Strip Foundation Research Articles

The influence of the parameters of engineering protective structures on the effectiveness of their use in densely built-up territory

A study of the influence of application of an engineering protective screen made of small-diameter driven piles on the existing building deformations, caused by the arrangement of the pit fence made of bored piles, was carried out. The study was carried out with the help of numerical modeling using the method of finite elements, which allowed to display the work of the system "soil base - engineering protective structures - the foundation of the existing building" with different parameters of the protective screen. The influence of the following parameters is shown:
 1) the depth of laying the protective screen L in relation to the depth of the compressible soil zone (Hst).
 2) the position of the protective screen between the retaining structures of the pit and the existing building.
 3) rigidity of the screen – the ratio of the step to the diameter of the piles of the engineering protective screen.
 4) the distance between the existing building and the pit in relation to the depth of the enclosing structures of the pit of the new construction.
 The tasks were modeled in a spatial arrangement with the task of the system "soil base - enclosing constructions of the pit - protective screen - foundations of the existing building". The soil environment was modeled using the Hardening Soil Model. The calculation was carried out in stages.
 The variation of the parameters of the protective screen was carried out for the historical building, which in most cases was made according to a rigid wall construction scheme with strip foundations.
 The foundation depth is 1.2 - 3.0 m and the foundation width is 1-2 m. The average pressure under the foundation is 150-250 kPa.
 The rational depth of the foundation and the position of the protective screen between the existing building and the pit of the new construction were established.
 The area of effective application of the protective screen was revealed, depending on the distance between the building and the pit fence.
 The effective stiffness is established depending on the change in the relative distance between the poles of the protective screen.

Advanced FELA-ANN framework for developing 3D failure envelopes for strip foundations on anisotropic clays

Advanced FELA-ANN framework for developing 3D failure envelopes for strip foundations on anisotropic clays

Towards the saving potentials using a hybrid topology optimization: Application of a coupled deterministic and empirical approach solving a geotechnical optimization problem

AbstractThis article presents the application of the TOSS (topology optimization for stiffness and strength) algorithm, a hybrid optimization strategy for topology optimization, used for the design of a strip foundation as a basic geotechnical structure. One of the challenges of this field is to improve structural performance by using less material than conventional structures. Therefore, the SIMP (solid isotropic material with penalization) is applied to optimize the foundation concerning its deformational behavior. The downstream SKO (soft kill option) then solves for optimality concerning the foundation's stress distribution. Numerical experiments with the TOSS algorithm reveal great potential for material savings. The coupled solution presents the benefit of reducing emissions due to material savings of more than 20% in comparison to the individual SIMP and SKO algorithms. A positive by‐product of the method is that stress peaks under the foundation are reduced due to the homogenization of stresses as a result of SKO optimization, thus creating the conditions for better durability of the foundation.

Application of Artificial Intelligence Techniques to Predict Strip Foundation Capacity Near Slope Surfaces

Application of Artificial Intelligence Techniques to Predict Strip Foundation Capacity Near Slope Surfaces

Analytical Solutions of Water Inflow for Foundation Pit in Confined Water Stratum

This paper is aimed at the problem of inaccurate calculation of the water inflow of a foundation pit with a suspended water-proof curtain in a confined water stratum. According to the groundwater hydraulics principle, the theoretical model of the seepage field of the foundation pit is established, and the analytical formula of the water inflow for the circular, strip, and rectangular foundation pits is deduced. The seepage path influence coefficient α related to the water-proof curtain insertion ratio, the thickness of the confined aquifer, and the radius of the foundation pit is proposed and obtained by the positive and negative analysis of numerical simulation. The coefficient is used to correct the equivalent seepage length in the pit and directly affect the calculation result of water inflow. Finally, based on the calculation results of the analytical solution of water inflow, the relationship between the scale of the foundation pit and the water control effect is discussed. The research results show that the theoretical analysis results in this paper are in good agreement with the numerical results and the measured data in the field: when the size of the foundation pit is too large, it is not suitable to use the suspended water-proof curtain as the water control measure.

Model Test Study on the Response of Two Different Shallow-Foundation Framed Buildings under Tunnel Volume Loss

In order to study the influence of tunnel volume loss on adjacent framed buildings with different shallow foundations, this paper carried out physical model experiments with two common types of footings (isolated and strip footings) under different working conditions based on the digital image correlation (DIC) technique. The main finding of the present paper is that the increase in formation loss rate will aggravate the deformation and damage of the structure, and the strip foundation shows stronger integrity and stability compared with the isolated foundation in this process. With the increase in the eccentricity of the frames with respect to the tunnel, the overall tilt and damage degree of structural elements increases first and then decreases for both foundations, reaching the maximum value with the eccentric distance of one multiple of the tunnel diameter. Interestingly, when the isolated footings are located directly above the tunnel, the damage in the inner panels is the most severe and gradually decreases with eccentricity, changing from a sagging mode to a hogging mode for the frame form. While the strip footings always maintain slight hogging, and the trend of the damage degree of panels is similar to that of elements, with the eccentric distance reaching two times the tunnel diameter, the strip foundation structure tends to be stable, while the isolated one still needs attention for its potential possibility of damage in panels. The research results have reference value for the impact assessment of adjacent shallow-foundation framed buildings in subway tunnel construction.

Emissions-based options appraisal for modular building foundations: a case study

A study was undertaken to evaluate the embodied greenhouse gas emissions of four different design options for the foundation of a residential modular building in the East Midlands, UK. The assessment considered the embodied carbon dioxide equivalent of material production (without and with Portland cement replacement using ground granulated blast-furnace slag), transportation, construction works (such as soil excavation) and plant usage on site and off site. The findings indicated that helical piles and reinforced concrete slabs supported with expanded polystyrene were the most sustainable options (in terms of embodied emissions) compared with conventional strip and pad foundations. This study provides valuable insight into considerations and constraints that may arise when evaluating the sustainability of modular building foundations. It offers practical guidance for decision makers in the modular construction sector seeking to mitigate the environmental impact of their geotechnical design.

The Effect of Different Fiber Reinforcement on Bearing Capacity under Strip Foundation on the Sand Soil: An Experimental Investigation

The aim of this study is to investigate the bearing capacity-settlement behavior of strip footing settling on sand soil randomly reinforced with glass fiber, basalt fiber, macromesh fiber, and four different hybrid fiber additives in which these fibers are used together. Model tests were carried out in the laboratory on the strip footing and placed on the unreinforced and reinforced sand with different fibers. In the study, model tests were carried out on seven types of randomly reinforced soils by using glass, basalt, macrame, and mixtures of these fibers as reinforcement. In the model tests, two different fiber contents, 1% and 2%, and two different fiber lengths, 24 mm and 48 mm, were used. Tests were carried out with Dr = 30% and 50% relative density, and reinforcement depths 1B, 2B, and 3B were selected. In addition, the photographs taken during the test were analyzed with the particle image velocimetry (PIV) method and the displacements on the soil were examined. As a result of the reinforced and unreinforced model tests, the highest ultimate bearing capacity was measured as 680 kPa from the tests with Dr = 50% relative density, 48 mm length, 2% contents, and 3B depth macromesh fiber reinforced. In hybrid fibers, the highest ultimate bearing capacity was measured as 495 kPa, with Dr = 50% relative density, 48 mm length, 2% contents, and 2D depth micromesh and basalt fiber-reinforced tests. In the reinforced tests, it was concluded that the most effective fiber on bearing capacity is macromesh fiber. It can be seen that in the PIV analysis, as the fiber additive increased, the settlements made by the foundation decreased under the same pressure. It has also been observed that adding reinforcement to the soil transfers the stresses occurring in the soil to a wider area.

Finite elements limit analysis formulation using the power type yield criterion for plane strain and axisymmetric stability problems

The current research employs a power type yield criterion which accounts for the dependency of the shear strength parameters, namely, cohesion and internal friction, on stress level which becomes quite effective in obtaining very accurately the solutions of different stability problems in geomechanics involving soil and rock media. The present manuscript introduces plane strain and axisymmetric formulations which deal with the power type yield criterion and are based on the lower and upper bound finite elements limit analysis in conjunction with the power cone programming (PCP). To demonstrate the efficacy of the proposed formulations, the problems of the determination of the bearing capacity of strip and circular foundations in a cohesive-frictional soil medium have been addressed. In the case of a strip footing, the earthquake inertial forces in a horizontal direction have also been incorporated. The adaptive mesh pattern has been employed to improve the accuracy of the solution at the expense of minimal computational effort. The results have been thoroughly validated by making the comparison of the obtained solutions with that reported in literature. The proposed formulations are expected to be quite useful in solving different stability problems in geomechanics.

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.

A New Analytical Approach for Determination of the Bearing Capacity of a Strip Foundation on a Granular Trench

A New Analytical Approach for Determination of the Bearing Capacity of a Strip Foundation on a Granular Trench

СТРІЧКОВИЙ ФУНДАМЕНТ З ПОВЗДОВЖНІМ ВИРІЗОМ ПО ПІДОШВІ МАСИВНОЇ ПІДПІРНОЇ СТІНИ

The paper analyzes the designs of traditional strip foundations with a flat bottom, the load from which causes the plane strain stress state of the soil base, and other variations of conventionally strip (continuous) foundations, which due to their shape (configuration) of the contact area with the base change its stress state, which enables designing more sustainable foundations for continuous buildings and structures. Proceeding from the solutions to the mixed problem of the theory of elasticity and plasticity using the Mohr-Coulomb criterion strength criterion, analytical studies of the development of plastic zones in the base of a strip foundation with a longitudinal cut-out have been conducted, which show that the limit state always occurs first in the foundation’s edge zones, that is, underneath the outer edges of the foundation. It is also noted, however, that the design resistance of soil decreases when there is no additional load in the area of the cut-out; therefore, a patented design has been proposed of a strip foundation with a longitudinal cut-out in the bottom, where the cut-out with the height is filled with low-modulus material to improve the design resistance of soil. Based on experimental and theoretical studies, methods have been proposed for calculating the soil base (design resistance , settlement and inclination ) for a strip foundation of a massive retaining wall with a longitudinal cut-out in the bottom. A real example shows that the total width of the strip foundation with a cut-out is shorter by 1.5 m in comparison with the continuous shape of the bottom of the foundation, which has a significant economic effect on every linear meter of the wall foundation. Overall, the proposed methods make it possible to reasonably design effective eccentrically loaded foundations with cut-outs in the bottom and to improve the permissible vertical pressure on the base in comparison with a continuous bottom, all other things being equal. Keywords: strip foundation, massive retaining wall, eccentricity, bottom, cut-out, soil base, calculation procedure.

The practice of arranging a pit deeper than the level of the soles of the foundations of the surrounding buildings

A rational constructive-technological decision to arrange a fence of a deeper pit for a new building than the depth of laying strip foundations of the surrounding buildings has been substantiated and tested in practice. The decision to arrange the fence was tested based on the results of complex experimental and theoretical studies under the conditions of a wet loess massif. At same time, regulatory restrictions on additional subsidence of these buildings foundations are provided. It has been proven that the additional subsidence of existing objects did not exceed the permissible values according to the norms. This happened due to the arrangement of the pit fence, the phasing of soil extraction in the initial stages under of the soil berm protection. The technology provided for the construction of a pit fence with sheet piling (I-beam No. 30) with a step of 1 m, with timber lagging between them. Then they installed the capping beam, struts, rakers and gradually raised the floor and outer wall of the parking lot of the new building.
 The results of long-term geodetic observations of the foundations deformations of buildings located in the zone of the pit influence of the new building at various construction stages of its enclosure are described.
 Sufficient convergence of the simulation results in the plane condition using the FEM and field studies was determined (the relative error did not exceed 20%). An elastic-plastic soil model of the "basement - foundations of an existing building - pit enclosure" system was used for modeling.
 The article describes examples of the results of FEM modeling of soil massif deformations at various stages of pit fence construction.
 It was determined that during construction the largest horizontal movements of the pit fence vary from 8 to 23 mm in the area of existing buildings.The maximum vertical movements of the bases foundations of these buildings amounted to 10 mm, which does not exceed the permissible values according to the norms.
 Prospects for further research on assessing the level of reliability of the pit enclosure by determining the variability parameters of the components of the system "foundation - foundation of the existing building - pit enclosure" have been determined.

Upper Bound Solution Analysis of the Ultimate Bearing Capacity of Two–Layered Strip Foundation Based on Improved Radial Movement Optimization

Considering the change of different soil layer parameters of a two–layered strip foundation, a planar kinematically permissible multi–block failure mechanism of a two–layered strip foundation under vertical uniform load is formulated. Based on upper–bound limit analysis theorem, the solution process of ultimate bearing capacity of a two–layered strip foundation is proposed. The improved radial movement optimization (IRMO) could search the critical slip surface of the foundation and calculate associated ultimate bearing capacity. On this basis, analyze the influence parameters. The results show that the IRMO algorithm is feasible, stable, and efficient in solving the ultimate bearing capacity. With the increase in the internal friction angle and cohesion of the two–layered strip foundation, the critical slip surface will expand more deeply, and the ultimate bearing capacity will increase. The influence of upper soil parameters on the calculation results is greater than that of lower soil. For the case with upper–hard soil, the ultimate bearing capacity of it increases gradually with the increase in the H/B ratio. For the upper–soft case, the ultimate bearing capacity of it decreases gradually with the increase in the H/B ratio. Moreover, the increase of ground overload will also cause a linear–increasing in the ultimate bearing capacity.

RESULTS OF COMPLEX RESEARCH OF SOIL BASES REINFORCED BY SOIL-CEMENT ELEMENTS MANUFACTURED USING DRILLING MIXING METHOD

Object. To find out the nature of stress-strain state of strip foundations reinforced by drilling mixing technology by means of experimental studies in a tray and in field conditions, for the reliability of the obtained results, comparing field studies with finite element method (FEM) modeling. Method. Tray tests were carried out in a metal tray with a steel stamp. Unreinforced clay soil bases and bases reinforced by soil-cement were tested with varying values of the reinforcement coefficient from 2,1 % to 7,1 % with a reinforcement depth of 100 mm and a diameter of 5 mm. Observations of settlements of the natural object were carried out by the method of geometric leveling using deformation marks arranged evenly around the perimeter of the building. The site on which a ten-story residential building was built was chosen due to difficult engineering and geological conditions. The zero cycle of observations was carried out, cycles after the construction of each floor of the building, its acceptance for operation, occupancy of the building and every subsequent 2-3 years. Results. The load-bearing capacity of the foundations with the increase in the percentage of soil reinforcement increases with the given parameters in an approximately linear dependence. The given results demonstrate a high correspondence between the experimental and simulated dependences of settlements on pressure. In the stage of plastic deformation, the use of the Hardening Soil model (HSM) more adequately describes the behavior of the soil, while the Mohr-Coulomb model (MCM) slightly overestimates the settlement. The distribution of settlements of the investigated object on strip foundations corresponds to the actual one recorded during long-term geodetic observations. The measured settlement of the foundations of the sections and those obtained by modeling have a satisfactory convergence. Scientific novelty. The correspondence of laboratory and field data and the results of modeling of soil-cement bases of strip foundations was checked. The practical significance. The models of soil behavior and the methods of specifying of soil-cement elements (SCE) for FEM modeling of reinforced soil bases of strip foundations have been tested.

Bearing capacity of shallow strip foundations on reinforced soil subjected to combined loading using upper bound theorem of finite element limit analysis and second-order cone programming

Bearing capacity of shallow strip foundations placed over both unreinforced and reinforced granular soils and subjected to combined loading is calculated by implementation of upper bound finite element limit analysis in conjunction with second-order cone programming technique. The soil mass is considered to be a granular medium reinforced with the inclusion of horizontal single and double layers of geogrid elements. To represent the impact of tensile resistance of reinforcement elements, an axillary variable is utilized to simulate the plastic energy dissipation of reinforcing elements without the application of any stress variables. General loading conditions are considered to profile the expansion of the failure envelopes in the V-H and V-M spaces for shallow strip foundations resting on reinforced soils. Results of this study are compared and validated against three different cases including the bearing capacity of shallow strip foundations subjected to vertical loading in the case of perfectly smooth and fully rough interfaces, limit load of shallow strip foundations subjected to combined loading, and vertical bearing capacity of shallow strip footings over a soil deposit reinforced with a single-layer of geosynthetic. Consistency of the results with those reported in the literature demonstrates the efficiency of proposed extended finite element upper bound formulations. The results are reported in the form of an efficiency factor which can be multiplied by the vertical bearing capacity of the shallow strip footing over unreinforced soil to find the ultimate bearing capacity of the reinforced foundation. The results show that the load inclination angle and eccentricity have significant impacts on the limit load and the optimum embedment depths of the reinforcement layer. It is further noted that the effect of reinforcement layer(s) in the improvement of bearing capacity in the V-M space is more pronounced than in the V-H space. The efficiency of reinforcement elements inclusion in improving the expanse of safe loading domain in the V-H and V-M spaces enhances with an increase in the soil internal friction angle.

Numerical Analysis for Estimating Penetration Depth by Ship-dragged Fluke Anchor

Anchor penetration by ship anchoring is emerging as a major risk factor for submarine cable. A numerical analysis method was established to predict the anchor penetration depth by ship-dragged fluke anchor in relation to setting the optimal burial depth of submarine cable. The soil resisting forces (bearing force, friction force) generated during the anchor penetration process were calculated for each of the fluke, shank and mooring chain of the anchor. The results of the numerical analysis were compared with the existing chart values of Vryhof (2015). It was found that it is desirable to use the force coefficients of strip foundation for the fluke and shank, and the force coefficients of a single vertical pile for mooring chain. The numerical analysis well reproduced the penetration trajectory in which the inclination angle of the lower surface of fluke gradually converged to zero.

Laboratory Study of the Behavior of Geogrid-Reinforced Strip Foundations with Inclined Loading

Laboratory Study of the Behavior of Geogrid-Reinforced Strip Foundations with Inclined Loading

Sensitivity modelling with objective damage assessment of unreinforced masonry façades undergoing different subsidence settlement patterns

This study aims to investigate the damage response of unreinforced masonry (URM) façades resting on strip foundations and subjected to ground settlements via numerical models. The models depict the non-linear constitutive behaviour of both the masonry, via smeared cracking, and of the soil-foundation interaction, via nonlinear interface elements. The influence of building features, such as the masonry material, the length over height (L/H) ratio of the geometry, the wall thickness, the number and size of openings and different types of strip foundations (i.e. reinforced concrete and unreinforced) is examined. A sensitivity study additionally investigates the influence of the interface stiffness and its constitutive model. A Gaussian curve is used to replicate the shape of the ground settlements; These simulate the loss of support underneath the foundation due to urban subsidence. Eight settlement shapes are applied in the FE models, including both symmetric and asymmetric profiles, while the angular distortion is used to measure their intensity. A new aspect is that the extent of the induced damage to the façade is assessed objectively using a damage parameter that represents the number, length and width of cracks in a single scalar value. The method distinguishes between the applied settlement profile at the bottom of the interface and the retrieved settlement profile measured on the façade. The analyses indicate that for a value of the angular distortion equal to 2 ‰ (or 1/500), computed from the resulting deformations of the façades, 60% of the models exhibit serviceability damage associated with cracks of about 5 mm width. Accordingly, the limit values available in the literature are observed to be too optimistic and not conservative in relation to the analyses presented in this study. A key outcome is that facades with an L/H smaller or equal to 1 do not exhibit cracks wider than 1 mm. Façades on reinforced concrete foundations were observed to be less susceptible to settlement damage, compared to unreinforced ones.

Seismic bearing capacity of shallow foundations subjected to inclined and eccentric loading using modified pseudo-dynamic method

In this paper, a comprehensive parametric study is conducted to evaluate the seismic bearing capacity of shallow strip foundations overlying dry and cohesionless granular soil under the actions of inclined and eccentric loadings. For this purpose, a systematic combination of the lower-bound theorems of the limit analysis, the finite element method, and the nonlinear programming is implemented. The seismic loading condition is simulated by the well-established modified pseudo-dynamic (MPD) approach by accounting for the significant influence of phase difference as well as the primary and shear waves propagation through applying non-uniform inertia forces along the vertical and horizontal directions, respectively. Unlike the pseudo-static approach, in the so-called modified pseudo-dynamic loading, a more realistic dynamic nature of the seismic excitation is taken into account using various soil dynamic properties and spectral parameters of the problem under study. In this way, a more viable response of the shallow foundation subjected to seismic loading could be captured by simulating a visco-elastic material through the well-defined Kelvin-Voigt model. The modified pseudo-dynamic (MPD) method considers the influences of shear and primary wave velocities, amplification of earthquake loading, and period of lateral shaking. The current MPD approach is capable of considering the local site effects and damping characteristics of the soil deposit underneath shallow footing by adopting a non-uniform and nonlinear acceleration field inside the soil medium. The results of the seismic bearing capacity are presented in the forms of spectral responses and failure envelopes for the eccentric and inclined loadings. The results show that the failure envelopes of the shallow foundation subjected to either inclined or eccentric loading significantly shrink with the increase in the earthquake accelerations and decrease in the material damping of the underlying soil mass. The amount of changes in the size of failure envelopes in the normalized V-H and V-M spaces due to the variation of seismic intensity and material damping depends directly on the non-dimensional frequency of the earthquake excitation.