On the resonance effect by dynamic soil–structure interaction: a revelation study

The present study makes an attempt to investigate the soil–structure resonance effects on a structure based on dynamic soil–structure interaction (SSI) methodology by direct method configuration using 2D finite element method (FEM). The investigation has been focused on the numerical application for the four soil–structure models particularly adjusted to be in resonance. These models have been established by single homogenous soil layers with alternating thicknesses of 0, 25, 50, 75 m and shear wave velocities of 300, 600, 900 m/s-a midrise reinforced concrete structure with a six-story and a three-bay that rests on the ground surface with the corresponding width of 1,400 m. The substructure has been modeled by plane strain. A common strong ground motion record, 1940 El Centro Earthquake, has been used as the dynamic excitation of time history analysis, and the amplitudes, shear forces and moments affecting on the structure have been computed under resonance. The applicability and accuracy of the FEM modeling to the fundamental period of soils have been confirmed by the site response analysis of SHAKE. The results indicate that the resonance effect on the structure becomes prominent by soil amplification with the increased soil layer thickness. Even though the soil layer has good engineering characteristics, the ground story of the structure under resonance is found to suffer from the larger soil layer thicknesses. The rate of increment in shear forces is more pronounced on midstory of the structure, which may contribute to the explanation of the heavily damage on the midrise buildings subjected to earthquake. Presumably, the estimated moment ratios could represent the factor of safeties that are excessively high due to the resonance condition. The findings obtained in this study clearly demonstrate the importance of the resonance effect of SSI on the structure and can be beneficial for gaining an insight into code provisions against resonance.     

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.     

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.     

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.

     

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 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.     

Numerical simulation of flow processes in liquefied soils using a soil–water-coupled smoothed particle hydrodynamics method

Liquefaction can result in the damage or collapse of structures during an earthquake and can therefore be a great threat to life and property. Many site investigations of liquefaction disasters are needed to study the large-scale deformation and flow mechanisms of liquefied soils that can be used for performance assessments and infrastructure improvement. To overcome the disadvantages of traditional flow analysis methods for liquefied soils, a soil–water-coupled smoothed particle hydrodynamics (SPH) modeling method was developed to analyze flow in liquefied soils. In the proposed SPH method, water and soil were simulated as different layers, while permeability, porosity, and interaction forces could be combined to model water-saturated porous media. A simple shear test was simulated using the SPH method with an elastic model to verify its application to solid phase materials. Subsequently, the applicability of the proposed SPH modeling method to the simulation of interaction forces between water and soil was verified by a falling-head permeability test. The coupled SPH method produced good simulations for both the simple shear and falling-head permeability tests. Using a fit-for-purpose experimental apparatus, a physical flow model test of liquefied sand has been designed and conducted. To complement the physical test, a numerical simulation has been undertaken based on the soil–water-coupled SPH method. The numerical results correspond well with the physical model test results in observed configurations and velocity vectors. An embankment failure in northern Sweden was selected so that the application of the soil–water-coupled SPH method could be extended to an actual example of liquefaction. The coupled SPH method simulated the embankment failure with the site investigation well. They have also estimated horizontal displacements and velocities, which can be used to greatly improve the seismic safety of structures.     

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.     

SPH model for fluid–structure interaction and its application to debris flow impact estimation

On 13 August 2010, significant debris flows were triggered by intense rainfall events in Wenchuan earthquake-affected areas, destroying numerous houses, bridges, and traffic facilities. To investigate the impact force of debris flows, a fluid–structure coupled numerical model based on smoothed particle hydrodynamics is established in this work. The debris flow material is modeled as a viscous fluid, and the check dams are simulated as elastic solid (note that only the maximum impact forces are evaluated in this work). The governing equations of both phases are solved respectively, and their interaction is calculated. We validate the model with the simulation of a sand flow model test and confirm its ability to calculate the impact force. The Wenjia gully and Hongchun gully debris flows are simulated as the application of the coupled smoothed particle hydrodynamic model. The propagation of the debris flows is then predicted, and we obtain the evolution of the impact forces on the check dams.     

Influence of model type,bias and input parameter variability on reliability analysis for simple limit states in soil–structure interaction problems

ABSTRACT

A general closed-form solution for the true probability of failure of a simple limit state function with one load term and one resistance term is derived. The formulation considers contributions due to model type, uncertainty in method bias values, bias dependencies, uncertainty in estimates of nominal values for correlated and uncorrelated load and resistance terms, and average margin of safety expressed as the operational factor of safety. Example calculations are presented using different load and resistance models for the pullout internal stability limit state of steel strip reinforced soil walls together with matching bias data reported in the literature.     

Application of spectrum–area fractal model to identify of geochemical anomalies based on soil data in Kahang porphyry-type Cu deposit,Iran

The aim of this study is to identify geochemical anomalies using power spectrum–area (S–A) method based on the grade values of Cu, Mo and Au in 2709 soil samples collected from Kahang porphyry-type Cu deposit, Central Iran. S–A log–log plots indicated that there are three stages of Cu, Mo and Au enrichment. The third enrichment was considered as the main stage for the presence of Cu, Mo and Au at the concentrations above 416 ppm, 23 ppm and 71 ppb, respectively. Elemental anomalies are positively associated with monzo–granite–diorite and breccias units which are in the central and western parts of the deposit. The anomalies are located within the potassic, phyllic and argillic alteration types and also there is the positive correlation between the anomalies and nearing faults in the studied area. The results obtained via fractal model were interpreted accordingly to incorporate the information for the mineralized areas including detailed geological map, structural analysis and alterations. The results show that S–A multifractal modeling is applicable for anomalies delineation based on soil data.     

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.     

Analysis of rainfall-induced infinite slope failure during typhoon using a hydrological–geotechnical model

Rainwater infiltration during typhoons tends to trigger slope instability. This paper presents the results of a study on slope response to rainwater infiltration during heavy rainfall in a mountain area of Taiwan. The Green-Ampt infiltration model is adopted here to study the behavior of rainwater infiltration on slopes. The failure mechanism of infinite slope is chosen to represent the rainfall-induced shallow slope failure. By combining rain infiltration model and infinite slope analysis, the proposed model can estimate the occurrence time of a slope failure. In general, if a slope failure is to happen on a slope covered with low permeability soil, failure tends to happen after the occurrence of the maximum rainfall intensity. In contrast, slope failure tends to occur prior to the occurrence of maximum rainfall intensity if a slope is covered with high-permeability soil. To predict the potential and timing of a landslide, a method is proposed here based on the normalized rainfall intensity (NRI) and normalized accumulated rainfall (NAR). If the actual NAR is higher than the NAR calculated by the proposed method, slope failure is very likely to happen. Otherwise, the slope is unlikely to fail. The applicability of the proposed model to occurrence time and the NAR–NRI relationship is evaluated using landslide cases obtained from the literature. The results of the proposed method are close to that of the selected cases. It verifies the applicability of the proposed method to slopes in different areas of the world. An erratum to this article can be found at     

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.     

Formation of the Olyutorsky–Kamchatka foldbelt: a kinematic model

The Olyutorsky–Kamchatka foldbelt formed as a result of two successive collisions of the Achaivayam–Valaginsky and Kronotsky–Commander island arcs with the Eurasian margin where the two terranes docked after a long NW transport. We model their motion history from the Middle Campanian to Present and illustrate the respective plate margin evolution with ten reconstructions. In this modeling the arcs are assumed to travel on the periphery of the large plates of Eurasia, North America, Pacific, and Kula, for which the velocities and directions of motion are known from published data. The model predicts that the Achaivayam–Valaginsky arc was the leading edge of the Kula plate from the Middle Campanian to the Middle Paleocene and then moved slowly with the Pacific plate as long as the Middle Eocene when it accreted to Eurasia. The Kronotsky arc initiated in the Middle Campanian on the margin of North America and was its part till the latest Paleocene when the terrane changed polarity to move northwestward with the Pacific plate and eventually to collide with Eurasia in the Late Miocene. The predicted paleolatitudes of the Achaivayam–Valaginsky and Kronotsky–Commander island arcs for the latest Cretaceous and Paleogene are consistent with nine (out of eleven) reliable paleomagnetic determinations for samples from the two arcs. Additional changes imposed on the initial model parameters (kinematics of the large plates, relative position of the Kula–Pacific Ridge and the Emperor seamount chain, or time of active volcanism within the arcs) worsen the fit of the final reconstructions to available geological and paleomagnetic data. Therefore, the suggested model appears to be the most consistent one at this stage of knowledge.     

Pullout behavior of biocement–geosynthetic reinforcement system: a parametric study

Acta Geotechnica - In the biocement–geosynthetic system, biocement is combined with geosynthetic to increase the pullout resistance of the geosynthetic and thereby the stability of reinforced...