Numerical study of the soil–structure interaction within mining subsidence areas

Structures affected by mining subsidence are exposed to heavy damage potential in relation to the induced tensile or compressive horizontal ground strains. This study intends to specify and compare the mining subsidence effect in terms of building transmitted movements or induced stresses, given the soil–structure interaction phenomena produced at the interface between a “stiff” elastic structure and a “flexible” elastoplastic soil.     

Computational simulation of time-dependent behavior of soil–structure interaction by using a novel creep model: Application to a geosynthetic-reinforced soil physical model

In this paper, a model geosynthetic-reinforced soil retaining walls (GRS-RW) is tested by vertically loading it through a rough footing on the top near the retaining wall and the results are simulated by a sophisticated nonlinear Finite Element Method (FEM) having a novel rate dependent constitutive model for both the backfill material and the geosynthetic reinforcement. Usually, polymer geosynthetic reinforcement is known to exhibit more-or-less rate-dependent stress–strain or load–strain behavior due to their viscous properties. The geomaterials (i.e., clay, sand, gravel and soft rock) also exhibit viscous properties. The viscous behavior of geometrials are quite different from that of the polymer based geosynthetic-reinforcements. It has been revealed recently that viscous behavior of sand is a kind of temporary effect, which vanishes with time. So the rate-dependent deformation of backfill reinforced with polymer geosynthetic reinforcement becomes highly complicated due to interactions between the elasto-viscoplastic properties of backfill and reinforcement. In the present study, a scaled model geosynthetic-reinforced soil retaining wall is tested with a vertically loaded rough rigid footing. The results of the model test are simulated by using an appropriate elasto-viscoplastic constitutive model of both sand and geogrid embedded in a nonlinear plane strain FEM.     

Effect of the soil–pile–structure interaction in seismic analysis: case of liquefiable soils

The design of earthquake-resistant structures depends greatly on the soil–foundation–structure interaction. This interaction is more complex in the presence of liquefiable soils. Pile and rigid inclusion systems represent a useful practice to support structures in the presence of liquefiable soils in seismic zones. Both systems increase the bearing capacity of soil and allow reducing the settlements in the structure. Numerical models with a 3-storey reinforced concrete frame founded on inclusions systems (soil–inclusion–platform–structure) and pile systems (soil–pile–structure) were analyzed. Finite difference numerical models were developed using Flac 3D. Two different soil profiles were considered. A simple constitutive model for liquefaction analysis that relates the volumetric strain increment to the cyclic shear strain amplitude was utilized to represent the behavior of the sand, and the linear elastic perfectly plastic constitutive model with a Mohr–Coulomb failure criterion was used to represent the behavior of the earth platform. Two earthquakes were used to study the influence of the different frequency of excitation in the systems. The results were presented in terms of maximum shear forces distribution in the superstructure and spectrum response of each system. The efforts and displacements in the rigid elements (piles or rigid inclusions) were compared for the different systems. The bending and buckling failure modes of the pile were examined. The results show that the pile system, the soil profile and the frequency of excitation have a great influence on the magnitude and location of efforts and displacements in the rigid elements.

     

Non-linear soil–structure interaction in disconnected piled raft foundations

Disconnected piled raft foundations are characterised by no structural connection between the upper raft and the underlying piles, mostly playing the role of settlement-reducers. The resulting raft–pile gap is usually filled with a granular interlayer, through which the loads from the superstructure are transferred to the piles.In this paper, the complex interaction mechanisms involving the foundational components (raft, piles and soil) are numerically investigated by means of 3D finite elements analyses, accounting for soil non-linearity. The main features of the soil–structure interaction mechanisms under purely vertical external loads are explored over a realistic range of raft–soil gaps for different pile configurations, in which the number of piles – i.e. their spacing – is varied. Special attention is also devoted to the structural response of the piles in terms of axial and bending internal stress resultants. In particular, while disconnection beneficially affects the structural pile response, increasing the raft–pile gap tends to reduce the overall settlement/stiffness efficiencies.The numerical results being presented are in substantial agreement with the outcomes from literature small-scale experiments and suggest a number of relevant theoretical inferences.     

Three dimensional Finite Element modeling of seismic soil–structure interaction in soft soil

Earthquakes in regions underlain by soft clay have amply demonstrated the detrimental effects of soil–structure interaction (SSI) in such settings. This paper describes a new three dimensional Finite Element model utilizing linear elastic single degree of freedom (SDOF) structure and a nonlinear elasto-plastic constitutive model for soil behavior in order to capture the nonlinear foundation–soil coupled response under seismic loadings. Results from an experimental SSI centrifuge test were used to verify the reliability of the numerical model followed by parametric studies to evaluate performance of linear elastic structures underlain by soft saturated clay. The results of parametric study demonstrate that rigid slender (tall) structures are highly susceptible to the SSI effects including alteration of natural frequency, foundation rocking and excessive base shear demand. Structure–foundation stiffness and aspect ratios were found to be crucial parameters controlling coupled foundation–structure performance in flexible-base structures. Furthermore, frequency content of input motion, site response and structure must be taken into account to avoid occurrence of resonance problem.     

On wave–current interaction by the Green–Naghdi equations in shallow water

This work is on the use of the Green–Naghdi (GN) nonlinear wave equations for simulating wave–current interaction in shallow water. The stream-function wave theory is used at the wave-maker boundary to generate nonlinear incident waves to consider the wave–current interaction. The nonlinear GN equations are solved in the time domain by use of the finite-difference method. The model is evaluated with data from three experimental studies. A strong opposing current over a submerged bar is investigated in the first test case. In the second test case, the interaction of waves with a uniform current over flat bottom is considered. In the third case, wave–current interaction over a variable bathymetry with the following and opposing currents is studied. The numerical results obtained by the GN equations are compared with the experimental data and results based on the Boussinesq equations. A good agreement is obtained for the three experimental studies considered for a wide range of wave and current conditions.     

An analytical model of soil–structure interaction with swelling soils during droughts

Lightly loaded structures constructed on expansive soils may develop structural damage as a result of changes in the soil’s moisture content. This study investigated an analytical model of soil–structure interaction to assess the settlement of dwellings built on swelling soils when droughts occur. The building behavior was investigated with the Euler–Bernoulli beam theory, and the ground behavior was investigated with a Winkler-derived model based on the state surface approach. The analytical model results were compared to those of a finite element analysis using the Barcelona Expansive Model (BExM) performed with Code_Bright.The analytical model was then used to assess the settlement transmission ratio for a typology of clayey soils and different parameters of building. The results indicated that the final deflection of the building increased with the building length and soil suction. The building deflection due to the suction variations was inversely proportional to the load, the rigidity of the building and the embedding depth of the foundation. Increasing these parameters made the building less vulnerable to shrinkage and swelling action.     

GPU-accelerated iterative solutions for finite element analysis of soil–structure interaction problems

Soil–structure interaction problems are commonly encountered in engineering practice, and the resulting linear systems of equations are difficult to solve due to the significant material stiffness contrast. In this study, a novel partitioned block preconditioner in conjunction with the Krylov subspace iterative method symmetric quasiminimal residual is proposed to solve such linear equations. The performance of these investigated preconditioners is evaluated and compared on both the CPU architecture and the hybrid CPU–graphics processing units (GPU) computing environment. On the hybrid CPU–GPU computing platform, the capability of GPU in parallel implementation and high-intensity floating point operations is exploited to accelerate the iterative solutions, and particular attention is paid to the matrix–vector multiplications involved in the iterative process. Based on a pile-group foundation example and a tunneling example, numerical results show that the partitioned block preconditioners investigated are very efficient for the soil–structure interaction problems. However, their comparative performances may apparently depend on the computer architecture. When the CPU computer architecture is used, the novel partitioned block symmetric successive over-relaxation preconditioner appears to be the most efficient, but when the hybrid CPU–GPU computer architecture is adopted, it is shown that the inexact block diagonal preconditioners embedded with simple diagonal approximation to the soil block outperform the others.     

A 2.5-D coupled FE–BE model for the dynamic interaction between saturated soil and longitudinally invariant structures

A two-and-a-half-dimensional (2.5-D) coupled finite element–boundary element (FE–BE) model is presented to simulate the three-dimensional dynamic interaction between saturated soils and structures with longitudinally invariant geometries. A regularized 2.5-D boundary integral equation for saturated porous media is derived that avoids the evaluation of singular traction integrals. The 2.5-D coupled FE–BE model is established by using the continuity conditions on the soil–structure interface. The developed model is verified through comparison with an existing semi-analytical method. Two case studies of a tunnel embedded in a poroelastic half-space and the efficiency of a vibration isolating screen are presented.     

Crustal structure of the Alpine–Pannonian transition zone: a combined seismic and gravity study

 The crustal structure of the transition zone between the Eastern Alps and the western part of the Pannonian depression (Danube basin) is traditionally interpreted in terms of subvertical Tertiary strike-slip and normal faults separating different Alpine tectonic units. Reevaluation of approximately 4000-km-long hydrocarbon exploration reflection seismic sections and a few deep seismic profiles, together with data from approximately 300 wells, suggests a different structural model. It implies that extensional collapse of the Alpine orogene in the Middle Miocene was controlled by listric normal faults, which usually crosscut Alpine nappes at shallow levels, but at depth merge with overthrust planes separating the different Alpine units. The alternative structural model was tested along a transect across the Danube basin by gravity model calculations, and the results show that the model of low-angle extensional faulting is indeed viable. Regarding the whole lithosphere of the western Pannonian basin, gravity modelling indicates a remarkable asymmetry in the thickness minima of the attenuated crust and upper mantle. The approximately 160 km lateral offset between the two minima suggests that during the Miocene extension of the Pannonian basin detachment of the upper crust from the mantle lithosphere took place along a rheologically weak lower crust. Received: 13 July 1998 / Accepted: 18 March 1999     

Geotechnical zonation and soil–structure interaction at Puerto Vallarta,México

Natural Hazards - We performed a seismic vulnerability assessment that involves geotechnical and building structure analysis for Puerto Vallarta, Mexico, a city located along the pacific coast....     

Experimental investigations on ultimate bearing capacity of peat stabilized by a group of soil–cement column: a comparative study

The aim of this paper was to determine the ultimate vertical bearing capacity of rectangular rigid footings resting on homogeneous peat stabilized by a group of cement deep mixing (CDM) columns. For this purpose, a series of physical modeling tests involving end-bearing and floating CDM columns were performed. Three length/depth ratios of 0.25, 0.5, and 0.75 and three area improvement ratios of 13.1, 19.6, and 26.2 % were considered. Bearing capacity of the footings was studied using different analytical procedures. The results indicated that compared to unimproved peat, the average ultimate bearing capacity (UBC) improvement of floating and end-bearing CDM columns were 60 and 223 %, respectively. The current study found that simple Brom’s method predicted the UBC of the peat stabilized with floating CDM columns with reasonable accuracy, but underestimated the UBC by up to 25 % in the case of end-bearing CDM columns. Published laboratory experiences of stabilizing soft soils using soil–cement columns were also collated in this paper.     

Laboratory investigation of erosion behavior at the soil–structure interface affected by various structural factors

Natural Hazards - Being regarded as an elementary contact unit in the foundation and embankment of levees, trenches and other engineering constructions, the soil–structure interface is highly...     

Numerical modeling of soil–structure interface of a concrete-faced rockfill dam

Concrete-faced rockfill dams (CFRD) are widely used in large-scale hydraulic projects. The face slab, the key seepage-proof structure of great concern, has a strong interaction with the neighboring gravel cushion layer due to a significant difference in their stiffness. An elasto-plasticity damage interface element, a numerical format of the EPDI model, is described for numerical analysis of a CFRD that can trace the separation and re-contact between the face slab and the cushion layer at the interface. As verified by simulating slide block and direct shear interface tests, this element was confirmed to capture effectively the primary monotonic and cyclic behaviors of the interface. This element can easily be extended to the finite element method (FEM) programs that involve the Goodman interface element. The analysis of a typical CFRD showed that the interface model describes a significant effect on the stress response of the face slab under different conditions, including dam construction, water storage, and earthquake. Treatments of the cushion layer, such as an asphalt layer, changed the behavior of the interface between it and the face slab, which resulted in a significant effect on the stress response of the face slab. The top of the face slab exhibited a significant separation from the cushion layer during construction, induced mainly by construction of the neighboring dam body.     

Enhancement of a hypoplastic model for granular soil–structure interface behaviour

Modelling of interfaces in geotechnical engineering is an important issue. Interfaces between structural elements (e.g., anchors, piles, tunnel linings) and soils are widely used in geotechnical engineering. The objective of this article is to propose an enhanced hypoplastic interface model that incorporates the in-plane stresses at the interface. To this aim, we develop a general approach to convert the existing hypoplastic model with a predefined limit state surface for sands into an interface model. This is achieved by adopting reduced stress and stretching vectors and redefining tensorial operations which can be used in the existing continuum model with few modifications. The enhanced interface model and the previous model are compared under constant-load, stiffness and volume conditions. The comparison is followed by a verification of two the approaches for modelling the different surface roughness. Subsequently, a validation between available experimental data from the literature versus simulations is presented. The new enhanced model gives improved predictions by the incorporation of in-plane stresses into the model formulation.     

A nonlinear HHT-α method with elastic–plastic soil–structure interaction in a coupled SBFEM/FEM approach

This article presents a new method for the calculation of elastic–plastic building ground deformations and elastic–plastic building ground failure including wave propagation in the ground. The presented procedure is a hybrid method, based on several common calculation methods. Included is a nonlinear calculation with the finite element method (FEM), a nonlinear HHT-alpha method with full Newton–Raphson iteration and the scaled boundary finite element method (SBFEM). The presented method can be used as a tool for the accurate calculation of building ground deformations and the stability of the subsoil with included dynamic loading.     

Experimental study on the electrical resistivity of soil–cement admixtures

Recently in China, soil–cement is widely used to improve the soft ground in the highway construction engineering. Literature studies are mainly investigating the mechanical properties of the soil–cement, while its properties of the electrical resistivity are not well addressed. In this paper, the properties of the electrical resistivity of the reconstituted soil-cement and the in situ soil–cement columns are investigated. The test results show that the electrical resistivity of the soil–cement increases with the increase in the cement-mixing ratio and curing time, whereas it decreases with the increase in the water content, degree of saturation and water–cement ratio. A simple equation is proposed to predict the electrical resistivity of soil–cement under the condition of the specified curing time and water–cement ratio. It is found that the electrical resistivity has a good relationship with the unconfined compression strength and blow count of SPT. It is expected that the electrical resistivity method can be widely used for checking/controlling the quality of soil–cement in practice.