Review of Laboratory Scale Models of Karst Aquifers: Approaches,Similitude, and Requirements

This review focuses on investigations of groundwater flow and solute transport in karst aquifers through laboratory scale models (LSMs). In particular, LSMs have been used to generate new data under different hydraulic and contaminant transport conditions, testing of new approaches for site characterization, and providing new insights into flow and transport processes through complex karst aquifers. Due to the increasing need for LSMs to investigate a wide range of issues, associated with flow and solute migration karst aquifers this review attempts to classify, and introduce a framework for constructing a karst aquifer physical model that is more representative of field conditions. The LSMs are categorized into four groups: sand box, rock block, pipe/fracture network, and pipe-matrix coupling. These groups are compared and their advantages and disadvantages highlighted. The capabilities of such models have been extensively improved by new developments in experimental methods and measurement devices. Newer technologies such as 3D printing, computed tomography scanning, X-rays, nuclear magnetic resonance, novel geophysical techniques, and use of nanomaterials allow for greater flexibilities in conducting experiments. In order for LSMs to be representative of karst aquifers, a few requirements are introduced: (1) the ability to simulate heterogeneous distributions of karst hydraulic parameters, (2) establish Darcian and non-Darcian flow regimes and exchange between the matrix and conduits, (3) placement of adequate sampling points and intervals, and (4) achieving some degree of geometric, kinematic, and dynamic similitude to represent field conditions.     

Flood occurrence hazard forecasting based on geographical information system

The application of Geographical Information system (GIS) in modeling flood and its prediction in catchments offers considerable potential. Several examples illustrate simple GIS techniques to produce flood hazard indices or its zonation using hydrologic-type models. Existing flood models can also be loosely coupled to a GIS, such as the HMS (Hydrological Modeling System) model. Forethermore, models can be fully integrated into a GIS by embedded coupling, such as the SCS (Soil Conservation Service) model. Installation of flood forecasting systems in watersheds with incomplete hydrometric data may reduce the flood-induced damages. In this study Geographical Information system used to up to date the watershed data and estimation of SCS model parameters which is sensible to considered the real time flood forecasting in Kasilian catchment of Mazandaran province. The main aim of this paper is to investigate the possibility of the linkage between GIS with a comprehensive hydrologic model, especially HMS. The use of GIS could produce a suitable agreement between observed results (extracted rainfall and runoff data of 1992, 1995 and 1996 from the related stations) with the calculated results of the hydrological model. The obtained results from rainfall-runoff process simulations of the model in this research showed that submergibility of the main watershed, Kasillian, does not depend on the outlet discharge rate of each one of its watershed independently. But it is related to how those two outlet hydrographs from main river watershed are combined. The model is capable of showing the flood characteristics temporally and spatially in each cross section of the channel network.     

3-D dynamic foundation-soil-foundation interaction on layered soil

In this work the interaction between adjacent rigid, surface foundations resting on a viscoelastic layered soil medium is studied. A 3-D frequency domain BEM formulation in conjunction with infinite space fundamental solutions and the so called `successive stiffness method', initially developed for elastostatics and adapted here for the solution of elastodynamic problems, are used for the simulation of a layered soil medium. As a result, a discretization of the soil-foundation interface and the surrounding free surface as well as the soil layers' interfaces is necessary. However, it is shown in this work that reasonably accurate results can be obtained by using a substantially reduced discretization scheme involving only a small portion of the free surface surrounding the foundation and the corresponding interfaces of the soil layers. The presented numerical results demonstrate the importance of the dynamic foundation-soil-foundation interaction phenomenon which becomes even more pronounced where the supporting soil medium is made up of relatively shallow layers close to its free surface.     

The molecular weight distribution of coal extracts. Coalification is not a condensation polymerization

The pyridine extracts from Bruceton and Illinois No. 6 coals were fractionated using gel permeation chromatography and the molecular weight of each fraction was measured using vapor pressure osmometry. If, as has been suggested, coalification is a simple condensation polymerization from a mixture of monomers with gel formation, then as the molecular weight of the components increase, their concentration should decrease. Exactly the opposite behavior is observed. The number average molecular weights for the Bruceton and Illinois No. 6 extracts respectively are 860 daltons and 1100 daltons while the corresponding weight average molecular weights calculated from the molecular weight distribution are 2300 daltons and 2700 daltons.     

Comparing different statistical models for assessing Fe-contaminated soils based on VNIR/SWIR spectral data

Two statistical models including partial least squares regression (PLSR) and principal component regression were comparatively utilized to determine the predictive accuracy of visible–near-infrared and short-wave infrared reflectance spectroscopy in quantifying the Fe concentration in contaminated soils. Two scenarios were applied to select the best model: Scenario I included all wavelengths (400–2450 nm) and Scenario II encompassed characteristic bands of Fe. Pre-processing techniques used to select the best model included: first and second derivatives (FD and SD), multiplicative scatter correction (MSC) and standard normal variate. The abilities of the predictive models were evaluated by splitting soil samples into two random groups (80 and 20%). The first group (80%) was used to evaluate calibration and validation sets by employing the cross‐validation method, and the second group (20%) was applied to test the models. The coefficient of determination (R ²), root mean square error and residual prediction deviation were calculated to evaluate the models. Applying Scenario I indicated that the PLSR model with SD pre-processing was a more accurate technique for predicting the Fe concentration, whereas in the Scenario II, the PLSR model with MSC pre-processing had a better performance. Comparing Scenarios I and II indicated that the more reliable models for predicting the soil Fe content could be constructed by the PLSR model with the SD pre-processing techniques and all wavelengths. The modeling results produced by the PLSR model with the SD pre-processing could be used to detect, map and monitor Fe-contaminated soils by proximal and remote sensing in the mining areas.     

Performance-based assessment of an innovative braced tube system for tall buildings

In this paper, an innovative seismic lateral force resisting system for tall buildings is introduced. In this system, a novel supplemental part, ribbed bracing system (RBSyst), is attached to Braced Tube System, creating a modified BTS. RBSyst is a supplemental part which is attached to the conventional bracing members to eliminate buckling problem. The behavior of RBSyst under tensile force is similar to that of the conventional braces. However, in compression, it prevents the braces from buckling by length reduction. In order to evaluate the efficiency of this new BTS system by performance-based assessment, two typical 40-story tall buildings with different story modules equipped with this proposed bracing system are modeled numerically. Then, the seismic behavior of these 3-dimensional models are evaluated by nonlinear time history analysis under maximum considered earthquakes and service-level earthquakes. The results of the analysis demonstrate that the performance of the tall buildings equipped with this new BTS system is within the acceptable limits under both service-level and maximum considered earthquake ground motions. Additionally, it is shown that RBSyst part can effectively enhance the seismic behavior of BTS systems.