A comparison between the life cycle cost of gravel and of bituminous surfacing options for feeder roads in Ghana

Feeder roads, which constitute a key component of rural transport infrastructure, play a vital role in rural development, but only 5% of the total feeder road network in Ghana has bituminous seal surfacing. The remaining 95% have either gravel or earth surfacing. However, gravel surfacing (G-S) is known to deteriorate rather rapidly necessitating expensive frequent maintenance while bituminous surfacing offers a more durable surfacing. Various life cycle cost studies have suggested that even though G-S may have lower initial construction costs, they tend to have higher life cycle costs than bituminous seal surfaced ones. However, since most of these studies are based on ideal maintenance practices, their conclusions do not reflect actual field conditions. This study seeks therefore to compare the life cycle cost of G-S with that of bituminous seal surfacing options for engineered feeder roads in Ghana using actual cost data. Data were collected from eight feeder road projects with G-S and a similar number with bituminous surfacing from six regions of Ghana completed between 2010 and 2013. The life cycle cost for each road was computed using a discount rate of 12% and an inflation rate of 15% over an analysis period of 21 years. The results for G-S are then compared with those for single bituminous seal surfacing and for double bituminous seal surfacing. The results are further compared with those from trial sections of an experimental study of Otta seal surfacing using natural gravel and using crushed rock as aggregates. The results suggest that based on the high initial construction costs of bituminous seal surfacing and actual low maintenance intervention practices, G-S remain the least cost option. The study recommends the need for alternative surfacing technology that does not involve bitumen.     

烟煤粉爆炸性及防爆方法研究

介绍了我国11种烟煤和无烟煤的爆炸性的测试结果，分析了烟煤爆炸性特点，研究了压力、温度、氧浓度等初始条件时烟煤爆炸性的影响，提出了不同场合下烟煤的防爆方法．论述了爆炸性对防爆方法的影响。     

Thermal field of an oil bed in a nonstationary pressure field

We carried out a numerical investigation of the temperature field arising in an oil bed due to the Joule-Thomson effect and the heat of deaeration of the liquid in the nonstationary pressure field in displacement of oil by water. The formation of the temperature field depends substantially on the initial flooding of the bed and the approach of the front of the displacement of oil by water. The value of the water-oil ratio exerts an effect on the sign of the temperature anomaly at the outlet from the bed.     

水平井压裂裂缝监测与分析

水平井可以在不太厚的油层中增大钻井过油层范围,实现高速注、采,提高产量 。有些水平井需要压裂,因此常常需要了解并控制人工裂缝形态、方位。通过微地震人工裂缝监测,研究已有的水平井压裂结果,特别是钻井水平段大体沿最大水平主应力方向的水平井压裂,了解压裂裂缝形成的机制及控制方式。通过比较,进一步提高水平井钻井水平及控缝理论。     

Viscoelastic linearity limits for bituminous materials

As bituminous materials are viscoelastic in nature, their performance must be characterised using test methods and analytical techniques that account for time (or rate) of loading and temperature. In addition, it is usually advisable to confine the characterisation of a bitumen to its linear viscoelastic response (small strains) to simplify the mathematical modelling of the material, as non-linear response, particularly for viscoelastic materials, is extremely difficult to characterise in the laboratory and model in practical engineering problems. This paper describes an investigation of the linearity limits of a range of unmodified and modified bituminous binders and mixtures using a dynamic shear rheometer and a purpose-built dynamic, direct tension-compression, servo-hydraulic testing apparatus. The results show that there are strain dependent linearity criteria for both binders and asphalt mixtures at high stiffness values (low temperatures for binders and low to intermediate temperatures for mixtures) as well as a high temperature strain dependent linearity criterion for elastomeric modified binders. The linearity strain criterion for the mixtures was found to be in the order of 100 microstrain with the criterion for the binders being at least 100 times greater at just over 10,000 microstrain and the polymer network strain criterion at 1,000,000 microstrain.     

The influence of the type of loading and temperature on the modulus of elasticity of cement-bound mixes of milled bituminous concrete and crushed aggregates

Combinations in various proportions of milled bituminous concrete and crushed limestone aggregates were mixed in the laboratory with 5% by mass cement and 5% by mass water to simulate some of the materials that can be obtained when mix-in-place recycling with cement is used. The influence of the temperature and of the type of loading (different rates of stress application of ramp loading and different frequencies of sinusoidal loading) on the modulus of elasticity is examined. It is concluded that as the milled bituminous concrete content in the mix is increased, both the temperature and the rate of stress application increasingly influence the results, and this should be taken into consideration when specifying or designing pavements incorporating cement-bound materials of this type.     

Effect of oxide scale on corrosion behavior of HP-13Cr stainless steel during well completion process

The well completion process in oil and gas industry,aiming to build effective exploitation,is divided into acidizing and formation water production process.Oxide scale(OS)formed on the inner wall of the HP-13Cr stainless steel tubes during the hot extrusion process changes the surface roughness.The effects of OS on the corrosion of HP-13Cr stainless steel during well completion process were studied by corrosion measurement,spectra analysis,microscopic observation and numerical simulation.The results indicate that the OS make no change of phase distribution and element composition of corrosion scale,while the increasing OS roughness is the dominant factor for accelerating corrosion rate during the well completion process.In acidizing process,the greater surface roughness OS of HP-13Cr stainless steel increases the corrosion rate obviously due to a larger interfacial area in contact with the aggressive environment.During subsequent formation water production process,the turbulence eddy,formed at locations characterized with greater surface roughness OS,can deteriorate the corrosion scale and accelerate the mass transfer of the corrosive species,resulting in more serious corrosion.     

含废机油混装乳化炸药可行性研究

为研究废机油用于制备混装乳化炸药的可行性,采用正交实验的方法制备乳化基质,利用偏光显微镜和扫描电镜记录新制、自然储存和高、低温循环乳化基质的微观形态,并分析了废机油对乳化炸药成乳性、储存性能和爆炸能力的影响。结果表明:废机油和乳化剂在油相中的含量会影响乳化基质的成乳性,废机油与成乳性指数的相关性指数为-0.697,废机油和乳化剂的比值与成乳性指数的相关性指数为-0.674。说明废机油比例越高,废机油与乳化剂的比值越高,越难形成乳化基质。成乳后含废机油乳化基质的储存性与废机油在油相中的含量没有明显的直接关系,含废机油混装乳化炸药爆速与不含废机油混装乳化炸药接近,含废机油乳化炸药可以满足工程爆破对乳化炸药的性能要求。     

B2O3-SiO2-Na2O缓释材料的合成工艺参数优化及其缓释机理

为优化工艺参数、减少原料损失和控制生产成本, 本研究采用单因素法研究不同升温速率、保温时间、熔制温度和起始温度对硼酸盐缓释材料(BCRM)在制备过程中B₂O₃挥发量和气泡生成情况的影响规律。运用X射线衍射分析、红外光谱和X射线光电子能谱仪表征缓释前后BCRM理化性质变化, 通过Korsmeyer-Peppas模型分析BCRM缓释机理。结果表明, 在起始温度1050 ℃、保温时间2 h和熔制温度1050 ℃的最优工艺参数下, B₂O₃挥发量可降低至1.08%, BCRM澄清透明, 无气泡生成, 缓释性能良好。此外, 温度会影响BCRM的缓释机理, 在30和35 ℃时, 释放机理为Super Case II转运; 在40 ℃时, 释放机制为non-Fickian扩散。但在不同温度下, 硼累积释放率均高于95%。     

含废机油混装乳化炸药可行性研究

为研究废机油用于制备混装乳化炸药的可行性,采用正交实验的方法制备乳化基质,利用偏光显微镜和扫描电镜记录新制、自然储存和高、低温循环乳化基质的微观形态,并分析了废机油对乳化炸药成乳性、储存性能和爆炸能力的影响。结果表明:废机油和乳化剂在油相中的含量会影响乳化基质的成乳性,废机油与成乳性指数的相关性指数为-0.697,废机油和乳化剂的比值与成乳性指数的相关性指数为-0.674。说明废机油比例越高,废机油与乳化剂的比值越高,越难形成乳化基质。成乳后含废机油乳化基质的储存性与废机油在油相中的含量没有明显的直接关系,含废机油混装乳化炸药爆速与不含废机油混装乳化炸药接近,含废机油乳化炸药可以满足工程爆破对乳化炸药的性能要求。     

Growth mechanism of CdS nanofilms prepared by chemical bath deposition

Deposition of CdS nanofilms was performed using the chemical bath deposition method, as a function of the concentration ratio of [S] to [Cd] (S/Cd) and of deposition temperature. As the S/Cd ratio and deposition temperature increased, the deposition rate of the films increased, and the transmittance was improved. With increasing S/Cd ratio, the crystallinity of the CdS nanofilms decreased due to the formation of small grains therein. Atomic force microscopy revealed that the surface morphology of the films became smooth with increasing S/Cd ratio and deposition temperature. The evolution of the grain formation showed that the slow deposition rate of the films leads to a small number of grains at the initial stage of the deposition, followed by fast grain growth, resulting in a rough surface. On the other hand, a fast deposition rate initially causes the formation of many grains on the entire surface as well as slow grain growth, making the films smooth. It is evident that the deposition rate affects the physical and optical properties of the films due to their different growth mechanisms.     

Kinetics of austenite formation during continuous heating in a low carbon steel

The kinetics and microstructural evolution of austenite formation in a low carbon steel, with initial microstructure composed of ferrite and pearlite, were studied during continuous heating, by using dilatometric analysis and measurements of microstructural parameters. The formation of austenite was observed to occur in two stages: (a) pearlite dissolution and (b) ferrite to austenite transformation. The critical temperatures of austenite formation in continuous heating increase with increasing heating rate, with greater influence on the finishing temperature of austenite formation. For both the 1 °C/s and 0.1 °C/s heating rates, the formation rate of austenite reaches a maximum at approximately the finishing temperature of pearlite dissolution, and the formation rate of austenite as a function of the temperature is greater at the higher heating rate.     

载水油气井生产测井方法研究

油井或气井出现载水现象后,不断上升的水柱不仅会降低储层与井筒间的压差影响油气产出,而且改变了井筒中流体介质分布和速度分布,造成生产动态监测方面的困难。提出了依据流量计、密度计、持水率计等曲线判断油井或气井是否载水的新方法,基于对不同井段的流型进行了分析,提出了相应产出剖面测井仪器系列及其测井资料处理解释模型。     

Accelerated pavement testing and modeling of reflective cracking in pavements

In the field of reflective cracking initiation and propagation in pavement structures, an Accelerated Pavement Testing (APT) has been developed. The numerical method is also supported. Numerical results obtained by calculations made with the finite element CESAR-LCPC software are then compared with the experimental data. The reflective cracking APT experience is the first step in the development of a new laboratory equipment to evaluate the design of bituminous layers to repair pavements. The experiment was performed on a 30 m track where eight discontinuities were established by cutting-off the sub-bases in order to ensure a crack development in the bituminous layer. The conditions that promote crack propagation were reproduced by the application of heavy periodic loads using the Fabac ALT-APT test rig. The width of the bituminous layer was decreased to facilitate the observation of the crack propagation, while avoiding creep of the material. The structure has a large number of sensors that measure longitudinal and transverse deformations at the bottom and at the surface of the bituminous layer. The deflections and the displacements are measured at several levels of the structure, as well as the temperature and the lateral edge cracking which is monitored by cracking sensors on both sides of the track. Preliminary results on two joints were used to determine the mechanisms of rupture of the structure. Four more tests with improved sensors have completed the information. Experimental and numerical results are compared in order to validate the analysis of the fatigue process (debonding, damage and cracking) in full scale pavement.     

Time dependent viscoelastic rheological response of pure,modified and synthetic bituminous binders

Bitumen is a viscoelastic material that exhibits both elastic and viscous components of response and displays both a temperature and time dependent relationship between applied stresses and resultant strains. In addition, as bitumen is responsible for the viscoelastic behaviour of all bituminous materials, it plays a dominant role in defining many of the aspects of asphalt road performance, such as strength and stiffness, permanent deformation and cracking. Although conventional bituminous materials perform satisfactorily in most highway pavement applications, there are situations that require the modification of the binder to enhance the properties of existing asphalt material. The best known form of modification is by means of polymer modification, traditionally used to improve the temperature and time susceptibility of bitumen. Tyre rubber modification is another form using recycled crumb tyre rubber to alter the properties of conventional bitumen. In addition, alternative binders (synthetic polymeric binders as well as renewable, environmental-friendly bio-binders) have entered the bitumen market over the last few years due to concerns over the continued availability of bitumen from current crudes and refinery processes. This paper provides a detailed rheological assessment, under both temperature and time regimes, of a range of conventional, modified and alternative binders in terms of the materials dynamic (oscillatory) viscoelastic response. The rheological results show the improved viscoelastic properties of polymer- and rubber-modified binders in terms of increased complex shear modulus and elastic response, particularly at high temperatures and low frequencies. The synthetic binders were found to demonstrate complex rheological behaviour relative to that seen for conventional bituminous binders.     

The influence of molybdenum concentration on the magnetic permeability and kinetics of order formation in molybdenum permalloys

The initial magnetic permeabilities of molybdenum permalloys with a range of molybdenum concentrations have been measured as a function of isothermal annealing time in the temperature range 400 to 600° C. Annealing in the range from 400 to 460° C produces short-range ordering, leading to a maximum initial permeability when the magnetostriction is reduced to zero. From 460 to approximately 490 to 500° C it is suggested that microdomains of long-range order nucleate and grow in a short-range ordered matrix and these reduce the maximum initial permeability which can be obtained. Above about 490 to 500° C, long-range order does not form, but equilibrium values of short-range order are too small to produce initial magnetic permeabilities as large as in the lower temperature region. The rate of short-range order formation has been found to increase sharply at molybdenum concentrations of about 4 wt % (2.5 at. %) and the activation energy for short-range order formation falls sharply from about 180 kJ mol^–1 to 140 kJ mol^–1 at this molybdenum concentration. It is thought that different ordered structures and mechanisms of ordering occur below and above 4 wt% molybdenum. Quenching experiments suggest that quenched-in vacancies can increase the rates of short-range order production.     

The constant stress behaviour of polystyrene-low density polyethylene blends

The constant-stress behaviour of low-density polyethylene toughened polystyrene has been analysed. It was found that the initial strain-time behaviour during constant-stress tensile tests is well described by a simple model that predicts a proportionality between strain and the square of time, provided a correction for craze formation during the application of stress is made. By analysing strain-time curves at different stresses it has been determined that the product of the rates of craze initiation and of craze growth is exponentially dependent on stress. The attainment of a constant strain rate during constant-stress experiments and the attainment of a constant-stress level during constant strain-rate experiments result from a strong decrease in the rate of craze initiation. This effect allowed the determination of the stress and temperature dependences of the rate of craze growth. This rate was found to be well described by the Eyring equation, which is in agreement with earlier results obtained from constant stress- and strain-rate experiments.     

Newtonian fluid flow from an arbitrarily-oriented fracture into a single sink

Summary A model of fluid flow from an arbitrarily-oriented compressible fracture into a sink has been developed. Effects of fracture inclination, fracture dimensions, in-plane aspect ratio, fracture compressibility, sink location, sink pressure, initial equilibrium pressure inside the fracture and fracture wall roughness on fluid flow into the sink have been investigated. It has been found that the effect of fracture inclination decreases with decreasing fracture compressibility. Sink location (in the middle of the fracture, at the edge, or in the corner) has a significant effect on the fluid flow into the sink. Fluid flow into the sink is shown to be controlled mainly by the difference between the initial fluid pressure in the fracture and the sink pressure, but not by the absolute values of these parameters. The effect of the fracture wall roughness was investigated using fractures with artificial surfaces having Hurst exponent of 0.5. In case of a widely-opened fracture, the effect of roughness is negligible, and the fracture can be approximated with a smooth-walled fracture of the same mean aperture. In case of a partially-closed rough-walled fracture, the roughness was found to affect the flow rate significantly by extending the discharge time. This has an important implication for oil production from certain types of naturally-fractured reservoirs. The roughness of partially-closed fractures did not, however, affect the results of the comparative parametric study, which justified the use of a simplified smooth-wall model in such studies. Modeling results have implications for the simulation and analysis of some drilling situations in fractured rocks as well as for well testing analysis and oil production simulation.     

Numerical simulation of the five-point bending test designed to study bituminous wearing courses on orthotropic steel bridge

The structural role of the wearing courses on orthotropic steel deck bridges is usually not estimated during the design process. Both geometry of the structure and very high flexibility of steel plates induce severe stress and strain fields in the steel bridge surfacing. In this paper, we quantify the influence of a bituminous mix surfacing on the steel plate response when considering the French Five-Point Bending Fatigue Test. Mechanical behavior of bituminous mixes is very complex. It includes a great thermal sensitivity. Moreover in the small strain domain (for strain amplitudes below about 10^?4) the behavior can be considered as linear. Therefore, the theory of linear viscoelasticity can be applied. After introducing the French five-point bending fatigue test used at the research center of “EIFFAGE Travaux Publics” company, in parallel to the construction of the Millau Viaduct (France) -the highest bridge in the world-, a numerical parametric study using the Finite Element Method (FEM) is presented. The specimens are made of a 12-mm-thick steel plate, a 3-mm-thick sealing sheet and a 60-mm-thick bituminous mix. Different wearing course behaviors are considered introducing temperature and viscous effects. This behavior is modeled using the linear part of the general thermo-viscoplastic model «DBN» (Di Benedetto and Neifar), recently developed at ENTPE laboratory and briefly described in this paper. An important observation is that the rigidity of the intermediate bituminous sealing sheet as well as the wearing course behavior seems to have a great influence on the orthotropic multilayer specimen complex behavior.     

Evolution of bituminous mix behaviour submitted to UV rays in laboratory compared to field exposure

Laboratory methods to simulate the short and long term ageing occurring during the service life of pure and polymer modified bitumens in a pavement are standardized but none of them takes into account the influence of ultraviolet (UV) radiations. Recently, attentions have been paid to the laboratory ageing tests with UV radiation applied to the bituminous binders. Even if this effect of UV radiation on binder’s films have been largely demonstrated and studied, however there are few studies dealing with the photo-oxidation of binders in a bituminous mix in relation with voids, film thickness and permeability. So, the aim of our study was to investigate whether the influence of UV light on bitumen ageing might be assessed in the bituminous mixes using an experimental apparatus dedicated to the ageing of paint. The results show that the influence of UV radiation on the ageing of bituminous mixes containing an elastomer modified bitumen can not be totally ignored: compared with thermal aging, the UV impact can be distinguished and found to be dominant for the production of carbonyl functions, the disappearance of C=C double bond of SBS and the increase of binder’s hardening. So, this study has highlighted, on the one hand, that inside the bituminous mix, the UV radiations do increase the rate of oxidation and, on the other hand, that the evolution’s kinetics due to a pure thermal oxidation or a photo-oxidation processes are different: the evolution due to 44 months of on site ageing is better assessed by photo-oxidation process than by pure thermal oxidation. Consequently, the UV exposure may affect the bitumen’s properties of pavement upper layers more strongly than the PAV simulation in laboratory (without UV action) does.