Estimating the uniaxial compressive strength of pyroclastic rocks from the slake durability index

Because the preparation of standard samples may not always be possible for weak or soft rocks, the prediction of uniaxial compressive strength (UCS) from indirect methods is widely used for preliminary investigations. In this study, the possibility of predicting UCS from the slake durability index (SDI) was investigated for pyroclastic rocks. For this purpose, pyroclastic rocks were collected from 31 different locations in the Cappadocian Volcanic Province of Turkey. The UCS and SDI tests were carried out on the samples in the laboratory. The UCS values were correlated with the SDI values and a very strong exponential relation was found between the two parameters. Since some data were scattered over the UCS values of 20 MPa, the correlation plot was redrawn for above and below the UCS values of 20 MPa, respectively. Very strong linear correlations were developed for two cases. Our concluding remark is that the UCS of pyroclastic rocks can be estimated from the SDI.

     

A discrete model for prediction of radon flux from fractured rocks

Prediction of radon flux from the fractured zone of a propagating cave mine is basically associated with uncertainty and complexity. For instance, there is restricted access to these zones for field measurements, and it is quite difficult to replicate the complex nature of both natural and induced fractures in these zones in laboratory studies. Hence, a technique for predicting radon flux from a fractured rock using a discrete fracture network (DFN) model is developed to address these difficulties. This model quantifies the contribution of fractures to the total radon flux, and estimates the fracture density from a measured radon flux considering the effects of advection, diffusion, as well as radon generation and decay. Radon generation and decay are classified as reaction processes. Therefore, the equation solved is termed as the advection-diffusion-reaction equation (ADRE). Peclet number (Pe), a conventional dimensionless parameter that indicates the ratio of mass transport by advection to diffusion, is used to classify the transport regimes. The results show that the proposed model effectively predicts radon flux from a fractured rock. An increase in fracture density for a rock sample with uniformly distributed radon generation rate can elevate radon flux significantly compared with another rock sample with an equivalent increase in radon generation rate. In addition to Pe, two other independent dimensionless parameters (derived for radon transport through fractures) significantly affect radon dimensionless flux. Findings provide insight into radon transport through fractured rocks and can be used to improve radon control measures for proactive mitigation.     

Application of neural networks for the prediction of the unconfined compressive strength (UCS) from Equotip hardness

This paper presents the application of a neural network for the prediction of the UCS from hardness tests on rock samples. To investigate the suitability of this approach, the results of the network are compared to predictions obtained by conventional statistical relations.The network was trained to predict the UCS based on the hardness, porosity, density, grain size and rock type information of a rock sample. A dataset containing 194 rock sample records, ranging from weak sandstones to very strong granodiorites, was used to train the network with the Levenberg–Marquardt training algorithm. Two sets, each containing 17 rock samples, were used to validate the generalization and prediction capabilities of the network.     

Performance of pyroclastic rocks from Abakaliki Metropolis (southeastern Nigeria) in road construction projects

A total of 15 samples from the Abakaliki pyroclastic rock bodies were subjected to petrographic and mechanical analyses to determine the suitability of the rock type as a road aggregate. Results indicate that the Abakaliki pyroclastic rock yield aggregates with marginal performance in road projects. Although the aggregates meet a number of road stone requirements (i.e., ten percent fines and their ability to absorb water), they fail to meet other key road stone requirements. Whilst their aggregate impact values, Los Angeles abrasion values, and flakiness index are generally above the recommended limits, petrographic analyses reveal appreciable amounts of shaley to muddy lithic fragment and volcanic glassy groundmass. These detrimental constituents and marginal laboratory test results would likely translate to long term poor field performance where the pyroclastic aggregate is used for road construction. This study suggests that utilization of the Abakaliki pyroclastic rock as an aggregate, especially for road construction, requires informed caution, particularly when the material is exposed to climatic extremes (high volume of rainfall and high and fluctuating temperature) as is the case in the tropics.     

A preliminary study of assimilating numerical weather prediction data into computational fluid dynamics models for wind prediction

The goal of this effort is to combine the strengths of Numerical Weather Prediction (NWP) with Computational Fluid Dynamics (CFD) to produce locale-specific flow patterns that could be used for micrositing wind power plants. We do this in two ways: (1) we use the mesoscale model data as inflow for the CFD model and (2) we assimilate vertical profiles of mesoscale model output into the CFD model as a body force. We study the impact of this technique with a case study in the rolling topography of central Pennsylvania. We compare wind profiles between the mesoscale model alone, the CFD model alone, and the fully assimilated mesoscale/CFD solution. In addition, we examine the impact of the mesoscale assimilation into the CFD model on the fine-scale flow structure. This preliminary approach of combining techniques in NWP and CFD through data assimilation provides a unique assessment of the utility of specific locations for wind power production as well as for improving simulations for other purposes.     

多项式分布滞后模型在桥梁挠度预测中的应用

介绍了PDL(多项式分布滞后)模型,并将其应用于某桥梁挠度预测,重点考虑了温度以及车流量对挠度的影响。借助EVIEWS软件对桥梁不同时期的挠度变形值进行预测,并与灰色GM(1,1)模型的预测结果进行对比分析。结果表明,PDL模型具有比灰色模型更高的预测精度,其预测结果更为可靠,对类似工程有一定的借鉴作用。     

A preliminary coupled MT-GA model for the prediction of highway runoff quality

Pollutants accumulated on road pavement during dry periods are washed off the surface with runoff water during rainfall events, presenting a potentially hazardous non-point source of pollution. Estimation of pollutant loads in these runoff waters is required for developing mitigation and management strategies, yet the numerous factors involved and their complex interconnected influences make straightforward assessment impossible. Data-driven models (DDMs) have lately been used in water and environmental research and have shown very good prediction ability. The proposed methodology of a coupled MT-GA (model tree-genetic algorithm) model provides an effective, accurate and easily calibrated predictive model for EMC (event mean concentration) of highway runoff pollutants. The models were trained and verified using a comprehensive data set of runoff events monitored in various highways in California, USA. EMCs of Cr, Pb, Zn, TOC and TSS were modeled, using different combinations of explanatory variables. The models' prediction ability in terms of correlation between predicted and actual values of both training and verification data was mostly higher than previously reported values. Sensitivity analysis was performed to examine the relative significance of each explanatory variable and the models' response to changes in input values.     

建设项目用地预审管理办法

《建设项目用地预审管理办法》,已经2004年10月29日国土资源部第9次部务会议修订通过,现将修订后的《建设项目用地预审管理办法》公布,自2004年12月1日起施行。 部长孙文盛二○○四年十一月一日     

用户体验视角下的体育馆使用后评价指标初探

借鉴产品设计领域的用户体验设计思路,以现有的体育建筑使用后评价指标为基础,通过搜集分析场馆网络点评数据,初步探索建立用户体验视角下的体育馆使用后评价指标体系.     

南京市新就业大学生青年公寓租住体验研究

通过实地调研发现南京现有青年公寓风格多样、活动丰富,基本能够满足新就业大学生生活品质、社会交往等方面的需求,但同时也存在卫生堪忧、安全不佳等问题。指出目前市场上青年公寓质量参差不齐,地方政府应在鼓励其发展的同时加强监管,为新就业大学生创造扎根的可能。     

A study on carbonation depth prediction for fly ash concrete

Carbonation of fly ash concrete is studied by using two types of fly ash with different CaO contents. It is observed that under natural exposure environments, the carbonation rate is the highest when specimens are exposed in the city. The decreased ratio of water to binder and fly ash content leads to a better carbonation resistance. For the same fly ash content, specimens of high-CaO fly ash show a better carbonation resistance than those of low CaO fly ash. However, when compared at an equal strength, the effect of the type of fly ash on carbonation becomes insignificant. When comparing the carbonation results of concrete and mortar specimens, results of mortar show similar trends as those of concrete. However, the test results on mortar are worse by the use of fly ash than those of concrete. In addition, the carbonation tests in an accelerated environment are also conducted. It is found that there exist strong relations between carbonation depths of concrete exposed in natural and in accelerated environments. A mathematical approach to predict the carbonation depth in the natural environments is proposed based on the accelerated tests and the square-root-t-law.     

力学实验教学改革的初步探究

以西安建筑科技大学力学实验中心为例,从转变教学管理观念、活用多媒体教学手段、增设开放性实验、完善考评机制四个方面对力学实验教学改革进行了探讨,对提高教学质量有着重要意义。     

Comprehensive prediction of rockburst based on analysis of strain energy in rocks

Strain energy is a key factor of inducing rockburst in mine. The occurrence of rockburst depends not only on the property of storing strain energy in rocks, but also on the environment of strain energy accumulation in mining. This investigation has been carried out on the property of strain energy stored in rocks by experiment and of which distributed around the mining pits of Linglong gold mine in China by using three-dimensional numerical modeling. In comparison with the pre-existing criteria of rockburst in literature, a comprehensive prediction of rockburst has been made so far as the ores are extracted at the depth of −570 m. The study shows that strain energy analysis with the aid of numerical modeling is useful in prediction of rockburst.     

A comparative study of stress influence on fracture apertures in fragmented rocks

This study compares the calculated fracture apertures in a fragmented rock layer under different stress scenarios using two different approaches. Approach 1 is a simplified method using a two-dimensional (2D) mapping of the fracture network and projects the far-field stresses to individual fractures, and calculates the dilation, normal and shear displacements using experimental stiffnesses available in the literature. Approach 2 employs a three-dimensional (3D) finite element method (FEM) for the mechanical analysis of the fragmented rock layer considering the interaction with the neighbouring rock layers, frictional interfaces between the rock blocks, stress variations within the fragmented rock layer, and displacements, rotations and deformations of rock blocks. After calculating the fracture apertures using either of the approaches, the permeability of the fragmented rock layer is calculated by running flow simulations using the updated fracture apertures. The comparison between the results demonstrates an example of the inaccuracies that may exist in methods that use simplified assumptions such as 2D modelling, ignoring the block rotations and displacements, projected far-field stresses on fractures, and the stress variations within the rock layer. It is found that for the cases considered here, the permeability results based on apertures obtained from the simplified approach could be 40 times different from the results from apertures calculated using a full mechanical approach. Hence, 3D mechanical modelling implementing realistic boundary conditions, while considering the displacements and rotations of rock blocks, is suggested for the calculation of apertures in fragmented rocks.     

房地产高周转模式之初探

通过研究目前高周转模式的现状,简要分析了高周转模式的误区以及其运转的五个要点,并在分析高周转模式的基础上,对标准化模式进行了探究并简单阐述了高周转标准化模式的必要性。     

浅谈节约型屋顶绿化设计

当前,经济的快速发展使人们也希望有一个舒适的生活环境。屋顶绿化是人们生活环境的一部分,并逐渐被社会各界认识和接受,将会为中国的城市建设做出巨大贡献。本文针对当前传统屋顶绿化存在的成本高、资源过渡浪费、养护管理难度大等普遍问题,提出了节约型屋顶绿化的概念。并在此基础上进一步总结了其特点,对适用于当代中国的节约型屋顶绿化做...     

Determining the damping factor of sedimentary rocks required for seismically designed structures

Relationships for the shear damping ratio D_s (a function of shear quality factor Q_s) and modulus decay curve G_seis/G_max as a function of shear strain for mudrocks have been developed. Field experiments to determine damping ratio and elastic moduli should be performed at frequencies as close as possible to the bandwidth (0–100 Hz) of interest for building design. Estimates of these parameters made from extrapolating laboratory core (MHz) or wireline (kHz) data to lower frequencies can be highly unreliable. Field estimates of damping ratio are very dependent on, and often totally dominated by, the effects of scattering of P and S waves by inhomogeneities in the rock mass structure. This is, particularly, the case when open fractures or cracks are present in near-surface rocks.     

工程项目数字化管理初探

随着工程项目的建设规模日趋庞大、复杂,传统的项目管理方法已经越来越不能适应项目建设的要求,新兴的数字化技术则为工程项目管理提供了新的手段,而且也将成为工程项目管理领域发展的必然趋势。重点分析了工程项目数字化管理的内涵及可能实现的手段,旨在引起更多的对数字化管理的进一步探讨。     

浙江采石文化的初步研究

浙江采石文化具有鲜明的地域特色,是乡土文化的组成部分。浙江采石活动历史悠久,古代采石遗迹分布广泛。采石文化从属于石文化体系,具有独特的内涵和价值。从采石对象、采石方式、采石场所、采石动机和采石历史等五个方面对浙江采石文化予以探讨,可以丰富区域文化的研究内容。     

浅析淮海经济区发展

本文首先界定了淮海经济区的范围,从经济、产业发展等多个方面分析了淮海经济区在我国的重要地位及其发展中存在的主要问题．在此基础上分别探讨了构建徐州都市圈与淮海省的可能性与条件,最后提出了加速淮海经济区发展的一些具体措施。