Excess pore pressure observation in marine sediment based on Fiber Bragg Grating pressure sensor

Abstract

Fiber Bragg Grating (FBG) technology has emerged as a relatively new sensing technology for engineering applications because of lots of advantages. In this study, a large diameter probe instrumented with FBG pressure sensors to monitor excess pore pressure in marine sediment is proposed. The principle of FBG differential pressure sensor was introduced. Laboratory tests were carried out to check the workability and stability of the FBG pressure sensor. Offshore field test was also conducted in a wharf in Qingdao of China to evaluate the feasibility of the proposed probe. The installation procedure of the probe was introduced in detail. The excess pore pressure in dissipation test, after installation and pulling process were reported. The permeability coefficient of marine sediment was calculated based on the measured data. The field data show that the proposed probe based on FBG pressure sensor has good feasibility and accuracy in monitoring the excess pore pressure of marine sediment. The generation and dissipation of excess pore pressure is closely related to the degree of soil disturbance. The variation of excess pore pressure after installation can reflect the tide well in the site.     

Experimental Investigation on Flow Characteristics at Leeside of Suspended Flexible Curtain for Sedimentation Enhancement

A new patent registered device-suspended flexible curtain (SFC) for sedimentation enhancement is proposed in this paper, which consists of two parts: a light-weight curtain with sediment-passing windows and a heavy pillar for the device stability. The mechanism of trapping nearbed sediment by the SFC is such that a primary and a secondary circulations with horizontal hubs would be formed at the leeside when it is placed on beds in running flow; the velocities within the sediment-passing windows are locally ...     

Scale effects of Hortonian overland flow and rainfall‐runoff dynamics: laboratory validation of a process‐based model

Hortonian runoff was measured in the laboratory from uniform slopes of lengths of 1·5, 3·0, and 6·0 m for steady, high‐intensity rainstorms with durations of 1·0 to 7·5 min. A clear reduction in runoff per unit slope length was found as slope lengths were increased. This effect becomes more pronounced with decreasing storm duration. The runoff data were used to validate a simple process‐based model that combines the Philip‐two‐term infiltration equation with the kinematic wave overland flow principle. The predicted and experimental results agreed well. Laboratory findings were extrapolated with the aid of the model to slopes and rainfall durations similar to those found under West African conditions. The calculated reduction of runoff per unit length is similar to reported observations. Thus, this process‐based model can largely explain the phenomenon of runoff reduction with increasing slope length. Copyright © 2002 John Wiley & Sons, Ltd.     

Structural features and mechanical behaviour of a pyroclastic weak rock

The results of an extensive programme of laboratory testing on intact and reconstituted samples of a pyroclastic weak rock from the volcanic complex of the Colli Albani (Central Italy) are presented. The deposit is known as Pozzolana Nera and may be assimilated to a bonded coarse grained material. The nature of bonds and the micro‐structural features were examined by means of diffractometry, optical and electron microscopy. As bonds are made of the same constituents of grains and aggregates of grains, bond deterioration and particles breakage upon loading are indistinguishable features of the mechanical behaviour. The testing programme consisted mainly of one‐dimensional and drained and undrained triaxial compression tests in a wide range of confining pressures up to 58 MPa. As confining stress increases, the mechanical behaviour of the material changes from brittle and dilatant to ductile and contractant; for both brittle and ductile behaviour failure is associated with the formation of shear surfaces separating the sample in several parts at the end of test. The experimental stress–dilatancy relationships are compared with the classical stress–dilatancy theories for a purely frictional material and for a material with friction and cohesion between particles. The analysis of the data indicates that peak strength results from the interplay between degradation of inter‐particle bonds, increasing friction between particles and increasing rate of dilation. Copyright © 2001 John Wiley & Son, Ltd.     

Green Laboratories: University Campuses as Sustainability “Exemplars” in the Arabian Peninsula

ABSTRACT

Like many universities in the West, universities across the Arabian Peninsula are increasingly home to various conspicuous sustainability initiatives. This article examines this trend at three of the region’s most prominent projects: NYU-Abu Dhabi in the Emirates, Qatar Foundation’s Education City, and Saudi Arabia’s King Abdullah University of Science and Technology. Based on the textual analysis and informed by fieldwork in these countries since 2012, this article joins interdisciplinary research in political geography, sustainability experimentation, and laboratory studies to understand their iconic campuses not as enclaves, but as “exemplars” of sustainability and renewable energy futures in the region. Tracing their effects beyond their walls, I argue that they have mostly been limited to symbolically injecting sustainability into public discourse. While more substantial shifts toward sustainable development in the region are underway, these have largely stemmed from market forces rather than a new environmental consciousness promoted by these three iconic universities.     

Rock warming and drying under simulated intertidal conditions,part I: experimental procedures and comparisons with field data

The wetting–drying and warming–cooling behaviours of rock and stone are known to influence the nature and rate of weathering. The way materials warm‐up and dry‐out also influences their suitability as biological substrata. While rock thermal behaviours have been measured under controlled laboratory conditions, previous experiments have largely been restricted to terrestrial simulations due to practical constraints. Where efforts have been made to simulate intertidal conditions, expansion and contraction of rocks or rates of breakdown (i.e. sediment production and weight loss) have been measured, while detailed observations of thermal and drying behaviours have rarely been made. A simple, semi‐automated procedure is described that enabled measurement of surface temperatures and desorption (evaporative water loss) for different material types (rock and concrete) under simulated semidiurnal tide conditions. Some preliminary results are presented illustrating the types of data that were obtained, and comparisons are made with temperature data collected on a rock platform in the UK to assess the ability of the procedure to adequately represent field conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermal desorption of water ice in the interstellar medium

Water (H₂O) ice is an important solid constituent of many astrophysical environments. To comprehend the role of such ices in the chemistry and evolution of dense molecular clouds and comets, it is necessary to understand the freeze-out, potential surface reactivity and desorption mechanisms of such molecular systems. Consequently, there is a real need from within the astronomical modelling community for accurate empirical molecular data pertaining to these processes. Here we give the first results of a laboratory programme to provide such data. Measurements of the thermal desorption of H₂O ice, under interstellar conditions, are presented. For ice deposited under conditions that realistically mimic those in a dense molecular cloud, the thermal desorption of thin films (≪50 molecular layers) is found to occur with zeroth-order kinetics characterized by a surface binding energy, E _des, of 5773 ± 60 K, and a pre-exponential factor, A , of 10^30 ± 2 molecules cm⁻² s⁻¹. These results imply that, in the dense interstellar medium, thermal desorption of H₂O ice will occur at significantly higher temperatures than has previously been assumed.     

上海市检测中心实验室楼宇自控技术的应用

总结了上海市检测中心各种实验室内楼宇自控系统的应用,对普通舒适性新风机组、空调机组以及高精度空调机组等机组的监控原理做了详细比较分析。     

High-velocity dust collisions: forming planetesimals in a fragmentation cascade with final accretion

In laboratory experiments we determine the mass gain and loss in central collisions between centimetre- to decimetre-size SiO₂ dust targets and submillimetre- to centimetre-size SiO₂ dust projectiles of varying mass, size, shape and at different collision velocities up to ∼56.5 m s⁻¹. Dust projectiles much larger than 1 mm lead to a small amount of erosion of the target but decimetre targets do not break up. Collisions produce ejecta, which are smaller than the incoming projectile. Projectiles smaller than 1 mm are accreted by a target even at the highest collision velocities. This implies that net accretion of decimetre and larger bodies is possible. Independent of the original size of a considered projectile, after several collisions, all fragments will be of submillimetre size which might then be (re)accreted in the next collision with a larger body. The experimental data suggest that collisional growth through fragmentation and reaccretion is a viable mechanism to form planetesimals.