Use of a laser camera scanner to highlight the surface degradation of stone samples subjected to artificial weathering

A vision technique system was implemented in order to highlight the deterioration developing on the surfaces of stone samples during an artificial ageing test with marine spray. The system, which employs a matrix CCD camera and a laser beam, provides various kinds of information about the decay suffered by the stone samples, by comparing two types of visual information at different times throughout the ageing test: the partial digital images of the sample surfaces and then the surface relief and laser light reflection obtained by casting a sheet of laser light on to the material. The accuracy of the laser camera scanner is evaluated in the first part of this paper. The methodology was successfully used to identify the degradation morphologies occurring on five types of limestone exposed to salt spray, and to quantify the deterioration using statistical parameters computed from digitized visual data.     

湿贴人造石材整体方案研究

通过对湿贴人造石材应用中常见的问题所产生的原因进行分析，提出了人工石材应用中常见的问题和技术可靠、经济、有效的解决方案。     

Evidence of a bacterial carbonate coating on plaster samples subjected to the Calcite Bioconcept biomineralization technique

Degradation of historical buildings is mainly due to the intrusion of water which is the main vector of pollutants. Different types of surface treatment have been proposed to avoid or limit this effect. One alternative to chemical treatments is the use of the carbonatogenesis property of some bacteria. This bacterial production has been evidenced on concrete and on limestone samples in an aqueous environment. However, the carbonate production was measured indirectly and the experimental protocol was far from real conditions of use. In this paper, with the same protocol as an industrial one, and using a surface selective investigation method, grazing incidence X-ray diffraction, we show the structural and morphological evolution of the carbonate coating produced on model plaster samples. This substrate was chosen in order to unambiguously detect the bacterial carbonate production.     

三维激光扫描在测量中的应用现状

简要介绍了三维激光扫描系统的研究背景和分类,着重阐述了三维激光扫描系统在逆向工程、历史古建筑的保护、变形监测、减灾等方面的应用,指出三维激光扫描的普及应用将给测绘学科带来新的发展机遇。     

System reliability evaluation of in-service cable-stayed bridges subjected to cable degradation

Abstract

The cables in a cable-stayed bridge are critical components supporting the long-span girders and ensuring their functionality. However, cables are prone to fatigue damage and atmospheric corrosion, which directly affect the bridge safety. This study presents a framework for system reliability evaluation of in-service cable-stayed bridges subjected to cable degradation. The effect of cable strength degradation on the system reliability is demonstrated through simulation on a parallel-series system representation. Learning machines are utilised to approximate the non-linear and dynamic response functions of critical components due to cable rupture, and the system reliability is finally evaluated from the event tree established by the β-unzipping method. Both short-span and long-span cable-stayed bridges are selected as prototypes to investigate the influence of cable degradation on the system reliability. On this basis it is revealed that cable degradation can significantly influence the collapse mechanism of a cable-stayed bridge and thereby lead to a significant reduction in the system reliability. This phenomenon is associated with cable spacing, where a spare cable system seems more sensitive to cable gradation. It is demonstrated that the consideration of cable corrosion and correlation is essential for lifetime safety evaluation of in-service cable-stayed bridges.     

Fatigue properties of intact sandstone samples subjected to dynamic uniaxial cyclical loading

In this paper, the fatigue behaviour of intact sandstone samples obtained from a rockburst prone coal mine and studied under dynamic uniaxial cyclic loading in the laboratory is presented. Tests were conducted on dry and saturated samples with loading frequencies ranging from 0.1, 1 and 10 Hz and amplitudes of 0.05, 0.1 and 0.15 mm. From the laboratory investigations, it was found that the loading frequency, as well as the amplitude, was of great significance and influenced the rock behaviour in dynamic cyclic loading conditions. The dynamic fatigue strength and the dynamic axial stiffness of the rock reduced with loading frequencies and amplitude. The dynamic modulus was found to increase with the loading frequency but decrease with the amplitude. In the case of the saturated samples, it was found that the dynamic fatigue strength reduced by approximately 30 per cent, while the dynamic Young's modulus reduced by about 20 per cent. From the presented study, the dynamic energy was found to be independent of the testing conditions while other rock properties were found to be dependent on these. Finally, it was concluded that rock would more readily succumb at low frequencies and amplitude than at high frequencies and amplitude for a given energy availability.     

三维激光扫描仪在建筑物立面测量中的应用

三维激光扫描是一种先进的全自动高精度立体扫描技术,在建筑物立面测量领域,可实现对建筑物无接触性的快速扫描,同时将获得的点云信息快速转换成计算机可以处理的数据的高效测量方式.本文结合广州市对口扶贫“名村名镇建设”,提出了基于三维激光扫描技术的立面测量生产流程,并开展了一系列建筑立面测量项目,取得了较好的成效.     

Experimental relation between shear strength under low pressure and S-wave velocity of rock subjected to mechanical weathering

The reduction in the shear strength of rock exposed on slope surfaces due to mechanical weathering is a ubiquitous phenomenon in regions where extreme environmental conditions prevail, i.e., repeated changes in temperature and moisture. In dealing with the slope instability problems in such regions, the long-term effects of weathering on the strength, deformation and durability characteristics of exposed rock are envisaged in this study. Therefore, in addition to conducting multiple-cycle standard slake durability tests on rock samples taken from the lithologies of Pakistan and Japan, and on artificial soft rock, the decrease in strength and stiffness is also studied by reproducing mechanical weathering in the laboratory. The reproduced laboratory weathering (RLW) is conducted with a new device that enables vacuumed saturation, freezing, thawing, drying and cooling under a maintained level of confining pressure. The decrease in strength, stiffness and durability is elucidated from the test results, which indicate that rock having a very low level of reference strain (shear strength/modulus at small strain) is resistant to RLW and slaking. Intact rock exhibits very low reference strain and this reference strain increases with an increase in the degree of weathering, which is the case of weathered rock. The decrease in the strength of rock is an important property for judging the safety of rock slopes undergoing weathering. Thus, the relation between the strength and the S-wave velocity of rock undergoing weathering is established. The authors recommend the use of this relation for a quick assessment of the strength of rock by briefly measuring the S-wave velocity of the weathered surface layer. The relationship will assist practitioners in quickly screening potentially unstable slopes.     

Use of artificial neural networks to evaluate the effectiveness of riverbank filtration

Riverbank filtration (RBF) is a low-cost water treatment technology in which surface water contaminants are removed or degraded as the infiltrating water moves from the river/lake to the pumping wells. The removal or degradation of contaminants is a combination of physicochemical and biological processes. This paper illustrates the development and application of three types of artificial neural networks (ANNs) to estimate the effectiveness of two RBF facilities in the US. The feed-forward back-propagation network (BPN) and radial basis function network (RBFN) model prediction results produced excellent agreement with measured data at a correlation coefficient above 0.99 for filtrate water quality parameters, including temperature as well as turbidity, heterotrophic bacteria, and coliform removal. In comparison, the fuzzy inference system network (FISN) predicted only temperature and bacteria removal with reasonable accuracy. It is shown that the predictive performances of the ANNs depend on the model structure and model inputs.     

Fatigue and damage properties of non-consecutive jointed mudstone samples subjected to cyclic triaxial loading

Bulletin of Engineering Geology and the Environment - Non-consecutive jointed mudstone samples with dip angles (0° is the horizontal axis) of 15°, 30°, and 45° were subjected to...     

A sensitivity study for the visualisation of bacterial weathering of concrete and stone with computerised X-ray microtomography

Geologists and engineers recently have adopted computerised X-ray microtomography (microCT), a radiological imaging technique, for geological and petrophysical applications such as the assessment of sediment characteristics, CT-measurement of compressibility and compaction, multiphase flow studies, measurement of bulk density and moisture content, and of porosity and permeability. This study focuses on another application: the monitoring of biological weathering of natural building stones and concrete. Microbial activity as a determining factor in the deterioration process of building materials has a major economic impact. Because of its non-destructive character, microCT could be the ideal monitoring technique. With this technique, three-dimensional (3D) images of the entire inner structure of the material can be obtained, together with quantitative data. In depth changes of porosity of concrete and stone specimens due to bacterial weathering were assessed in this work. Also, porosity was visualised based on 3D data with homemade software. Scanning electron microscopy (SEM) images provided additional information and supported conclusions drawn from the X-ray microCT data. Resolution improvement will make the study of petrophysical aspects of physical weathering and/or biological deterioration processes of natural building stones and concrete a promising subject for further microCT-application.     

Computation of displacements of a swelling soil subjected to variations in the moisture/thermal conditions at its surface

Conclusion From the comparison of the theoretical and experimental graphs, it can be concluded that the proposed model describes the dynamics of the swelling process very well. This permits the magnitude of the displacements of a swelling soil to be predicted, and to establish on a well-founded basis the measures which will ensure normal operation of structure on such soils.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 24–27, September–October, 1972.     

Mechanical characterization of small shale samples subjected to fluid exposure using the inclined direct shear testing device

The mechanical strength, elastic moduli, and other properties of shale are known to be highly sensitive to any variation in pore fluid content and pore fluid chemical composition. To date, all existing rock mechanics testing procedures and studies attempting to quantitatively quantify these changes employ standard methods and techniques, i.e., shale testing under hydrostatic confinement, triaxial tests, or direct shear tests, which require very long fluid circulation time due to the intrinsic low hydraulic permeability and low solute diffusivity of shale rocks and large sample size recommended by these conventional methods. Moreover, standard-size samples for conventional rock testing methods are not always available, and the use of non-conventional size samples is sometimes required. In this work, shale testing and results on rock sample the size and shape of a stack of a few pennies are presented. The inclined direct shear test, an innovative patent-pending testing method for small and thin rock specimens, has been developed to facilitate mechanical strength characterization under variable confining pressure, with tested material exposed to different fluids at any desired exposure time, while dynamic elastic moduli can be simultaneously monitored as functions of applied stress state. This device has been compared to standard triaxial test with excellent results. Practical applications using the inclined direct shear testing device (IDSTD^TM) for three shale rocks of different natures are also presented herein.     

考虑表层损伤的混凝土硫酸盐侵蚀过程分析

服役过程中,混凝土表面会因为各种因素造成表层损伤。考虑了表层损伤造成的硫酸盐扩散系数差异,基于Fick第二定律和分子反应动力学,建立了考虑表层损伤影响的混凝土中硫酸盐侵蚀扩散反应方程及其有限差分求解模型,在此基础上开展了混凝土硫酸盐侵蚀过程数值模拟。研究结果表明,表层损伤对混凝土的硫酸盐侵蚀过程有明显影响,导致内部硫酸根离子浓度和膨胀性物质钙矾石生成量的增加,其影响随损伤程度及损伤区深度的增加而增加;混凝土表层损伤对内部硫酸根离子浓度分布的影响主要体现在侵蚀早期,而混凝土表层损伤对钙矾石生成量的影响体现在整个侵蚀过程。     

Study on the microstructure of thin-layer facade plasters of thermal insulating system during artificial weathering

Investigations involving the influence of simulate weathering on the microstructure of thin-layer plasters laid on foamed polystyrene are reported. In order to examine internal changes, two kinds of properties were examined in time per 100 cycles during 400 cycles. One of the properties is an open porosity connected with pore structure tested by the mercury intrusion method (MIP), and total porosity examined by helium intrusion technique (HIP). The other property is mineral composition analyzed on X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results have shown that changes of porosity, pore structure and chemical microstructure of plasters occured after successive weathering. In tested plasters, greater changes were noticed above the gaps of thermal insulation boards than beyond them. Porosimetry tests resulted in greater variations of open porosity over the gaps. Similarly, higher amounts of calcium carbonate were found in plasters and background mortars in places over the gaps of polystyrene boards.     

技术创新打造中国人造石精品制造商

近日在商场中发现，一种可以取代高压锅的电压力煲产品已初显“气候”。据商场专卖人员介绍，这种产品由于“出道”较晚，还没有象高压锅那样被广泛认知，但近一段时间以来，在老板等厨卫名牌的大力推动下，已开始迅速“走红”。