Rock characterization while drilling and application of roof bolter drilling data for evaluation of ground conditions

Despite recent advances in mine health and safety, roof collapse and instabilities are still the leading causes of injury and fatality in underground mining operations. Improving safety and optimum design of ground support requires good and reliable ground characterization. While many geophysical methods have been developed for ground characterizations, their accuracy is insufficient for customized ground support design of underground workings. The actual measurements on the samples of the roof and wall strata from the exploration boring are reliable but the related holes are far apart, thus unsuitable for design purposes. The best source of information could be the geological back mapping of the roof and walls, but this is disruptive to mining operations, and provided information is only from rock surface.Interpretation of the data obtained from roof bolt drilling can offer a good and reliable source of information that can be used for ground characterization and ground support design and evaluations. This paper offers a brief review of the mine roof characterization methods, followed by introduction and discussion of the roof characterization methods by instrumented roof bolters. A brief overview of the results of the preliminary study and initial testing on an instrumented drill and summary of the suggested improvements are also discussed.     

保温材料导热系数测试数据复现性优化研究

针对不同类型、不同规格保温材料导热系数的差异性,对比试验了不同导热系数测试设备的复现性,研究了冷热板平均温度、冷热板温差、实验室温度、干燥工艺等因素对导热系数测试结果的影响;提出了导热系数测试结果准确性和复现性的相关措施。经实验室比对验证,优化效果明显。     

Determination of the thermal conductivity from physico-mechanical properties

Samples of limestone, dolomite, dolomitic limestone, marble, travertine, sandstone, siltstone, andesite, basalt and porous basalt from different parts of Turkey were tested to obtain their UCS, porosity, water absorption, density, P-wave velocity and thermal conductivity (TC). It was observed that while TC increased with density, P-wave velocity and UCS, it decreased with increasing porosity. Equations are presented to allow an assessment of TC from these physico-mechanical properties.      

The calculation of thermal conductivity and thermal diffusivity from transient heating measurements

Transient flow methods of measuring thermal conductivity and diffusivity often involve the extraction of the desired results from mathematical equations which are in the form of infinite series. This could be quite tedious without the aid of a computer. In this paper it is described how, in a particular instance, the results may be more easily obtained from a simple straight-line graph.     

Thermal conductivity from core and well log data

The relationships between thermal conductivity and other petrophysical properties have been analysed for a borehole drilled in a Tertiary Flysch sequence. We establish equations that permit us to predict rock thermal conductivity from logging data. A regression analysis of thermal conductivity, bulk density, and sonic velocity yields thermal conductivity with an average accuracy of better than . As a second step, logging data are used to compute a lithological depth profile, which in turn is used to calculate a thermal conductivity profile. From a comparison of the conductivity–depth profile and the laboratory data, it can be concluded that thermal conductivity can be computed with an accuracy of less than from conventional wireline data. The comparison of two different models shows that this approach can be practical even if old and incomplete logging data are used. The results can be used to infer thermal conductivity for boreholes without appropriate core data that are drilled in a similar geological setting.     

Equivalent thermal parameters from measured data

The experimental Norris Cotton federal office building in Manchester, New Hampshire, USA, was deliberately designed to test various energy-efficient systems. Monitoring and analysis has been extensive. Here, a member of the Center for Building Technology, US National Bureau of Standards, explains how equivalent thermal parameters were effectively determined from actual measured data, a technique which enables relatively simple measurements to provide approximate dynamic heat transfer coefficients.     

绝热材料低温导热系数的测试

采用防护热平板法进行绝热材料低温导热系数测试,测试实践解决了4个关键试验条件：测试堆的制冷、冷却水套及其管路中残留水的清除、冷凝水的去除和隔热、外防护套的配置。通过对国家标准参比低温导热系数的测试,结果表明：采用防护热平板法测试结果得出的导热系数方程与《绝热材料导热系数参比板》国家标准样品证书提供的导热系数方程吻合得很好,并认为将此方程外推至－60－0℃的数据可以作为校准导热仪的参考值。     

地源热泵岩土热物性现场测试方法评价

在总结地下岩土热物性现场测试方法的理论模型和算法的基础上,通过建立地源热泵系统的三维数值模型,构建了一个虚拟的标准地质孔,模拟得到了热响应曲线.采用常用的3种岩土热物性测试方法对标准地质孔的热物性参数进行了辨识,结果表明,与柱热源模型相比,基于线热源模型的2种测试方法具有较高的计算精度.     

Estimation of thermal conductivity of cemented sands using thermal network models

Effective thermal conductivity of soils can be enhanced to achieve higher efficiencies in the operation of shallow geothermal systems.Soil cementation is a ground improvement technique that can increase the interparticle contact area,leading to a high effective thermal conductivity.However,cementation may occur at different locations in the soil matrix,i.e.interparticle contacts,evenly or unevenly around particles,in the pore space or a combination of these.The topology of cementation at the particle scale and its influence on soil response have not been studied in detail to date.Additionally,soils are made of particles with different shapes,but the impact of particle shape on the cementation and the resulting change of effective thermal conductivity require further research.In this work,three kinds of sands with different particle shapes were selected and cementation was formed either evenly around the particles,or along the direction parallel or perpendicular to that of heat transfer.The effective thermal conductivity of each sample was computed using a thermal conductance network model.Results show that dry sand with more irregular particle shape and cemented along the heat transfer direction will lead to a more efficient thermal enhancement of the soil,i.e.a comparatively higher soil effective thermal conductivity.     

岩土热物性热响应测试的试验研究

通过测试装置测定出测试孔输入功率、环路平均温度,采用线热源模型对现场测试数据进行推导分析,计算出测试孔岩土导热系数,该数值对在当地以及周边地区进行土壤源热泵系统设计具有重要的参考价值。     

Effective thermal conductivity of vacuum insulation panels

Vacuum insulation panels (VIPs) with evacuated fumed silica as the core material and different barrier envelopes were subjected to a series of tests in a guarded hot plate apparatus. The process was conducted to determine thermal conductivity at the centre-of-panel and the edge effect, i.e. the linear thermal transmittance due to the thermal conductivity of the barrier envelope, which is many orders of magnitude higher than that of the evacuated fumed silica. Numerical simulations using a two-dimensional model were carried out in parallel and compared with measured results. In a further step, the influences of different parameters such as panel size, metal layers in the barrier envelope and the shape of the joint between two adjacent VIPs were quantified. Based on these findings, an effective thermal conductivity can be attributed to a system of VIPs. Investigations were performed within the framework of an international research programme of the IEA, Annex 39 'High Performance Thermal Insulation in Buildings and Building Systems', Subtask B.     

Effective thermal conductivity of vacuum insulation panels

Vacuum insulation panels (VIPs) with evacuated fumed silica as the core material and different barrier envelopes were subjected to a series of tests in a guarded hot plate apparatus. The process was conducted to determine thermal conductivity at the centre-of-panel and the edge effect, i.e. the linear thermal transmittance due to the thermal conductivity of the barrier envelope, which is many orders of magnitude higher than that of the evacuated fumed silica. Numerical simulations using a two-dimensional model were carried out in parallel and compared with measured results. In a further step, the influences of different parameters such as panel size, metal layers in the barrier envelope and the shape of the joint between two adjacent VIPs were quantified. Based on these findings, an effective thermal conductivity can be attributed to a system of VIPs. Investigations were performed within the framework of an international research programme of the IEA, Annex 39 ‘High Performance Thermal Insulation in Buildings and Building Systems’, Subtask B.     

建筑用绝热材料导热系数的测试及其应用

介绍了建筑用绝热材料的含义,从材料生产、节能设计、工程施工、试验检测、管理等阶段,分析了建筑用绝热材料导热系数在测试与应用中需改进的一些问题,以真正实现节能减排的目标。     

轻质保温墙体导热系数现场测试的研究

墙体保温是实现建筑节能的一项重要措施。现场实测是判定墙体是否保温的有力手段,进一步开发建筑热工性能检测技术也是我国未来建筑节能工作的一个重点。利用防护热板法对轻质保温墙体导热系数进行了现场测试,通过数值分析和实验,并进行了对比测试,证明了该方法应用于此类墙体热工性能测试的可行性。     

一种测试建筑隔热涂料导热系数的方法

减少建筑能耗是工程领域的一个重要课题,评价节能效果的方法尤为重要。对于建筑隔热涂料,导热系数是评价其隔热性能的重要指标,其准确测试对于建筑隔热涂料评价、节能效果预测、新涂料研制开发等有重要意义。本文通过理论推导得到一种简便的涂料导热系数评价方法,并选取样品进行了验证。     

Automatic classification of urban ground elements from mobile laser scanning data

Accessibility diagnosis of as-built urban environments is essential for path planning, especially in case of people with reduced mobility and it requires an in-depth knowledge of ground elements. In this paper, we present a new approach for automatically detect and classify urban ground elements from 3D point clouds. The methodology enables a high level of detail classification from the combination of geometric and topological information. The method starts by a planar segmentation followed by a refinement based on split and merge operations. Next, a feature analysis and a geometric decision tree are followed to classify regions in preliminary classes. Finally, adjacency is studied to verify and correct the preliminary classification based on a comparison with a topological graph library. The methodology is tested in four real complex case studies acquired with a Mobile Laser Scanner Device. In total, five classes are considered (roads, sidewalks, treads, risers and curbs). Results show a success rate of 97% in point classification, enough to analyse extensive urban areas from an accessibility point of view. The combination of topology and geometry improves a 10% to 20% the success rate obtained with only the use of geometry.     

Relating thermal conductivity of soil skeleton with soil texture by the concept of“local thermal conductivity fluctuation”

The thermal conductivity of the soil skeletonλ;is an essential parameter from the point of view of the correct assessment of soil overall/effective conductivity.This work introduces the concept of“local thermal conductivity fluctuation”which characterizes the microscale variation of conductivity within the solid phase.It is proposed to link the“local fluctuation”of thermal conductivityλwith the soil texture-the information that is available at the scale of engineering applications.It was possible to relate the skeleton thermal conductivity with the grain size distribution of the soil.Finally,based on a large series of numerical simulations,the paper provides four triangle diagrams(at different organic matter contents:0%,2%,4%and 6%)relating the value ofλ;with volume fraction of individual soil separates.This result is extremely important from the practical point of view.One can quickly evaluateλ;value provided that information on the grain size distribution and organic matter content is available.     

On the effective thermal conductivity of building bricks

This study contains computational and experimental investigation of the effective thermal conductivity of porous type building bricks. Internal heat transfer (conduction, convection and radiation) is considered in the numerical study under steady state condition. Experiments have been conducted to compare the numerical results with the experimental ones. Practical formulae are obtained and presented for a realistic estimation of the effective thermal conductivity of the building bricks. Present formulations include the effect of all of the parameters of the heat transfer mechanisms.