矿用预应力钢棒力学性能试验研究

预应力钢棒具有预紧力等级高、延伸率高、受力状态好等优点,越来越广泛地应用于煤矿巷道支护工程中。为了进一步探究矿用预应力钢棒材料力学性能,在实验室进行了矿用预应力钢棒拉伸试验、金相组织分析、冲击韧性测试、预应力损失试验、偏载试验、安装推进阻力试验及配套锁具性能试验。结果表明:直径20 mm矿用预应力钢棒拉伸时极限承载能力为422 kN,与直径20 mm、牌号HRB335锚杆杆体相比,增幅达176%,断后伸长率平均为13.3%,为锚索断后伸长率的2.4倍,断后呈杯锥状断口;钢棒拉断前后冲击吸收功分别为46.0 J和23.3 J,材料组织结构为回火索氏体,晶粒度为9.5和8.5,属于超细晶粒度;受力长度为1 230 mm和1 500 mm时,预应力损失为38.37%,和36.74%,随着载荷的加大,预紧力损失率减小;受力长度的增加,钢棒预紧力损失率减小;偏载角度为5°、10°、15°、20°及25°时,极限承载能力降幅分别为18. 3%、22. 5%、26. 4%、26. 9%及27. 5%;采用28 mm钻孔时,直径18 mm和直径20 mm钢棒平均最大推进阻力分别为179 N和453 N,两者相差274 N,但两者推进均比较容易;预应力钢棒锚具平均承载能力为398.2 kN,锚环与夹片的洛氏硬度分别为27.78和58.39,能够满足国标和钢棒材料力学性能要求。     

大跨度厚层泥岩复合顶板煤巷预应力组合支护

针对新元煤矿D302回风顺槽的大跨度厚层泥岩复合顶板,应用了高预应力桁架锚索联合控制技术。同时运用FLAC数值模拟软件对技术方案进行研究,确定了有效控制巷道围岩稳定性的总体布置方式,从而有效地控制巷道围岩塑性区和破碎区的发育,提高了围岩的承载能力。     

45 MN 双动反向挤压机生产线及其主要技术特点

本公司从德国SMS公司引进一条45MN双动反向挤压机生产线。就45MN双动反向挤压机生产线的配置、主要技术特点进行了简要的论述，为今后引进技术的消化吸收和实际生产打下良好的基础。     

福州八中屋面大型运动场超长建筑不设缝的技术和施工措施

本文通过混凝土温度应力的成因及后果分析,介绍了超长建筑不设缝的各种技术和施工措施,并在实际工程中应用,取得了良好的效果。     

无粘结竖向预应力粗钢筋在斜拉桥及连续箱粱中的应用讨论与施工技术

对某特大桥工程应用无粘结竖向预应力粗钢筋进行理论探讨；论述了预应力桥梁结构中竖向采用无粘结预应力高强粗钢筋的受力性能，抗裂性能，安全可靠性较有粘结预应力同样能满足设计要求，且施工简便，进度加快，节约工程造价。介绍了预应力体系与设置，竖向预应力粗钢筋的组成，施工技术，施工处理措施及质量控制。     

大跨度梁拱组合式渡槽关键施工技术

南水北调工程中线李村北干渠渡槽为梁拱组合式渡槽，总计分十二个阶段建成，过程控制复杂。施工期间，结合现浇梁段布置，将预应力张拉分三个阶段完成，逐步施加预应力。底模支撑以土胎膜为主，碗扣架为辅，可充分适应复杂结构特点。后期卸载时根据体系转换的要求，遵循对称均衡的原则，分四阶段完成，全面实现了设计意图。     

Anti-symmetric motion of a pre-stressed incompressible elastic layer near shear resonance

A two-dimensional model is derived for anti-symmetric motion in the vicinity of the shear resonance frequencies in a pre-stressed incompressible elastic plate. The method of asymptotic integration is used and a second-order solution, for infinitesimal displacement components and incremental pressure, is obtained in terms of the long-wave amplitude. The leading-order hyperbolic governing equation for the long-wave amplitude is observed to be not wave-like for certain pre-stressed states, with time and one of the in-plane spatial variables swapping roles. This phenomenon is shown to be intimately related to the possible existence of negative group velocity at low wave number, i.e. in the vicinity of shear resonance frequencies.     

Poling Conditions of Pre-Stressed Piezoelectric Actuators and Their Displacement

The poling procedure has always been the key issue in producing piezoelectric actuators with optimised performance. This is also true with the relatively new category of pre-stressed bender actuators, where mechanical bias achieved with a passive layer is introduced in the actuators during manufacturing. Due to these factors, the behaviour of the actuator under poling is different compared to its bulk counterparts. In this paper, two different thicknesses of commercial PZT 5A and PZT 5H materials were used in bulk actuators and pre-stressed benders realised by new method. Pre-stress was introduced by using a post-fired biasing layer utilising sintering shrinkage and difference in thermal expansion. The hysteresis loop of the actuators was measured under 0.5–7.0 MV/m electric fields at 25–125^∘C temperatures, providing information about their remnant polarisation and coercive field before poling. The results showed that high electric field and 25^∘C temperatures in poling provided higher remnant polarisation and coercive electric field than using 125^∘C temperature at poling. Difference was especially significant in coercive electric field values where up to 114.8% difference was obtained for PZT 5H bulk actuator and 65.9% for pre-stressed actuators. Higher coercive fields can be utilized as increased operating voltage range of piezoelectric devices. The differences in results obtained here and by others can be explained by the different pre-stress level, stronger clamping of the thicker passive layers of the RAINBOW and THUNDER actuators and passive ring area introducing high tensile stresses. The same conditions were used to pole the actuators, after which the displacement and dielectric constant of the actuators were measured. The displacement measurements showed that remnant polarisation has good correlation with displacement. This fact can be used in estimating pre-stressed actuator performance before actual poling. The dielectric constant measurements with a small signal after poling gave even better correlation than the remnant polarisation.     

斧子口水利枢纽左岸边坡加固方案及施工

介绍了斧子口水利枢纽左岸边坡在开挖过程出现的深层贯穿性裂缝及浅层洞隙问题,分析了裂缝滑塌的原因,根据揭露后的边坡地质结论和建议,提出了边坡的加固处理方案,并介绍了边坡加固的施工过程。     

软岩巷道锚杆支护技术模拟研究

软岩巷道支护一直是一个难以彻底解决的问题,利用计算机数值模拟分析方法,对在软岩巷道中影响锚杆支护效果的预应力、支护方式、锚杆长度及位置等方面内容进行了计算机模拟对比分析,得出使用锚杆支护时适合软岩掘进巷道相关参数的选择方法,从而利用分析结果指导工程实践。