打钻揭高瓦斯煤层常见问题的处理

打钻过程中揭高瓦斯煤层，常常遇到打夹矸、喷孔、卡钻、掉钻等问题，严重的还能诱发瓦斯喷出。兴山煤矿在多年的打钻工作中，积累了一定经验，能够较好的保证钻孔钻进的进度。     

打钻揭高瓦斯煤层常见问题的处理

打钻过程中揭高瓦斯煤层，常常遇到打夹矸、喷孔、卡钻、掉钻等问题，严重的还能诱发瓦斯喷出。兴山煤矿在多年的打钻工作中，积累了一定经验，能够较好的保证钻孔钻进的进度。     

光缆线路施工维护中常见问题及处理

随着矿区通信业务的发展,固话业务通讯局站间的中继线路,数据业务传输网络已被光缆所取代,现代通信业务的传输主要依靠光缆。目前,我局以建成各类型数据传输网络累计达近五百公里,确保通信传输质量尤为重要。因此,结合我矿区通信的实际生产情况,对光缆线路实际施工维护中常见的一些问题加以简述,以及如何处理问题的方法进行探讨。     

吊顶施工过程中常见问题及处理方法

理论联系实践,探讨了吊顶施工中常见问题原因,认为能否有效的控制好施工进度是一个企业是否有利润的关键前提。     

工业产品生产许可证现场实地核查中常见问题及其解决方法探讨

在工业产品生产许可证现场实地核查工作中,经常会碰到各种各样问题,有些与教程中曾经给出的示例相类似,也有一些是教程中未曾提到过的,还有一些甚至是不带有普遍性的个案,审查员在现场实地核查时如何准确把握这些问题,如何正确处理并给出准确结论,笔者根据自身工作体会,对审查工作中经常遇到的问题进行了总结,并提出解决建议,希望与各方审查员相互学习深入讨论。     

商品混凝土裂缝成因和防控处理探讨

混凝土裂缝现象在建筑工程施工中极为常见的现象,它的出现也影响到工程施工的质量。本文就商品混凝土温度裂缝产生机理特征,提出了具体预防措施和裂缝出现后的处理方法。     

针对桥梁施工中常见问题的处理

桥梁工程的质量问题、施工问题、裂缝问题以及其自身的养护问题都成为了当今制约我国道路桥梁质量与安全的首要问题之一。本文针对这些问题的处理措施进行了阐述。     

混凝土外观质量处理方法

2008年金融危机爆发后,中国政府为刺激经济、扩大内需,四万亿元基础设施投资计划已全面启动,其中基础设施建设大部分工程离不开混凝土。本文从实践操作经验出发,就如何找到混凝土产生表面缺陷的内因,采取有针对性预防措施和修复处理进行分析。     

浅谈泵送商品混凝土浇筑裂缝产生原因及控制

<正>钢筋混凝土的裂缝控制问题是建筑工程中很重要的问题之一,特别是最近20年来,泵送商品混凝土获得广泛应用之后,混凝土质性有了很大改善的同时,裂缝控制技术难度大大增加了。     

谈混凝土裂缝的成因及预防措施和处理方法

大量的工程和实践理论分析表明，钢筋混凝土构件基本上都是带裂缝工作的，只是有些裂缝很细，一般对结构的使用无大的危害，允许其存在。有些裂缝在使用荷载或外界物理及化学因素作用下，不断产生和发展引起混凝土碳化、保护层剥落及钢筋锈蚀，使钢筋混凝土强度和刚度受到削弱，耐久性降低，严重时甚至发生垮塌事故，危害结构的正常使用，必须加以控制。     

预拌混凝土在生产施工中的若干问题

文章简洁的阐述了预拌混凝土在生产施工中经常能够遇到的实际问题和解决方法。     

影响预拌混凝土质量若干问题的探讨

本文通过对影响预拌混凝土质量若干问题的原因分析,探讨了目前影响预拌混凝土质量的主要因素,并提出了部分应对措施供参考,希望通过各方的共同努力提高预拌混凝土质量。     

Two-layer pre-stressed beams consisting of normal and steel fibered high strength concrete

The paper is focused on analysis of two-layer bending pre-stressed beams consisting of steel fibered (SF) high strength concrete (HSC) in compressed zone and normal strength concrete (NSC) in tensile zone. Investigation of such beams is important for RC structural design, because calculation of fibers volume ratio is significant, like that of reinforcing steel bars for usual RC elements. In other words, such elements are made of high performance concrete (HPC). There is a growing tendency that more effective HPC structures replace NSC ones, first of all in pre-stressed elements. Definition of the HSC class lower limit, to be used in the compressed zone of a two-layer pre-stressed beam, is given. It was demonstrated that SF have little effect on the beam elastic deflections. However, the ultimate deflections of the section increase because additional potential for plastic energy dissipation (PED) in the bending element. NSC, used in the section tensile zone, contributes additionally about 20% to the section’s PED potential compared to one-layer HSC beams. In order to guarantee sufficient section’s ductility of the pre-stressed beams, required to withstand dynamic loadings, a minimum SF ratio is proposed to be considered. The fibers take the tensile stresses, yielding cracks in the concrete matrix. A design method for calculation of the SF volume ratio, as a function of required ductility, is proposed. A numerical example, illustrating the efficiency of this method is presented.     

Constitutive modeling of creep-fatigue interaction for normal strength concrete under compression

Conventional approaches to model fatigue failure are based on a characterization of the lifetime as a function of the loading amplitude. The Wöhler diagram in combination with a linear damage accumulation assumption predicts the lifetime for different loading regimes. Using this phenomenological approach, the evolution of damage and inelastic strains and a redistribution of stresses cannot be modeled. The gradual degration of the material is assumed to not alter the stress state. Using the Palmgren–Miner rule for damage accumulation, order effects resulting from the non-linear response are generally neglected.In this work, a constitutive model for concrete using continuum damage mechanics is developed. The model includes rate-dependent effects and realistically reproduces gradual performance degradation of normal strength concrete under compressive static, creep and cyclic loading in a unified framework. The damage evolution is driven by inelastic deformations and captures strain rate effects observed experimentally. Implementation details are discussed. Finally, the model is validated by comparing simulation and experimental data for creep, fatigue and triaxial compression.     

Basis mapping methods for forward and inverse problems

This paper describes a novel method for mapping between basis representation of a field variable over a domain in the context of numerical modelling and inverse problems. In the numerical solution of inverse problems, a continuous scalar or vector field over a domain may be represented in different finite‐dimensional basis approximations, such as an unstructured mesh basis for the numerical solution of the forward problem, and a regular grid basis for the representation of the solution of the inverse problem. Mapping between the basis representations is generally lossy, and the objective of the mapping procedure is to minimise the errors incurred. We present in this paper a novel mapping mechanism that is based on a minimisation of the L² or H¹ norm of the difference between the two basis representations. We provide examples of mapping in 2D and 3D problems, between an unstructured mesh basis representative of an FEM approximation, and different types of structured basis including piecewise constant and linear pixel basis, and blob basis as a representation of the inverse basis. A comparison with results from a simple sampling‐based mapping algorithm shows the superior performance of the method proposed here. © 2016 The Authors. International Journal for Numerical Methods in Engineering Published by John Wiley & Sons Ltd.     

Algebraic multigrid methods for solving generalized eigenvalue problems

Three algebraic multigrid (AMG) methods for solving generalized eigenvalue problems are presented. The first method combines modern AMG techniques with a non‐linear multigrid approach and nested iteration strategy. The second method is a preconditioned inverse iteration with linear AMG preconditioner. The third method is an enhancement of the previous one, namely the locally optimal block preconditioned conjugate gradient. Efficiency and accuracy of solutions computed by these AMG eigensolvers are validated on standard benchmarks where part of the spectrum is known. In particular, the problem of isospectral drums is addressed. Copyright © 2005 John Wiley & Sons, Ltd.     

Finite element analysis of various methods for protection of concrete structures against spalling during fire

A mathematical model of hygro-thermo-mechanical phenomena in heated concrete, treated as multiphase porous material is briefly presented. Some modifications necessary to analyse high–temperature performance of a concrete containing the PP-fibres have been introduced, experimentally validated and applied for analysis of performance of a concrete tunnel lining during a 10-MW fire and the ISO standard fire. Three methods for protecting concrete structures against excessive degradation in fire conditions have been numerically analysed by means of the computer model. The analysed protection methods are based either upon application on a structure surface of a reflective layer, or covering it with a protective layer made of a very porous concrete or an addition of the PP fibres to the concrete mix. Efficiency of these methods has been numerically analysed in thermal conditions corresponding to the ISO-834 standard fire. The results obtained show that even relatively simple methods, like application a protective layer or increasing the surface reflectance, can retard to some extent concrete degradation during a fire.     

Comparison of numerical methods for the assessment of production availability of a hybrid system

A finite volume (FV) scheme is proposed in order to compute different probabilistic measures for systems from dynamic reliability field. The FV scheme is tested on a small but realistic benchmark case stemmed from gas industry [Labeau PE, Dutuit Y. Fiabilité dynamique et disponibilité de production: un cas illustratif. Proceedings of λμ 14, Bourges, France, vol. 2. 2004. p. 431–6 [in French]]. The point is to compute the production availability and the annual frequency of loss of nominal production (among other quantities) for a system of gas production. The results of the FV method are compared to those obtained by Monte Carlo simulation, showing the accuracy of the method.     

聚羧酸减水剂在机制砂商品混凝土应用中的敏感性评价

与天然砂相比．聚羧酸减水剂在机制砂商品泥凝土的应用中表现出了更高的敏感性对此，本文采用测试混凝上拌合物工作性能的方法．评价聚羧酸减水剂的敏感性，同时提出通过复配不同性能特点的聚羧酸产品来达到降低其在机制砂商品混凝土中应用的敏感性，提高聚羧酸综合性能的措施。     

氪、氙气生产的安全问题

根据多年来在稀有气体氪、氙系统操作中所发生的事故进行总结分析 ,提出了安全隐患的形成原因和防范措施