Study of changes in concentration during penetration through the soil layers by means of co-relationship

This report presents a co-relationship method that is used to evaluate changes in water quality. The co-relationship based on the water quality in the Goto river basin, is defined as plots of concentration of dissolved matter against total residue on evaporation, the correlation coefficient and the regression equation. SiO₂ and COD concentrations in the water samples of the Goto river basin show a peculiar change that is independent of the total residue on evaporation and flow length, and this change is again found by means of the co-relationship. The peculiar change of SiO₂ is also observed in some rivers in Japan. The correlation coefficient of the total residue on evaporation and SiO₂ is about 0.2–0.6 in the Goto river basin and in some other rivers in Japan, and the intercept of the regression equation of SiO₂ and Cl⁻ is apt to show a plus value in SiO₂ but a minus value in Cl⁻ in most of the co-relationships. The plus value of the intercept and the gentle slope of SiO₂ show that SiO₂ concentration is independent from that of the total residue on evaporation, and the minus value of Cl⁻, shows that a certain value of total residue on evaporation corresponds to zero concentration of Cl⁻, which means Cl⁻ does not dissolve out from the soil colloid. Thus, the present report suggests that there is a peculiar behavior in some species in the water flow by means of the co-relationship.     

Diaphragm wall-soil-cap interaction in rectangular-closeddiaphragm-wall bridge foundations

Rectangular-closed-diaphragm-wall foundation is a new type of bridge foundation. Diaphragm wallsoil-cap interaction was studied using a model test. It was observed that the distribution of soil resistance under the cap is not homogeneous. The soil resistance in the corner under the cap is larger than that in the border; and that in the center is the smallest. The distribution of soil resistance under the cap will be more uniform, if the sectional area of soil core is enlarged within a certain range. Due to the existence of cap, there is a “weakening effect” in inner shaft resistance of the upper wall segments, and there is “enhancement effect” in the lower wall segments and in toe resistance. The load shearing percentage of soil resistance under the cap is 10%–20%. It is unreasonable to ignore the effects of the cap and the soil resistance under the cap in bearing capacity calculations. __________ Translated from China Civil Engineering Journal, 2007, 40(8): 67–73 [译自: 土木工程学报]     

Optimal sizing of building integrated hybrid PV/diesel generator system for zero load rejection for Malaysia

In this research, an optimisation for building integrated hybrid PV/diesel generator system for zero load rejection for Malaysia is performed. The optimisation is performed considering a loss-of-load probability (LLP) less than 0.01. However, the daily averages of solar energy for Malaysia and a mathematical model of a hybrid PV/diesel generator system are used in this optimisation. The optimisation presented in this paper aims to calculate the optimum capacities of a PV array and diesel generator, which investigate the minimum system cost. An optimisation problem in terms of system units’ cost is solved graphically in this study. Moreover, the optimised system is compared to other energy source choices to highlight its feasibility. The recommended configuration of a PV/diesel system located in Malaysia is C_A = 1.2, C_DG = 0.3, while the optimum C_B is 0.1. The results of the optimisation show that a PV/diesel generator choice is more feasible compared to a standalone PV system or diesel generator system because it reduces the system cost by 35%.     

Modified Kuz—Ram fragmentation model and its use at the Sungun Copper Mine

Rock fragmentation, which is the fragment size distribution of blasted rock, is one of the most important indices for estimating the effectiveness of blast work. In this paper a new form of the Kuz—Ram model is proposed in which a prefactor of 0.073 is included in the formula for prediction of X_50. This new equation has a correlation coefficient that is greater than 0.98. In addition, a new approach is proposed to calculate the Uniformity Index, n. A Blastability Index (BI) is used to correct the calculation of the Uniformity Index of Cunningham, where BI reflects the uniformity of the distribution. Interestingly, this correction also can be observed in the Kuznetsov—Cunningham—Ouchterlony (KCO) model, which uses In situ block size as a parameter for calculating the curve-undulation in the Swebrec function. However, it is in contrast to prediction of X₅₀ as the central parameter in Swebrec and Rosin–Rammler distribution functions. The new model is a two parameter fragmentation size distribution that can be easily determined in the field. However, it does not consider the timing effect, or upper limit for sizes, as does the original Kuz—Ram model. The model is used at the Sungun Mine, and it does a good job of predicting the fines produced during blasting.     

A nonlinear strength criterion for rock-like materials based on fracture mechanics

A nonlinear strength criterion for rock-like materials is developed in this paper. Taking α as an angle of micro-failure orientation in rock-like materials, a formulation between α and load is derived from a mixed-mode fracture criterion based on linear elastic fracture mechanics. According to micro-failure experimental phenomena of rock-like materials, a failure characteristic parameter under triaxial compression condition is chosen, which is relevant to confining pressure and is an invariant. A theoretical nonlinear strength criterion is also derived, which is exactly in the same mathematical form as the original Hoek–Brown empirical strength criterion. In addition, it is also found that the coefficient m in the Hoek–Brown criterion has physical meaning which is related to the ratio between the uniaxial compressive strength and the uniaxial tensile strength.     

An experimental study on backdraught: The dependence on temperature

This paper presents the results of a series of reduced scale experiments to investigate the temperature conditions leading to backdraught in a fire compartment (0.8 m×0.4 m×0.4 m), using solid polypropylene pellets as the fuel. The factors of primary interest are the pre-burn time, before the fire becomes oxygen limited, the duration of door closure, and the temperature distribution in the compartment. It is shown that the temperature inside the compartment is crucial for the occurrence of backdraught. Above 350 °C, backdraught by auto-ignition is possible. If a pilot spark is present, backdraught may occur at temperatures down to 300 °C. It is shown that backdraught conditions can be achieved in the early stages of a fire as long as a suitable temperature is reached, at considerably lower temperatures than those generated during flashover. Further investigation on gas concentration is essential to understand the chemistry of backdraught combustion.     

Caffeine as an indicator for the quantification of untreated wastewater in karst systems

Contamination from untreated wastewater leakage and related bacterial contamination poses a threat to drinking water quality. However, a quantification of the magnitude of leakage is difficult. The objective of this work is to provide a highly sensitive methodology for the estimation of the mass of untreated wastewater entering karst aquifers with rapid recharge. For this purpose a balance approach is adapted. It is based on the mass flow of caffeine in spring water, the load of caffeine in untreated wastewater and the daily water consumption per person in a spring catchment area. Caffeine is a source-specific indicator for wastewater, consumed and discharged in quantities allowing detection in a karst spring. The methodology was applied to estimate the amount of leaking and infiltrating wastewater to a well investigated karst aquifer on a daily basis. The calculated mean volume of untreated wastewater entering the aquifer was found to be 2.2 ± 0.5 m³ d⁻¹ (undiluted wastewater). It corresponds to approximately 0.4% of the total amount of wastewater within the spring catchment.     

Effect of probabilistic variation in soil properties and profile of site response

Site response is a function of the soil profile, and the probable distribution of the soil profile has a significant effect on the seismic site response. In the present study, the influence of random variations in soil characterizations on the site response is investigated using different probabilistic distributions. The important characteristics of the local soil, corresponding to the layering, the shear wave velocity ($V_s$), the decrease in the nonlinear modulus, and the damping (MRD) curves, are considered when carrying out these random variations. Stochastic processes are generated by using different distribution models and keeping in mind the effect of the coefficients of the variations. In this research, a proposed procedure is developed and coded to perform the variations in soil characterizations. The coding of this new procedure is based on the original SHAKE91 framework. However, instead of using the fixed soil properties and profile, the uncertainties of the MRD curves, the layer thickness, and $V_s$ are generated as the input data. This analysis shows that the use of median $V_s$, obtained from all the possible inputs under the different stochastic processes, yields good agreements with the baseline profile. Modelling the variabilities in the layering and the $V_s$ profile is seen to have a slight effect on the performance of the site response. Additionally, the results of these analyses indicate that the variabilities in nonlinear soil properties have a significant impact on the median surface response spectrum and the amplification spectrum of the surface motions.     

Nitrate behaviour in streamflow from a grassland catchment in Devon, U.K.

NO₃---N levels and loadings in the River Dart, Devon, U.K. have been intensively monitored during the study period February 1975–January 1983, and NO₃---N behaviour in streamflow is compared with that of Mg which has predominantly contrasting origins and controls in runoff. A strongly developed annual regime characterises daily mean NO₃---N concentrations which peak at 4.5 mg l⁻¹ in December and reach a minimum of 1.1 mg l⁻¹ in early autumn, and this regime is reflected in a positive relationship between NO₃---N concentration and discharge. Storm-period NO₃---N behaviour also exhibits a marked seasonal variation, and “dilution” responses are typical of the winter period whereas a “concentration” effect is more characteristic of summer months and is attributed to the influence of soil throughflow. Spring and autumn are associated with a transition in storm-period behaviour, and the reaction of NO₃---N concentrations during individual events or over a sequence of storms at any time of the year may also vary in response to a complex interplay of factors.NO₃---N transport is more strongly biased towards storm events than is Mg, and more than 50% of the total NO₃---N load was removed in only 10% of the study period. The mean annual NO₃---N load for the study basin (24 kg ha⁻¹) is higher than that recorded in many grassland catchments of the U.K. but does not reflect an unusually high rate of fertiliser application. Unlike several other arable and grassland drainage basins studied in Britain, there is no evidence in the River Dart of a significant upward trend in NO₃---N concentrations and loads since 1975.     

Biosphere reserves and the “Yucatán” syndrome: another look at the role of NGOs

After centuries of cultural and economic conquest of the Americas by European and Euro-American conquistadors, contemporary rhetoric in ex-colonial powers heralds the decline of material and ideological imperialism. Instead, it is purported that today's world is peopled by a great brotherhood, with the more affluent striving to relieve their less fortunate, underdeveloped kith. This conviction is inherent in organizations which dispense money, information, training, and other resources in the name of community development and endangered species and environmental conservation. What is rarely perceived – and practically never said – is that these “benevolent” foreign aid activities typically result in the concentration of resources and power in the hands of a few, the building of empires, and the compounding of already difficult situations, counter-productive to stated objectives. The Yucatán Peninsula is a classic case of persistent imperialism: the geographic name is a corruption of the Mayan “matan cub a than” (“I do not understand you”), while contemporary development and conservation programs habitually exhibit cultural ignorance and dominance. This paper explores a diverse literature on non-governmental organizations, reflects on likely consequences of cultural dominance, and implores professional anthropologists to be adventurous in propagating anthropological knowledge relevant to environmental protection.     

Ventilation effectiveness measures based on heat removal: Part 1. Definitions

The effectiveness of ventilation flows is considered from the perspective of buoyancy (or heat) removal from a space. This perspective is distinct from the standard in which the effectiveness is based on the concentrations of a neutrally buoyant contaminant/passive tracer. Three new measures of effectiveness are proposed based on the ability of a flow to flush buoyancy from a ventilated space. These measures provide estimates of instantaneous and time-averaged effectiveness for the entire space, and local effectiveness at any height of interest. From a generalisation of the latter, a vertical profile of effectiveness is defined. These measures enable quantitative comparisons to be made between different flows and they are applicable when there is a difference in density (as is typical due to temperature differences) between the interior environment and the replacement air. Applications, therefore, include natural ventilation, hybrid ventilation and a range of forced ventilation flows. Finally, we demonstrate how the ventilation effectiveness of a room may be assessed from simple traces of temperature versus time.     

Compressibility of biocemented loose sands under constant rate of strain,loading, and pseudo K0-triaxial conditions

The compressibility behavior of loose sands treated with Microbially Induced Carbonate Precipitation (MICP) is presented in this paper. The paper discusses the strain rate effects and evolution of at-rest earth pressure coefficient and elastic shear modulus during $K_0$-loading. The soil samples were prepared in a triaxial cell in which a biological solution containing the ureolytic bacteria Sporosarcina pasteurii was injected and held under a small back pressure. Cementation treatments were injected following an alternated top and bottom sequence. The constant rate of strain, constant rate of loading, and pseudo $K_0$-triaxial tests were performed at different strain and stress rates. On-specimen internal instrumentation consisting of a submersible load cell, three Hall Effect transducers, and vertical Bender Elements were used to control radial strains during $K_0$-loading and measure small-strain shear modulus changes. Based on shear wave velocity measurements, the MICP-treated sand was lightly cemented and displayed soil-like behavior. The experimental results demonstrated a significant reduction in soil compressibility after MICP treatment. The material response was remarkably similar for every tested strain rate. The very small values of axial strains measured for the biotreated samples in relation to untreated control specimens for vertical effective stress levels below 200 kPa is evidence of the suitability of this treatment and shows its potential for use in field applications at relatively shallow depths.     

Simplified elasto-plastic analysis of composite beams and cellular beams to Eurocode 4

The elasto-plastic analysis of composite beams is important when considering the increase in bending resistance of the beam and the end slip between the steel and concrete at higher strains. This paper provides a simplified method of elasto-plastic analysis by considering equilibrium of the composite cross-section as a function of its strain profile. A parabolic-rectangular stress block for concrete is used in this model with a declining concrete strength at strains exceeding 0.0035. The bending resistance of the composite beam is expressed as a function of the bottom flange strain, and is compared to fully plastic design to EN 1994-1-1: Eurocode 4 and the AISC LRFD Code.The effect of various parameters on the development of the plastic bending resistance of composite beams is investigated, such as asymmetry of the section, the steel strength, the influence of propped or un-propped construction, strain hardening in the steel and reducing concrete strength at high strains, interface slip, and the effect of openings in the web of the beams. It was found that a moment of 95% of the plastic bending resistance of a composite beam (0.95M_p?) is reached at a flange strain of 2 to 4 × yield strain for propped beams and 5 to 10 × yield strain for un-propped beams. When strain hardening in the steel is included in the analysis, bottom flange strains at a moment of 0.95M_p? are reduced by up to 30% relative to the case without strain hardening.     

Exergy concept and its application to the built environment

This paper discusses how a built environmental control system such as space heating and cooling can be described by the concept of “exergy”, which quantifies what is consumed by any working systems from man-made systems such as heat engines or buildings to biological systems including human body. The reason for the intensive and extensive use of exergy concept is to deepen our understanding of the built environment and thereby to develop a variety of low-exergy systems for future buildings. First, the essence of exergy balance equations is reviewed and then some results obtained from the recent exergy research were presented. The important findings described in this paper are as follows: (1) a volume of indoor air contains both of “warm” or “cool” exergy and of “wet” or “dry” exergy, whose values are comparable to each other especially for a hot and humid summer condition; (2) an ordinary air-source heat pump is basically a device to separate exergy supplied by electricity into warm, cool and dry exergies by consuming more than 85% of the supplied exergy; (3) there is a set of a little higher mean radiant temperature and a little lower air temperature, which provides with the lowest human body exergy consumption rate in winter season; (4) availability of cool radiant exergy of 20–40 mW/m² seems to play a key role for thermal comfort in a naturally-ventilated room in summer season; and (5) “cool” radiant exergy available from the sky in hot and humid regions amounts to 1000 mW/m², which is not necessarily small if compared to the values of cool radiant exergy to be supplied indoors.     

Application of Micromechanics Model to Study Anisotropy of Soils at Small Strains

A micromechanics model is used to analyse the stiffness anisotropy of soils at small strains. Five material constants for a cross-anisotropic elastic material are related to micromechanics variables such as fabric anisotropy, contact stiffness, particle radius, and the number of contacts in a given volume of particulate assembly. The analytical results from the model are compared with the published experimental data on small-strain stiffness anisotropy in order to estimate typical soil fabric conditions of sands and clays. The relationship between the small-strain shear modulus obtained from triaxial tests and shear tests is examined using the micromechanics model. The analysis shows that, when a soil is stiffer in the horizontal direction, the shear modulus evaluated from the conventional triaxial drained tests underestimates G_vh and G_hh. The opposite is true when a soil is stiffer in the vertical direction. When a soil is sheared in undrained condition, the measured shear modulus is closer to G_vh than G_hh, especially when the soil is stiffer in the horizontal direction. The effect of soil anisotropy on the stiffness measured from different stress paths in triaxial condition is investigated.     

Building simulation as an assisting tool in decision making: Case study: With or without a double-skin façade?

Implementation of double-skin façades in buildings has been an object of broad application in the recent years. In this presentation, a planned office building in the city-centre of Trondheim, Norway, is used as a case for considering whether a double-skin should be applied to the east façade in order to reduce the heating demand, thus making the double-skin façade a profitable investment. The building is modeled both with and without a double-skin façade with the building energy simulation program ESP-r. This paper describes how a double-skin façade with controllable windows and hatches for natural ventilation can be implemented in the simulation program. The simulation results indicate that the energy demand for heating is about 20% higher for the single-skin façade with the basic window solution compared to the double-skin alternative. However, by switching to windows with an improved U-value in the single-skin alternative, the difference in energy demand is almost evened out. The number of hours with excessive temperatures is, in contrast to other studies on the subject, not significantly higher for the double-skin alternative. However, the predicted energy savings are not sufficient to make the application of a double-skin façade profitable.     

Causes of weight reduction effects of material substitution on constant stiffness components

The substitution of lightweight materials, such as aluminum or magnesium alloys, to produce lightweight car bodies, has been the subject of intensive research in recent years. It has been established that an aluminum body is lighter than a steel body for constant stiffness. The causes of this weight reduction have not been established. In particular, since the specific modulus (modulus of elasticity/density) of steel, aluminum and magnesium are nearly identical, there is no easy answer for their ability to reduce weight.In this paper, it is shown that there are thin-walled effects that are dependent on the thickness of the material. These thin-walled effects appear in joints and other parts with complex geometry and loading conditions and can significantly weaken the part. For example, the flanges on a curved beam in flexure have an effective (load-bearing) width that increases as the material is thickened. A part made of thicker material uses its material more efficiently (has a higher percentage of load-bearing material) than a thinner part. This thickness dependence is important because thin-walled parts made from lightweight materials, such as aluminum, are thicker than their steel counterparts; hence the parts made from lightweight materials use their material more efficiently. It is further shown that reducing these thin-walled effects through better reinforcements produces significant weight reduction effects and also reduces the weight reduction effects of substituting aluminum for steel. Thus a strong, lightweight body can be achieved using steel and proper design of joints and other complex geometry parts. This is a more cost-effective way of achieving a lightweight body.The concept of a structural index, λ, is developed and applied to the joints of a truck cab. It is assumed that when performing material substitution, only the thickness, t, is changed. It is shown that the stiffness, K, of the beam can be defined as a function of t^λ, that 1≤λ≤3, and that λ can be used to predict the weight savings from material substitution where stiffness is held constant. It is then demonstrated that λ can be used to predict the weight savings from material substitution in the more complex cases of the joints of a light truck cab.