Application of high-pressure water jet technology and the theory of rock burst control in roadway

This paper puts forward using high-pressure water jet technology to control rock burst in roadway, and analyzes the theory of controlling rock burst in roadway by the weak structure zone model. The weak structure zone is formed by using high-pressure water jet to cut the coal wall in a continuous and rotational way. In order to study the influence law of weak structure zone in surrounding rock, this paper numerically analyzed the influence law of weak structure zone, and the disturbance law of coal wall and floor under dynamic and static combined load. The results show that when the distance between high-pressure water jet drillings is 3 m and the diameter of drilling is 300 mm, continuous stress superposition zone can be formed. The weak structure zone can transfer and reduce the concentrated static load in surrounding rock, and then form distressed zone. The longer the high-pressure water jet drilling is, the larger the distressed zone is. The stress change and displacement change of non-distressed zone in coal wall and floor are significantly greater than that of distressed zone under dynamic and static combined load. And it shows that the distressed zone can effectively control rock burst in roadway under dynamic and static combined load. High-pressure water jet technology was applied in the haulage gate of 250203 working face in Yanbei Coal Mine, and had gained good effect. The study conclusions provide theoretical foundation and a new guidance for controlling rock burst in roadway.

In situ experimental study on TBM excavation with high-pressure water-jet-assisted rock breaking

China’s first high-pressure hydraulically coupled rock-breaking tunnel boring machine(TBM) was designed to overcome the rock breaking problems of TBM in super-hard rock geology, where high-pressure water jet system is configured, including high-flow pump sets, high-pressure rotary joint and high-pressure water jet injection device. In order to investigate the rock breaking performance of high-pressure water-jet-assisted TBM, in situ excavation tests were carried out at the Wan’anxi Water Diversion Project in Longyan, Fujian Province, China, under different water jet pressure and rotational speed. The rock-breaking performance of TBM was analyzed including penetration, cutterhead load, advance rate and field penetration index. The test results show that the adoption of high-pressure water-jet-assisted rock breaking technology can improve the boreability of rock mass, where the TBM penetration increases by 64% under the water jet pressure of 270 MPa. In addition, with the increase of the water jet pressure, the TBM penetration increases and the field penetration index decreases. The auxiliary rock-breaking effect of high-pressure water jet decreases with the increase of cutterhead rotational speed. In the case of the in situ tunneling test parameters of this study, the advance rate is the maximum when the pressure of the high-pressure water jet is 270 MPa and the cutterhead rotational speed is 6 r/min. The technical superiority of high-pressure water-jet-assisted rock breaking technology is highlighted and it provides guidance for the excavation parameter selection of high-pressure hydraulically coupled rock-breaking TBM.

Dynamic effects of high-pressure pulsed water jet in low-permeability coal seams

Mine gas extraction in China is difficult due to the characteristics such as micro-porosity,low-permeability and high adsorption of coal seams.The pulsed mechanismof a high-pressure pulsed water jet was studied through theoretical analysis,experimentand field measurement.The results show that high-pressure pulsed water jet has threedynamic properties.What's more,the three dynamic effects can be found in low-permeabilitycoal seams.A new pulsed water jet with 200-1 000 Hz oscillation frequency andpeak pressure 2.5 times than average pressure was introduced.During bubble collapsing,sound vibration and instantaneous high pressures over 100 MPa enhanced the cuttingability of the high-pressure jet.Through high-pressure pulsed water jet drilling and slotting,the exposure area of coal bodies was greatly enlarged and pressure of the coal seamsrapidly decreased.Therefore,the permeability of coal seams was improved and gas absorptionrate also decreased.Application results show that gas adsorption rate decreasedby 30%-40%and the penetrability coefficient increased 100 times.This proves that high-pressurepulsed water is more efficient than other conventional methods.

Modeling on impact zone volume generated by coherent supersonic jet and conventional supersonic jet

The supersonic oxygen supply technology, including the coherent supersonic jet and the conventional supersonic jet, is now widely adopted in electric arc furnace steelmaking process to increase the bath stirring, reaction rates and energy efficiency. However, there has been limited study on the impact characteristics of the coherent supersonic jet and the conventional supersonic jet. Thus, integrating theoretical models and numerical simulations, an optimized theoretical model was developed to calculate the volume of the impact zone generated by coherent and conventional supersonic jets. The optimized theoretical model was validated by water model experiments. The results show that the jet impact zone volume with coherent supersonic jet is much larger than that with conventional supersonic jet at the same lance height. The kd value, a newly defined variable that is the product of the dimensionless quantity of velocity and free distance, reflects the velocity attenuation and the potential core length of the main supersonic jet, which is a key parameter of the optimized theoretical model. The optimized theoretical model can well predict the jet impact zone volumes of coherent and conventional supersonic jets with the error no more than 3.62 and 9.37%, respectively.

三股对撞式撞击流反应器微观混合性能研究

采用高速数码相机对三股对撞式撞击流反应器不同入口雷诺数下的流场特征进行了研究,并采用碘化物-碘酸盐平行竞争反应体系,考察了不同喷嘴直径下的入口雷诺数、不同溶液体积流量比对离集指数的影响。结果表明:入口雷诺数、溶液体积流量比对离集指数有明显的影响。增大入口雷诺数,三股流体高速撞击破碎成的液滴粒径逐渐减小,液滴雾化程度增加,离集指数减小,微观混合效果增加;增大体积流量比,溶液局部浓度增大,导致混合不均匀,离集指数增大。与传统撞击流反应器相比,三股对撞式撞击流反应器离集指数为传统撞击流反应器的2/5,表现出了较好的微观混合性能,更适用于不等溶液体积流量比的液液快速混合反应。

新型太阳能喷射与电压缩式联合制冷系统的研究

提出一种新型的太阳能喷射与电压缩联合制冷系统,其既可以利用太阳能喷射式制冷又可以利用电能驱动压缩式制冷,可提高太阳能与辅助能源的综合利用率。对该系统中以R141b作为制冷工质,采用斜盘式压缩机的辅助电压缩制冷系统进行了理论循环计算与实验研究。实验表明,该辅助电压缩制冷系统的性能系数达到2.53。与传统的辅助能源应用方式相比,该辅助电压缩式制冷系统能更高效地利用常规能源,提高新型太阳能喷射制冷系统的综合节能效果。

常规雷达JEM特征分析与目标分类的研究

该文研究了常规雷达回波中喷气发动机调制(JEM)特征产生机理、提取方法及用于目标分类的效能,先从理论上分析了常规雷达飞机回波中JEM特征的产生机理,并比较了直升机、螺旋桨飞机和涡扇喷气机回波中JEM周期特征的差别。再讨论了实际回波中时域、频域、时频域方法分析和提取JEM周期特征的优劣,最后用AR双谱切片技术提取的JEM周期特征进行了目标分类和辨识实验,结果表明;JEM周期特征用于常规防空雷达飞机的分类是有效的,但又是有限的。

脉冲爆震发动机新型点火系统的优化设计

为了缩短爆燃向爆震转捩的时间和距离,该文将一种新型点火系统——火焰喷射点火系统应用于脉冲爆震发动机。利用二维数值模拟研究不同喷射点火系统结构参数(前端圆柱段长度,直径以及末端喷嘴的直径)下爆燃向爆震转捩的时间和距离,并将研究结果与传统点火系统的爆燃向爆震转捩转变时间进行对比。结果发现:对于该文所采用的PDE模型,最有效的副室结构为喷嘴直径4 mm,副室长度10 mm,体积3.8 cm3。此外还发现喷射点火系统比传统点火系统能更有效地缩短爆燃向爆震转捩的时间和距离,其效率约为后者的1.26倍。

高频喷射通气对犬循环功能的影响

目的 :研究麻醉犬高频喷射通气 (HFJV) (10 0次 /min ,驱动压 0 .5kg/cm2 )和常频机械通气 (CMV) (2 0次 /min ,驱动压力 0 .5kg/cm2 )对循环功能的影响。方法 :用Kubicek理论测定HFJV对循环功能的影响。结果 :HFJV能提高动脉血氧分压 (P <0 .0 5 ) ,降低二氧化碳分压 (P <0 .0 5 )。HFJV和CMV可使每搏输出量显著降低 (P <0 .0 5 ) ,但每分心输出量无显著改变 (P >0 .0 5 )。停止常频机械通气后 ,每搏输出量仍显著降低 (P <0 .0 5 )。结论 :HFJV能提高动脉血氧分压 。

不同频率时高频喷射通气膈神经电位的影响

目的 :研究麻醉犬高频喷射通气 (15 0次 min、30 0次 min和 6 0 0次 min ,驱动压 0 .5kg cm2 )和常频机械通气 (16次 min ,驱动压 0 .5kg cm2 )对膈神经动作电位的频率、幅度和持续时间的影响。方法 :用电生理方法测定高频喷射通气时膈神经电位的变化。结果 :常频机械通气和高频喷射通气 (15 0次 min和 30 0次 min)后 ,膈神经动作电位的幅度无显著改变 (P >0 .0 5 )。高频喷射通气 (6 0 0次 min) 15min ,膈神经动作电位幅度显著增大 (P <0 .0 5 )。通气 5和 15min ,膈神经动作电位的放电频率显著降低 (P <0 .0 1)。停止常频机械通气 15min ,膈神经动作电位的持续时间显著缩短 (P <0 .0 5 )。结论 :中等频率的高频喷射通气比高频率的高频喷射通气的效果好。

三峡三期土石围堰防渗墙施工工艺

根据三峡三期土石围堰防渗体设计要求和施工特点,选择了振孔高喷、常规钻孔高喷、钻喷一体化高喷和自凝灰浆等4种防渗墙施工工艺进行论证。在分析比较各种施工工艺特性的基础上,对4种工艺进行了现场试验,试验结果表明:4种工艺均可用于三峡三期土石围堰防渗墙施工,并确定上游围堰采用"自凝灰浆+常规钻孔高喷+钻喷一体化高喷",下游围堰采用"振孔高喷为主,辅以常规钻孔高喷"的施工方案。在施工中,各种施工工艺相互配合,发挥了各自的优势,确保了三峡三期土石围堰防渗墙工程按期、高质量地完成。

不同通气方式对实验性Ⅱ型呼吸衰竭犬通气效果的比较

目的：评价不同通气方式的通气效果并探讨通气作用原理．方法：通过蒸汽吸入致伤，复制了９只犬Ⅱ型呼吸衰竭模型．结果：①当限定ＣＭＶ峰值气道压≤１２ｃｍＨ２Ｏ时，有ＣＯ２潴留，不能满足通气要求；②ＨＦＪＶ＋ＰＥＥＰ与单纯ＨＦＪＶ相比较，Ｖｃｏ２（２．９１±１．０９对４．９０±０．６５ｍｌ／（ｍｉｎ·ｋｇ）显著减少（Ｐ＜０．０１），Ｐａｃｏ２（１０．２８±１．３６对７．０５±１．３７ｋＰａ）大幅度增加（Ｐ＜０．０１），Ｐａｏ２（７．２３±２．２７对９．３３±２．１８ｋＰａ）显著降低（Ｐ＜０．０１），可能与ＶＴ和ＶＡ的减少有关；③ＨＦＴＪＶ与ＨＦＪＶ相比较，Ｖｃｏ２（６．３２±１．３０ｍｌ／（ｍｉｎ·ｋｇ）增加，Ｐａｃｏ２（５．９９±０．９０ｋＰａ）减少均达到非常显著水平（Ｐ＜０．０１），Ｐａｏ２维持稳定．结论：ＨＦＴＪＶ确有增强ＣＯ２的排除效能，其作用应归因于解剖和生理死腔量的减少，其可能成为解决Ⅱ型呼吸衰竭ＣＯ２排除障碍的有效途径．

In-situ remediation of deep petroleum-contaminated soil injection

A computational fluid dynamics(CFD)numerical simulation and field experiment were used to investigate optimal operating parameters of high-pressure jet grouting equipment and clarify the boundary law of the injection area in the remediation process.The response surface optimization design results show that the optimal injection pressure is 30 MPa,rotation speed is 23 r/min,commission speed is 30 cm/min,and the optimal injection diameter is 147.3 cm.Based on the CFD numerical simulation,the ratio of the injection core,turbulent zone,and seepage zone is approximately 1∶4∶2.The distribution law of jet core,turbulence zone and seepage zone at different cross-sections under 30 MPa operating conditions is as follows:The jet core radius is approximately 100 mm,the turbulence zone is mainly distributed at 100 to 500 mm,the seepage zone is mainly distributed at 500 to 700 mm,the seepage zone could be completed within 2 h,and the proportion of the three boundary zones in the injection zone is similar to that of the numerical simulation.This study provides theoretical parameters and practical reference for the remediation of deep pollution via in-situ chemical oxidation in the Loess Plateau soil environment.

渤海油田水平井冲砂技术的应用及评述

本文介绍了渤海油田水平井冲砂技术(常规冲砂技术、氮气泡沫清砂技术、文丘里冲捞砂技术)的原理及特点。对渤海油田水平井冲砂进行了总结,对其他油田的冲砂有很好的借鉴作用。

Discussion on Anti-Seepage Technologies in the Construction of Small-Scale Rural Water Conservancy Projects

In order to ensure the sustainable growth of rural economy,it is necessary to carry out further research on small-scale water conservancy projects and solve the seepage issue in rural areas.Based on the application significance of small-scale rural water conservancy projects and the analysis of anti-seepage technologies,along with specific examples,this paper specifically discusses the application of high-pressure jet technology,so as to provide reference for the development of engineering construction.

AP1000核电站常规岛高能管道断裂分析

AP1000核电站常规岛设计必须考虑高能管道断裂的影响。利用应力分析方法和特定位置法对管道断裂位置判定进行了分析;采用流体力学的方法对主蒸汽和主给水管道断裂荷载进行了计算;利用经验公式,结合管道断裂后的几何特性,对AP1000核电站常规岛主蒸汽管道断裂后端部不受约束和端部受约束两种情况下的主要喷射几何尺寸进行了计算。通过计算,得出了主蒸汽管道断裂后的荷载和主要喷射几何特性。通过计算分析得出结论,常规岛高能管道断裂后荷载和喷射影响范围很大,可以作为高能管道断裂防护设计的依据。