Effects of circumferential pick spacing on boom type roadheader cutting head performance

Effects of equal and unequal circumferential pick spacing on the performance of boom type roadheaders having cylindrical cutting heads are investigated. For this purpose, two experimental cutting heads with equal and unequal circumferential spacing are designed and manufactured. The cutting head with unequal circumferential spacing is specifically designed to prevent tool-holder overlap at the nose section. Manufacturing difficulties associated with equal circumferential pick spacing due to tool-holder overlap are discussed with solid modeling and practical applications. The heads are tested at Park Cayirhan Coal Mine in Turkey and their cutting performances are analysed. Although better cutting performance for equal circumferential spacing are predicted by force–balance analysis, in situ measurements of instantaneous (net) traversing speed and cutting rate, pick consumption rate and machine vibration show that no significant difference exists between the performances of the two cutting heads.     

Some geological and geotechnical factors affecting the performance of a roadheader in an inclined tunnel

The factors affecting the performance of 90 kW-shielded roadheader is investigated in detail in a tunnel excavated for Nuh Cement Factory. The first part of the tunnel is horizontal and the second part is inclined with 9° and excavated uphill. Tunnel passes through a formation of the Upper Cretaceous age with nodular marl, carbonated claystone, thin and thick laminated limestone. Water ingress changes from 0 to 11 l/min. In six different zones it is found that the rock compressive strength changed from 20 to 45 MPa, tensile strength from 1 to 4 MPa, specific energy from 11 to 16 MJ/m³, plastic limit from 15% to 29%, liquid limit from 27% to 43% and water absorption from 4% to 18% in volume.

Detailed in situ observations show that in dry zones for the same rock strength the inclination of the tunnel and the strata help to increase the instantaneous cutting rate from 10 to 25 solid bank m³/cutting hour. The effect of water on cutting rate is dramatic. In the zones where the plastic limit and the amount of Al₂O₃ is low, instantaneous cutting rate increases from 34 to 50 solid bank m³/cutting hour with increasing water content from 3.5 to 11 l/min. However, in the strata having high water absorption characteristic and high amount of Al₂O₃, cutting rate decreases considerably due to the sticky mud, causing problem to the cutterhead. Excavation, muck loading and support works are performed separately due to safety concerns in the wet and inclined sections which reduced the machine utilization time from 38% to 8%. The information gathered is believed to form a sound basis in contributing the performance prediction of roadheaders in difficult ground conditions.     

挤压式边墙技术在面板堆石坝工程中的应用

结合工程实例,提出了采用混凝土挤压式边墙护坡技术作为该电站面板堆石坝上游坡面施工的新方法,对挤压式边墙技术指标及施工方法进行了介绍,并阐述了挤压式边墙的施工特点,最后对其进行了质量检测,以推广该技术的应用。     

浴室干燥热泵热水器实验研究

设计了一款具有除湿功能的浴室干燥热泵热水器,分析了系统结构和工作原理。对不同运行模式的实验研究表明,该热水器在节能与功能方面具有独特的优势。     

Flexible design of a rock slope abutment at the Wuqiangxi Hydroelectric Power Station

This paper presents the results of the real-time monitoring of a rock slope at the abutment of the Wuqiangxi Hydroelectric Power Station, Hunan Province, China, and the ensuing modifications of the original design and excavation process. Monitoring sites were carefully selected based on information collected on geological features (for example, faults) and from the results of numerical modelling. A flexible approach to the design was taken, using feedback from the monitoring system which allowed (1) time to set up support/remedial measures during the work and (2) a reduction in the use of pre-stressed anchored cables. As a consequence, the work was successfully carried out with cost savings and no safety problems.

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Résumé Cet article présente les résultats d’auscultation d’une pente rocheuse au niveau d’ouvrages de soutènement pour la centrale hydroélectrique de Wuqiangxi (province de Hunan, Chine). Cette surveillance en temps réel a permis des modifications du projet initial et des procédés d’excavation. Les sites instrumentés ont été soigneusement choisis en fonction du contexte géologique et des failles présentes, tout en prenant appui sur des résultats de simulation numérique. Une conception d’ouvrage capable d’adaptation a été définie, utilisant les informations en retour de l’auscultation, ce qui a permis a) de mettre en oeuvre des mesures de soutènement en temps voulu et b) de limiter l’utilisation de câbles précontraints. En conséquence, les travaux ont été réalisés avec succès, des économies étant réalisées et les problèmes de sécurité maîtrisés.

     

旋风除尘器下降流量的研究

通过实验测定了常规旋风除尘器内下降流量铅高度的分布,发现在排气芯管入口断面附近有约２４％的短路流量,测定了安装不同类型减阻杆后的下降流量,发现非全长减阻杆下端固定时,有增加减阻杆上方断面下降流量的功效,这将延长含尘气流在除尘器内的停留时间,提高除尘效率。     

Experimental investigations on the crush behaviour of AA6061-T6 aluminum square tubes with different types of through-hole discontinuities

An experimental investigation was conducted to compare the crush characteristics and energy absorption capacity of AA6061-T6 aluminum alloy extrusions with centrally located through-hole discontinuities. Three different types of geometrical discontinuities, namely, circular, slotted and elliptical holes were fabricated into AA6061-T6 extrusions which had a length of 200 mm, nominal side width of 38.1 mm and wall thickness of 3.15 mm. Furthermore, three different major axis lengths (7.14, 10.72, and 14.29 mm) and three different aspect ratios (1.33, 2.0, and 3.0) of the slotted and elliptical discontinuities were considered. It was found that by introducing crush initiators into the structural members, a splitting and cutting deformation mode was generated rather than global bending deformation which was observed for specimens without any discontinuities. The peak crush load was reduced by incorporating the through-hole crush initiators within a range of 5.2–18.7%, and total energy absorption was increased within a range of 26.6–74.6%. The most significant improvement was noted in the crush force efficiency, which was increased within the range of 54.5–95.8%. For specimens with discontinuities which had a major axis length of 7.14 mm the peak crush load and total energy absorption was independent of initiator geometry and aspect ratio. However, for specimens which had discontinuities with a major axis length of 10.72 and 14.29 mm and an aspect ratio of 3, a geometrical influence on the peak crush load and total energy absorption was apparent.     

相同建筑相同节能措施在不同气象条件下的负荷减少率

以广州、重庆、北京等12个城市为对象,分别以DOE-2中的TMY2,DeST—h中的TRY及修改的TMY2辐射数据,构建了36组完全不同的8760h气象数据库。利用特征温度法模拟计算相同建筑在围护结构改进前后单位建筑面积的全年空调和供暖耗能量。研究发现,对所涉及的城市,尽管因三种气象数据库（36组）显著不同,导致计算出的围护结构改进前后（72组）建筑全年空调供暖负荷、负荷减小量存在很大的差异,但是在不同气象条件下对模型建筑采取相同的节能措施。各城市全年空调负荷减小率（节能率）是相近的;各个城市全年供暖负荷减小率（节能率）也是相近的。从而证明了现行各国标准均规定围护结构K限值的通常做法是完全正确的。     

某底层框架砖房的消能减震设计

研究了底层框架砖房采用消能减震技术的抗震设计方法,介绍了宿迁某底层框架砖房采用粘弹性阻尼器的消能减震设计,给出了多遇地震和罕遇地震作用下的主要计算结果。计算表明,设置粘弹性阻尼器后,上部结构在多遇、罕遇地震作用下均能满足承载力与变形的要求。     

Experimental analysis of control loops with different delay times in the supply air system of a radiator test rig

The test rig of low-temperature hot-water radiator is a typical multi-input multi-output (MIMO) thermal system with large time delay. Aiming at the control of the supply air temperature and the temperature of the environmental chamber in the test rig, the paper carries out the fuzzy control experiments and PI control experiments based on adjusting the electric heater in the supply air system, in which there are two control loops with various delay time. The experiments researched two types of fuzzy control methods which are the basic fuzzy control (BFC), and the self-organizing rules fuzzy control (SORFC) with zero initial control rules. For the control loop of supply air temperature with short delay time, PI control performs better with fast convergence speed and small overshoot than the BFC and the SORFC. The convergence speed of the BFC method is lower than other two control methods. For the control loop of chamber temperature with long delay time, the SORFC has a satisfied control performance with less overshoot and stable error than the BFC and PI control.