Theory and application of rock burst prevention using deep hole high pressure hydraulic fracturing

In order to analyze the mechanism of deep hole high pressure hydraulic fracturing, nonlinear dynamic theory, damage mechanics, elastic-plastic mechanics are used, and the law of crack propagation and stress transfer under two deep hole hydraulic fracturing in tectonic stress areas is studied using seepage-stress coupling models with RFPA simulation software. In addition, the effects of rock burst control are tested using multiple methods, either in the stress field or in the energy field. The research findings show that with two deep holes hydraulic fracturing in tectonic stress areas, the direction of the main crack propagation under shear-tensile stress is parallel to the greatest principal stress direction. High-pressure hydraulic fracturing water seepage can result in the destruction of the coal structure, while also weakening the physical and mechanical properties of coal and rock. Therefore the impact of high stress concentration in hazardous areas will level off, which has an effect on rock burst prevention and control in the region.

Elimination of Fuel Pressure Fluctuation and Multi-injection Fuel Mass Deviation of High Pressure Common-rail Fuel Injection System

The influence of fuel pressure fluctuation on multi-injection fuel mass deviation has been studied a lot,but the fuel pressure fluctuation at injector inlet is still not eliminated efficiently.In this paper,a new type of hydraulic filter consisting of a damping hole and a chamber is developed for elimination of fuel pressure fluctuation and multi-injection fuel mass deviation.Linear model of the improved high pressure common-rail system（HPCRS）including injector,the pipe connecting common-rail with injector and the hydraulic filter is built.Fuel pressure fluctuation at injector inlet,on which frequency domain analysis is conducted through fast Fourier transformation,is acquired at different target pressure and different damping hole diameter experimentally.The linear model is validated and can predict the natural frequencies of the system.Influence of damping hole diameter on fuel pressure fluctuation is analyzed qualitatively based on the linear model,and it can be inferred that an optimal diameter of the damping hole for elimination of fuel pressure fluctuation exists.Fuel pressure fluctuation and fuel mass deviation under different damping hole diameters are measured experimentally,and it is testified that the amplitude of both fuel pressure fluctuation and fuel mass deviation decreases first and then increases with the increasing of damping hole diameter.The amplitude of main injection fuel mass deviation can be reduced by 73%at most under pilot-main injection mode,and the amplitude of post injection fuel mass deviation can be reduced by 92%at most under main-post injection mode.Fuel mass of a single injection increases with the increasing of the damping hole diameter.The hydraulic filter proposed by this research can be potentially used to eliminate fuel pressure fluctuation at injector inlet and improve the stability of HPCRS fuel injection.

Stress characteristics of surrounding rocks for inner water exosmosis in high-pressure hydraulic tunnels

Seepage and stress redistribution are the main factors affecting the stability of surrounding rock in high-pressure hydraulic tunnels.In this work,the effects of the seepage field were firstly simplified as a seepage factor acting on the stress field,and the equilibrium equation of high pressure inner water exosmosis was established based on physical theory.Then,the plane strain theory was used to solve the problem of elasticity,and the analytic expression of surrounding rock stress was obtained.On the basis of criterion of Norway,the influences of seepage,pore water pressure and buried depth on the characteristics of the stress distribution of surrounding rocks were studied.The analyses show that the first water-filling plays a decisive role in the stability of the surrounding rock; the influence of seepage on the stress field around the tunnel is the greatest,and the change of the seepage factor is approximately consistent with the logarithm divergence.With the effects of the rock pore water pressure,the circumferential stress shows the exchange between large and small,but the radial stress does not.Increasing the buried depth can enhance the arching effect of the surrounding rock,thus improving the stability.

Safety estimation of high-pressure hydraulic cylinder using FSI method

Hydraulic cylinder is a primary component of the hydraulic valve systems.The numerical study of hydraulic cylinder to evaluate the stress analysis,the life assessment and the performance of operation characteristics in hydraulic cylinder were described.The calculation of safety factor,fatigue life,piston chamber pressure,rod chamber pressure and the change of velocity of piston with flow time after the beginning of hydraulic cylinder were incorporated.Numerical analysis was performed using the commercial CFD code,ANSYS with unsteady,dynamic mesh model,two-way FSI(fluid-structure interaction)method and k-εturbulent model.The internal pressure in hydraulic cylinder through stress analysis show higher than those of the yield strength.

Characteristics,origin and controlling effects on hydrocarbon accumulation of overpressure in foreland thrust belt of southern margin of Junggar Basin,NW China

Aiming at the differential distribution of overpressure in vertical and lateral directions in the foreland thrust belt in the southern margin of Junggar Basin,the study on overpressure origin identification and overpressure evolution simulation is carried out.Based on the measured formation pressure,drilling fluid density and well logging data,overpressure origin identification and overpressure evolution simulation techniques are used to analyze the vertical and lateral distribution patterns of overpressure,genetic mechanisms of overpressure in different structural belts and causes of the differential distribution of overpressure,and the controlling effects of overpressure development and evolution on the formation and distribution of oil and gas reservoirs.The research shows that overpressure occurs in multiple formations vertically in the southern Junggar foreland thrust belt,the deeper the formation,the bigger the scale of the overpressure is.Laterally,overpressure is least developed in the mountain front belt,most developed in the fold anticline belt,and relatively developed in the slope belt.The differential distribution of overpressure is mainly controlled by the differences in disequilibrium compaction and tectonic compression strengths of different belts.The vertical overpressure transmission caused by faults connecting the deep overpressured system has an important contribution to the further increase of the overpressure strength in this area.The controlling effect of overpressure development and evolution on hydrocarbon accumulation and distribution shows in the following aspects:When the strong overpressure was formed before reservoir becoming tight overpressure maintains the physical properties of deep reservoirs to some extent,expanding the exploration depth of deep reservoirs;reservoirs below the overpressured mudstone cap rocks of the Paleogene Anjihaihe Formation and Lower Cretaceous Tugulu Group are main sites for oil and gas accumulation;under the background of overall overpressure,both overpressure strength too high or too low are not conducive to hydrocarbon enrichment and preservation,and the pressure coefficient between 1.6 and 2.1 is the best.

Modeling and control for hydraulic transmission of unmanned ground vehicle

Variable pump driving variable motor(VPDVM) is the future development trend of the hydraulic transmission of an unmanned ground vehicle(UGV).VPDVM is a dual-input single-output nonlinear system with coupling,which is difficult to control.High pressure automatic variables bang-bang(HABB) was proposed to achieve the desired motor speed.First,the VPDVM nonlinear mathematic model was introduced,then linearized by feedback linearization theory,and the zero-dynamic stability was proved.The HABB control algorithm was proposed for VPDVM,in which the variable motor was controlled by high pressure automatic variables(HA) and the variable pump was controlled by bang-bang.Finally,simulation of VPDVM controlled by HABB was developed.Simulation results demonstrate the HABB can implement the desired motor speed rapidly and has strong robustness against the variations of desired motor speed,load and pump speed.

Advanced high-pressure plasma diagnostics with hairpin resonator probe surrounded by film and sheath

The hairpin probe using microwave resonance in plasma is applicable to high pressure 1.33 ×10^3-1.01×10^5 Pa）） as developed recently. In this work, an analytic model of the hairpin resonator probe surrounded by a thin dielectric layer and a sheath layer is proposed. The correction factor due to these surroundings is analytically found and confirmed by electromagnetic field finite difference time domain simulation, thus enabling the accurate measurement of electron density in a high-pressure non-equilibrium uniform discharge.

Comparison of Three Methods for Determination of Root Hydraulic Conductivity of Maize(Zea mays L.)Root System

Three techniques of root pressure probe, pressure chamber and high pressure flow meter were used to measure the hydraulic conductivities （Lpr） of whole root systems of young maize （Zea mays L.） seedlings grown hydroponically under either drought or normal water conditions. Compared to normal water conditions, drought stress simulated by polyethylene glycol 6 000 （osmotic potential =-0.2 MPa） reduced Lpr in the root system by over 50%. It indicated that water permeability in the roots decreased significantly when plants suffered from water shortages. Moreover, there was no significant difference （P〈 0.05） on the Lpr values in the root systems developed under a given water stress regime among the three techniques used. Therefore, all three methods are acceptable to study the hydraulic conductivity of maize seedling root systems. We have also highlighted some of the technical limitations of each method. It can be inferred that the root pressure probe is preferable for young maize seedlings because it is subtle and has the additional ability to determine solute transport properties, but the method is time consuming. Other advantages and disadvantages of each technique are discussed in order to acquaint researchers with basic information that could contribute to their choice of an appropriate technique for future studies.

Strength and energy exchange of deep sandstone under high hydraulic conditions

To investigate the influence of confining pressure and pore water pressure on strength characteristics,energy storage state and energy release intensity at peak failure of deep sandstone,a series of triaxial compression tests under hydraulic coupling conditions are carried out.By analyzing the process of rock deformation and failure,the stress thresholds of the rock are obtained.The change trend of total energy density,elastic energy density and dissipated energy density of deep sandstone in the pre-peak stage is obtained by the graphical integration method.By comparing the dynamic energy storage level of rocks under different confining pressures,the influence of pore water pressure on the energy dissipation at stress thresholds of crack closure stress,crack initiation stress,crack damage stress and peak stress is analyzed.Based on the ratio of pre-peak total energy density to post-peak total energy density,the interaction mechanism of confining pressure and pore water pressure for the rock burst proneness of deep sandstone is studied.The experimental results show that the peak stress of sandstone increases with the increase of confining pressure,while the existence of pore water pressure can weaken the peak stress of sandstone.In the stress stage from crack closure stress to peak stress,the dynamic energy storage level of rock presents a trend of the inverse“check mark”.Meanwhile,the larger the confining pressure,the higher the energy storage level of rock.However,the pore water pressure increases the degree of energy dissipation of rock and reduces the energy storage capacity of rock,and the degree of dissipation is linear with pore water pressure.The increase of confining pressure aggravates the instability and failure of deep sandstone,while pore water pressure has the opposite effect.The research results will provide necessary data support for the stability analysis of rock mass excavation in sandstone stratum under high stress and high pore water pressure.

Research on hydraulic slotting technology controlling coal-gas outbursts

Measured to control serious coal-gas outburst in coal seam were analyzed by theory and experimented in test site.A new technique to distress the coal-bed and drain methane,called hydraulic slotting,was described in detail,and the mechanism of hydrau- lic slotting was put forward and analyzed.The characteristic parameter of hydraulic slotting was given in Jiaozuo mining area and the characteristic of validity,adaptability and secu- rity was evaluated.The results show that the stress surrounding the strata and the gas in coal seam is released efficiently and thoroughly while new techniques are taken,as slot- ting at heading face by high pressure large diameter jet.The resistance to coal and gas outbursts is increased dramatically once the area of slotting is increased to a certain size. In the process of driving 2 000 m tunnel by hydraulic slotting excavation,coal and gas outburst never occurre.The technique could be used to prevent and control potential coal-gas outburst in the proceeding of tunnel driving,and the speed tunneling could be as high as more than 2 times.

Responses of Root Hydraulic Properties and Transpirational Factors to a Top Soil Drying in <i>Cajanus cajan</i>and <i>Sesbania sesban</i>

Responses of leaf area (LA), stomatal conductance (gs), root length (RL) and root hydraulic conductance per unit of root length (Lpunit) to top soil dryness were investigated. Pigeon pea (Cajanus cajan) and sesbania (Sesbania sesban) were grown in a vertical split-root system. From sixty-six days after sowing, the top soil was dried while the bottom soil was kept wet. Pigeon pea increased LA while maintaining leaf water potential (ΨL) by reducing gs. Increased transpirational demand through canopy development was compensated for by increasing water extraction in the bottom soil. This was achieved by increasing not only RL but also Lpunit. Sesbania kept constant levels of gs, causing a transient reduction of ΨL. ΨL of sesbania was, then, recovered by increasing only RL, but not Lpunit, in the bottom soil while suspending LA extension, suggesting that sesbania regulated only the root area to LA ratio. This study demonstrated a species-specific significance of Lpunit and coordination among Lpunit, RL, gs and LA in exploitation of wet-deeper soils in response to top soil dryness.

基于双重介质渗流-应力耦合模型的高压压水试验渗透参数反演

高压压水试验过程中岩体易发生水力劈裂产生裂隙,岩体内部孔隙、裂隙双重导水,渗流场和应力场相互作用,导致岩体渗透参数的时空变异性。基于高压压水试验反演渗透参数需考虑双重介质渗流-应力耦合作用下产生裂隙前后渗透系数的变化规律,利用渗流-应力耦合数值模型结合工程现场高压压水试验数据进行参数反演,计算得到不同压力阶段下灰岩岩体渗透率。主要结论如下:发生水力劈裂前,随着注液压力的增大,渗透率及孔隙水压力在不同压力阶段之间分界明显,渗透率反演值与规程公式计算值相近;发生水力劈裂后,岩体渗透率增大约2倍,孔隙介质渗透率和通过的流量出现陡减现象。

高压煤油恒速液动机转子倾覆现象的理论研究

介绍了高压煤油恒速液动机(简称“液动机”)的转子倾覆现象,分析了机理,并按照发生的原因将倾覆现象分为主动倾覆和被动倾覆。重点研究了主动倾覆,基于对转子柱塞组件的受力分析,提出了倾覆条件的数学表达,引入了无量纲的倾覆安全系数,以定量表达倾覆风险。分析了被动倾覆的原因,并提出了解决被动倾覆的方法。在产品设计中应避免出现主动倾覆和被动倾覆。

低透气性煤层高压脉冲射流割缝-压裂增透技术应用研究

针对盘州平关镇大坪煤矿18采区20号煤层复杂地质条件及瓦斯抽采难题,提出一种高压脉冲射流割缝导向压裂增透技术。为验证该技术效果,分析了其增透技术机理,并设计了4种试验方案进行对比分析。结果表明,采用高压脉冲射流割缝导向压裂方案在瓦斯抽采效果方面显著优于其他方法,与普通抽采、高压脉冲射流割缝、高压水力压裂抽采瓦斯相比,其平均每日抽采瓦斯浓度分别提高了3.01倍、1.41倍和1.67倍;平均每日抽采瓦斯纯流量也相应提升了2.86倍、1.42倍和1.62倍。经过90 d的抽采,该方案的抽采影响半径达到了5.06 m,分别为普通抽采、高压脉冲射流割缝和高压水力压裂抽采方案的2.56倍、1.25倍和1.29倍;在抽采效果相同的条件下,钻孔施工时间分别比普通抽采、高压脉冲射流割缝和高压水力压裂方案缩短了60%、32%和20%,瓦斯抽采达标所需时间分别比普通抽采、高压脉冲射流割缝和高压水力压裂方案缩短了70%、50%和62%。高压脉冲射流割缝导向压裂技术对低透气性煤层瓦斯治理效果较为理想,可供类似矿井借鉴。

6000t自由锻造水压机改油压机关键技术研究

本文提出了6000t自由锻造水压机升级改造的必要性,介绍了6000t自由锻造水压机升级改造的路径及改造后主要参数,阐述了控制系统升级改造方案及其关键技术。

超深埋隧洞防渗排水措施与衬砌外水压力分布规律

高外水压力是制约超深埋水工隧洞建设的关键性难题之一,以排水孔为中心的综合堵排措施是降低外水压力的主要举措。为克服传统排水孔实体单元法整体网格划分难度大和计算效率较低的问题,首先,基于ABAQUS平台开发了两节点排水孔线单元模型,并验证其在隧洞工程数值模拟分析中的正确性和有效性;其次,建立了考虑防渗排水措施的围岩-衬砌三维有限元模型,研究多种防渗排水措施下的隧洞渗流场及衬砌外水压力分布规律;最后,探讨了防渗灌浆圈与排水孔设计参数对外水压力分布的影响,提出了防渗灌浆圈与排水孔间隔布置的原则。研究结果表明:所开发的两节点排水孔线单元具有较高的精度,在排水孔数目繁多的模型中具有极高效率;排水孔数目越多、深度越大、排距越小,衬砌外水压力越低;排水孔能够有效降低衬砌的外水压力,而防渗灌浆圈降外压能力有限;在排水孔末端间隔一定厚度围岩后再施作防渗灌浆圈,可更有效发挥两者的降压作用。

柔性钻具水力导向射流喷嘴流场分析

现有柔性钻具钻井技术和水力喷射径向钻井技术在控制钻进方向上存在困难或有局限性。为实现钻井导向可控,设计了一种能够水力导向的高压射流喷嘴结构。建立导向喷嘴流体数值模型,利用数值模拟的方法进行流场分析,研究喷嘴倾角、喷嘴直径、喷嘴开启个数等参数对导向力、射流速度的定量关系,给出了导向力方向确定方法。结果表明:随着关闭喷嘴个数的增加,喷嘴导向力呈指数逐渐增大;轴向倾角越大,喷嘴导向力和最大喷射速度越大;喷嘴内径减小时,导向力和喷射速度都显著增大。通过数值模拟验证了射流喷嘴水力导向的可行性,分析结果和导向力的拟合公式对水力导向喷嘴钻进方向的研究具有指导意义。

Deformation defects and electron irradiation effect in nanostructured Al-Mg alloy processed by severe plastic deformation

In order to explore the exact nature of deformation defects previously observed in nanostructured Al-Mg alloys subjected to severe plastic deformation, a more thorough examination of the radiation effect on the formation of the planar defects in the high pressure torsion （HPT） alloys was conducted using high-resolution transmission electron microscopy （HRTEM）. The results show that high density defects in the HRTEM images disappear completely when these images are exposed under the electron beam for some duration of time. At the same time, lattice defects are never observed within no-defect areas even when the beam-exposure increases to the degree that holes appear in the areas. Therefore, it is confirmed that the planar defects observed in the HPT alloys mainly result from the significant plastic deformation and are not due to the radiation effect during HRTEM observation.

高瓦斯中硬煤层超高压水力割缝卸压增透技术及应用

为了提高高瓦斯中硬煤层卸压增透及瓦斯抽采效果,研究了顺层长钻孔超高压水力割缝技术,分析了其卸压增透机理,开展了超高压水力割缝现场试验,确定了等效割缝半径和有效瓦斯抽采半径,考察了超高压水力割缝技术的应用效果。研究结果表明:超高压水力割缝技术具有切割速度快、切割半径大等特点,相当于在钻孔周围煤体开采极薄保护层,平均单刀割缝时间9 min,单刀出煤量0.32~0.42 t,等效割缝半径为1.55~1.78 m;超高压水力割缝组单孔平均抽采浓度76.5%,单孔平均抽采纯量为0.089 m^(3)/min,分别是普通钻孔的4.58倍和4.05倍,是水力冲孔的1.2倍和1.43倍,可见该技术可以大幅度提高卸压增透及瓦斯抽采效果。

高内水压作用下围岩-叠合式衬砌承载机理力学分析

为探究圆形水工隧洞衬砌结构中围岩-叠合式衬砌联合承载的力学机理,针对珠江三角洲水资源配置工程“外衬管片-自密实混凝土填充层(SCC)-内衬钢管”三层叠合的衬砌结构形式,采用平面弹性复变函数理论的幂级数解法,从应力函数层面着手,基于围岩-衬砌相互作用关系以及应力边界条件建立了相应的力学模型,推导求解了在开挖荷载和内水压共同作用下围岩和各层衬砌域内任意点的应力分量,揭示了叠合式衬砌结构承载时的荷载传递机理和规律。然后通过边界应力结果以及与数值结果的比对,验证了提出方法的正确性;最后通过参数分析,着重讨论了高内水压对输水隧洞围岩和三层衬砌径向正应力和环向正应力的影响。结果表明:围岩-衬砌联合承载时,围岩和三层衬砌的径向正应力和环向正应力结果均符合余弦分布,而剪应力符合正弦分布;随着输水隧洞内水压增加,三层衬砌和围岩在径向上更趋于压缩,而环向正应力趋向于拉应力并增大。研究成果可为该类型衬砌防护工程的设计和施工提供理论依据。