Generalized solution to Coulomb’s seismic active earth pressure acting on rigid retaining wall with cohesive backfill and trial application for evaluation of seismic performance of retaining wall

In this paper, a general solution for evaluating the Coulomb-type seismic active earth pressure that acts on a rigid retaining wall from the cohesive backfill soil is shown together with its derivation process. In the proposed solution, the mobilization of the cohesion on the failure plane in the backfill soil of the retaining wall and the associated increase in shear strength are considered in the pseudo-static limit equilibrium approach under the assumption that the cohesion is uniformly distributed in the backfill soil. The angle of the failure plane and the seismic active earth pressure calculated by the proposed equation completely agree with the calculation results by the trial wedge method, which shows the validity of the proposed solution. In addition, by combining the concept of the Modified Mononobe-Okabe method and the proposed equation, a calculation method for the seismic active earth pressure is proposed. It can consider the effect of backfill cohesion and can be applied even under a large seismic load. Furthermore, a series of trial analyses on the effect of backfill cohesion on the seismic performance of the retaining wall is also conducted using the proposed equation. A series of analyses using the case of a retaining wall damaged during the 1995 Hyogo-ken Nanbu earthquake shows that the effect of backfill cohesion is significant in the seismic performance evaluation and the design of aseismic reinforcements.     

Seismic stability analysis of gravity retaining wall supporting c–φ soil with cracks

This article presents an analytical approach for the seismic stability analysis of gravity retaining wall with c–φ backfill soil. Cracks which are pre-existing (open before the collapse) and are form as part of slope collapse are considered. For a translational failure mechanism assumed, formulas are provided to calculate directly the yield acceleration and the inclination of failure surface. Factors such as cracks and cracks opening, wall back inclination, soil-wall friction, backfill slope are easily to be coupled into the formulations. Both the depth and most adverse location of the crack can be determined from the optimization procedure. Comparisons are made with existing methods and the influences of cracks opening are discussed. The influence of a crack presence on seismic stability of soil-wall system is distinct and pre-existing (opened) cracks have more adverse effect.     

Estimating Undrained Shear Strength of Soft Clay Ground Improved by Pre-Loading with PVD — Case History in Bangkok—

The installment of pre-fabricated vertical drain (PVD) combined with pre-loading is an efficient way to gain the prescribed strength and compressibility of very soft clay over a short period of time. This note describes case histories of such improvement performed in Bangkok. The change in undrained shear strength, s_u, before and after the ground improvement was investigated at two sites in Bangkok area by means of field vane test (FVT) and flat dilatometer test (DMT). The results of FVT showed that the s_u value of soft Bangkok clay increased over nearly the full depth down to the tip of the PVDs. It is also demonstrated that DMT may be a useful tool for promptly assessing the change of s_u in soft clay due to pre-loading. Applicability of the SHANSEP method in estimating the profile of s_u with depth in recently overconsolidated clay ground after pre-loading is also discussed.     

Corridor wall linings— Effect on fire performance

During December 1964 and January 1965, research was conducted to determine the effects of three types of wall linings on fire performance within a partially ventilated corridor. Temperature and light transmission data were recorded, and gas samples were collected for immediate and later analysis. This information was supplemented by the recorded comments of observers, stationed in rooms adjacent to the corridor during the tests. Note: Based on the report “Effect of Wall Linings on the Fire Performance Within a Partially Ventilated Corridor” by Messrs. Schaffer and Eickner, publisherd by the Forest Products Laboratory, Madison, Wisconsin, 53705, in cooperation with the American Hardboard Association.     

Pesticide‐microbial interaction in the soil

Soils collected from the Gezira irrigation scheme in Sudan were incubated with five pesticides (pyrolan, α‐and β‐endosulphan, γ‐HCH and dieldrin), using three independent methods (incubation of microbial culture with soil and leachates, with carbon‐based growth media and with carbon‐free mineral salt agar). Endosulphan isomers were degraded by soil micro‐organisms to a much greater extent than pyrolan, dieldrin or γ‐HCH. When applied at low concentration (280 ppm), α‐endosulphan was broken down by both bacteria and fungi; whereas, β‐endosulphan was degraded mostly by bacteria and dieldrin was utilized by fungi. However, at high concentration (4000 ppm), γ‐HCH increased the growth of micro‐organisms (gram positive bacilli); but at this high concentration, the other pesticides inhibited all micro‐organisms in the Gezira soil.     

Back Analysis of Reclamation by Pump-Dredged Marine Clay—Influence of Ground Water Lowering—

When pump-dredged clays are discharged into a pond, suspended soil particles settle loosely to create sediments, which subsequently consolidate due to their own weight over a long period of time. In planning the capacity of such a disposal pond, it is important to estimate the time dependent volume change of dredged clays during the reclamation process. As the land thus created is extremely soft, ground improvement work is necessary if there exists a further plan of utilising the land. Predicting the soil profile of reclaimed land is absolutely necessary for designing the ground improvement. In this paper the authors i) outline the 18-year reclamation history of the Kanda Disposal Pond, ii) introduce a program to analyse self-weight consolidation under fully submerged condition, iii) modify the program to represent the suction effect due to ground water lowering, and iv) verify the applicability of the modified program by comparing the calculated results with the measured data.A simple analysis under fully submerged condition cannot explain the record of an 18-year reclamation, even if various combinations of consolidation parameters are used. The code modified to include the suction effect successfully simulates the actual behaviour when the appropriate parameters concerning the suction are chosen.     

Local–global mode interaction in stringer-stiffened plates

A recently developed nonlinear analytical model for axially loaded thin-walled stringer-stiffened plates based on variational principles is extended to include local buckling of the main plate. Interaction between the weakly stable global buckling mode and the strongly stable local buckling mode is highlighted. Highly unstable post-buckling behaviour and a progressively changing wavelength in the local buckling mode profile are observed under increasing compressive deformation. The analytical model is compared against both physical experiments from the literature and finite element analysis conducted in the commercial code Abaqus; excellent agreement is found both in terms of the mechanical response and the predicted deflections.     

“Third places” and social interaction in deprived neighbourhoods in Great Britain

This paper explores social interaction in local ‘public’ social spaces such as local shops, pubs, cafés, and community centres in deprived neighbourhoods. More specifically, it examines the importance, role and function of these places, which have been described by Oldenberg and Brissett (Qual Sociol 5(4):265–284, 1982), Oldenburg (Urban design reader. Architectural Place, Oxford, 2007) as being “third places” of social interaction after the home (first) and workplace (second). It does so by drawing on data gleaned from in-depth interviews with 180 residents in six deprived areas neighbourhoods across Great Britain, conducted as part of a study of the links between poverty and place funded by the Joseph Rowntree Foundation. The paper notes that local third places are an important medium for social interaction in these areas, although their importance appears to vary by population group. It notes that shops appear to be a particularly important social space. It also identifies some of the barriers to social interaction within third places and concludes by highlighting some of the key implications for policy to emerge from the research.     

Axial–flexural interaction in circular FRP-confined reinforced concrete columns

External confinement by fibre reinforced polymers (FRPs) is now a widely implemented technique to strengthen reinforced concrete (RC) columns. To date, the vast majority of experiments on FRP-confined concrete have considered short, unreinforced, small scale concrete cylinders, with aspect ratios of less than three and tested under concentric axial load. In practice, RC columns invariably have aspect ratios larger than three and are subjected to inadvertent load eccentricities or combined axial–flexural (P–M) loading. Limited available research suggests that the effectiveness of FRP confinement is reduced under P–M loading. This paper presents the results of a systematic test program on circular FRP-confined RC columns of realistic slenderness under eccentric axial loads to study the mechanics and performance of these types of members. Test data are compared against theoretical P–M interaction diagrams, as well as against recently published design guidelines for P–M interaction in FRP-confined RC columns.     

Influence of soil——structure interaction on seismic collapse resistance of super-tall buildings

Numerous field tests indicate that the soilestructure interaction(SSI) has a significant impact on the dynamic characteristics of super-tall buildings,which may lead to unexpected structural seismic responses and/or failure.Taking the Shanghai Tower with a total height of 632 m as the research object,the substructure approach is used to simulate the SSI effect on the seismic responses of Shanghai Tower.The refined finite element(FE) model of the superstructure of Shanghai Tower and the simplified analytical model of the foundation and adjacent soil are established.Subsequently,the collapse process of Shanghai Tower taking into account the SSI is predicted,as well as its final collapse mechanism.The influences of the SSI on the collapse resistance capacity and failure sequences are discussed.The results indicate that,when considering the SSI,the fundamental period of Shanghai Tower has been extended significantly,and the collapse margin ratio has been improved,with a corresponding decrease of the seismic demand.In addition,the SSI has some impact on the failure sequences of Shanghai Tower subjected to extreme earthquakes,but a negligible impact on the final failure modes.     

Simulation of particle deposition in ventilation duct with a particle–wall impact model

Particle deposition velocities and locations in horizontal ventilation ducts are investigated by incorporating the effect of particle–wall collision. Particle deposition onto two types of surfaces, stainless steel surface and tedlar surface, are simulated and compared. The RNG k–? model is employed to predict the air turbulence, and the Lagrangian particle tracking method integrated with particle–wall impact model is used to reveal particle physical behaviors. Turbulent dispersion of the particles is taken into account by adopting the discrete random walk (DRW) model. Particle deposition velocities and distributions onto the wall, ceiling and floor are simulated and analyzed. For both stainless steel and tedlar ducts, reasonable agreements are achieved between the simulation data and experimental data for particles with larger relaxation time. Particle deposition velocity is related to particle relaxation time and surface materials. The particle–wall impact model affects the prediction of deposition velocity and distribution. As the effects of Brownian diffusion and turbulent fluctuation on particle deposition are not considered, the presented model applies better to the particles with relatively large relaxation time.     

Challenges of forest landscape modeling—Simulating large landscapes and validating results

Over the last 20 years, we have seen a rapid development in the field of forest landscape modeling, fueled by both technological and theoretical advances. Two fundamental challenges have persisted since the inception of FLMs: (1) balancing realistic simulation of ecological processes at broad spatial and temporal scales with computing capacity, and (2) validating modeled results using independent, spatially explicit time series data. The paper discusses the current status and future directions regarding these two challenges.     

Towards an integrated European Research Area? Findings from Eigenvector spatially filtered spatial interaction models using European Framework Programme data*

One of the main goals of the European Research Area (ERA) concept is to improve integration of the European research system. The main policy instrument in this context is the European Framework Programme (FP) supporting pre‐competitive collaborative Research and Development (R&D). The objective of this study is to monitor progress towards ERA by identifying the evolution of separation effects influencing FP collaboration intensities between 255 European regions over the period 1999–2006. We employ spatial interaction models accounting for spatial autocorrelation by using spatial filtering methods. The results show that geographical distance and country border effects gradually decrease, and point to the contribution of the FPs to the realization of ERA.     

Axisymmetric alternating direction explicit scheme for efficient coupled simulation of hydro-mechanical interaction in geotechnical engineering—Application to circular footing and deep tunnel in saturated ground

Explicit solution techniques have been widely used in geotechnical engineering for simulating the coupled hydro-mechanical (H-M) interaction of fluid flow and deformation induced by structures built above and under saturated ground, i.e. circular footing and deep tunnel. However, the technique is only conditionally stable and requires small time steps, portending its inefficiency for simulating large-scale H-M problems. To improve its efficiency, the unconditionally stable alternating direction explicit (ADE) scheme could be used to solve the flow problem. The standard ADE scheme, however, is only moderately accurate and is restricted to uniform grids and plane strain flow conditions. This paper aims to remove these drawbacks by developing a novel high-order ADE scheme capable of solving flow problems in non-uniform grids and under axisymmetric conditions. The new scheme is derived by performing a fourth-order finite difference (FD) approximation to the spatial derivatives of the axisymmetric fluid–diffusion equation in a non-uniform grid configuration. The implicit Crank-Nicolson technique is then applied to the resulting approximation, and the subsequent equation is split into two alternating direction sweeps, giving rise to a new axisymmetric ADE scheme. The pore pressure solutions from the new scheme are then sequentially coupled with an existing geomechanical simulator in the computer code fast Lagrangian analysis of continua (FLAC). This coupling procedure is called the sequentially-explicit coupling technique based on the fourth-order axisymmetric ADE scheme or SEA-4-AXI. Application of SEA-4-AXI for solving axisymmetric consolidation of a circular footing and of advancing tunnel in deep saturated ground shows that SEA-4-AXI reduces computer runtime up to 42%–50% that of FLAC's basic scheme without numerical instability. In addition, it produces high numerical accuracy of the H-M solutions with average percentage difference of only 0.5%–1.8%.     

The use of state-of-the-art transport models by policymakers – beauty in simplicity?

Transport demand models have a long history of being a major tool in transport policy making. However, whether they are truly used in decision-making processes, and if so, whether the knowledge they provide is actually understood, is questionable. The potential contribution they can make and the importance of such models is not disputed; however, evidence shows that many issues arise with their actual use that severely limits their potential contribution. Based on case study methodology and analysis of the use of models in the transport policy processes in two countries, the UK and Israel, this paper aims to provide empirical evidence of the issues contributing to limiting the potential contribution of models and to make recommendations for better utilisation of the knowledge they can produce. The main conclusion reached is that transport models must be made simpler if they are to contribute more than they currently do to decision-making in transport policy and planning.     

Evaluation of landslide analyzing models in weak rocks—case study: Abnahr damsite,Kohgilouyeh and Booyer Ahamd Province,Iran

The right abutment of Abnahr dam consists of Cretaceous marl and some marly limestone that are highly fractured due to tectonic stresses. Low strength and highly fractured structure of the rocks result in fragmentation during drilling by the rock sampling tools. However, this material is still too strong for conventional soil sampling methods. The types of marl are similar to rock material in natural landscapes but drilled material has soil-like behavior. This paper evaluates the behavior of this material in slope stability problems that concern the right abutment of Abnahr dam in existing conditions. For attaining reliable answers to this problem, several undisturbed samples were provided with assistance of the experienced experts and using specific methods. As these samples were rather soils, they were tested by various soil tests such as three-dimensional tests. Moreover some samples were gathered by hand-operated methods including test pits. In order to gain information about the rock parameters, several rock tests were performed. In the next stage, by use of the results of laboratory tests and field observations, slope stability analyses were performed on several models of right abutment of the dam. Lastly, a comparison between different analysis methods of the performed models on right abutment under virtual loads led to important conclusions.     

Practical need of scientific material models for structural fire design — General review

More and more countries are now permitting a classification of structural elements with respect to fire exposure to be formulated analytically as an alternative to the internationally prevalent method of classification, based on results of standard fire resistance tests. In some countries, the authorities also have taken the next step to approve a general practical application of a direct analytical design procedure, based on the natural compartment fire concept.The process of an analytical structural fire design comprises three main components — the determination of the fire exposure, the thermal analysis and the mechanical behaviour analysis. The components require access to well-defined input information on: (a) material properties for describing the characteristics of the fire load and the compartment fire; (b) material properties for determining the transient temperature state of the fire-exposed structure; and (c) material properties for determining the related mechanical behaviour and load-bearing capacity.With a summary presentation of the development and characteristics of the analytical structural fire design as a background, the paper is focusing on the mechanical material properties at elevated temperatures. A systematic scheme of classification of available tests is referred to and the importance is stressed of using such functionally well-defined tests which give material properties, stringently connected to material behaviour models being independent of the type of load-bearing structure.     

A human-scaled GIS: measuring and visualizing social interaction in Barcelona’s Superilles

Social interaction is a key component of urban sustainability, but its spatial measurement is difficult using existing off-site GIS data. This paper reports on a new method of measuring social interaction using a combination of mobile technology and parametric software, which was tested on two of Barcelona’s new semi-pedestrian superilles. The research is introduced within a theoretical framework for social interaction and cohesion adapted from a broader index of sustainability. It shows how on-site data collection can be used to measure the capacity of urban spaces to support social interaction. It is argued that the combination of mobile technologies, GIS data, and predetermined indicators of the capacity of spaces to support positive human experiences offers an important complement to more traditional methods of recording and measuring the qualities of urban spaces.