpredicted and thus unprepared settlement may do harm to the serviceability and safety of jack-up rigs. Through centrifuge experiment and large deformation finite element calculation, this paper first illustrates the inherent correlation between the excess pore pressure dissipation inside soil and spudcan settlement development. With the measured and calculated settlement time histories, subsequent efforts are directed towards exploring how to predict the ultimate consolidation settlement with accuracy. Particular attentions are placed on investigating the applicability and advantages of two observational methods: Asaoka's method and Hyperbolic approach. Their prediction performances for spudcan with various soil, loading, embedment and geometrical conditions are symmetrically evaluated through numerical parametric investigation. The upper and lower limits of their prediction errors are established. Explicit recommendations are given on the selection of appropriate prediction approaches for different consolidation conditions. The practical significance of these research outcomes lies in 1) providing guidance on the selection of settlement prediction approaches; 2) establishing the limits of prediction errors involved. These are expected to be particularly useful for the field monitoring of spudcan settlement.