Clipping Effect on Growth and Plant Water Use Response to Diurnal Variation of Vapor Pressure Deficit in Cenchrus biflorus Roxb

Cenchrus biflorus called Karangiya in the Hausa language is an annual pastoral grass which is a valuable herbaceous fodder in dry land region in the context of climate change. However, little is known about the plant water use under the effects of cut in West Africa Sahel like Niger where the plant is a multipurpose grass species. Therefore, this study investigated the impact of grazing (simulated by shoot cuts) on biomass production. Cenchrus biflorus Roxb was grown on field plots and in pots and subjected to shoot cuts at different levels (3 cm and 5 cm from soil surface). The effect of shoot cuts on drought tolerance was evaluated by assessing the response of transpiration to the diurnal variation of vapor pressure deficit (VPD). Results showed that the biomass production varied in response to shoot cuts depending on the culture system, and the level or frequency of cuts. The mean biomass production increased significantly especially in field plots for 5 cm cuts compared to those at 3 cm and the control treatment. In addition, transpiration was highly increased in response to the VPD increase. Shoot cuts significantly reduced transpiration, whatever the level, largely because they reduced leaf surface. We concluded that moderate grazing (cuts to 5cm) can improve biomass production and allow better adaptation to water deficit as they significantly reduced water loss through transpiration. The study recommends the cropping of the Cenchrus biflorus as climate solution as it performs better under water deficit for improving grazing resilience in Niger.

Evaluation of the treatment effect of rear slope cutting on hydrodynamic pressure landslides:A case study

After the impoundment of the Three Gorges Reservoir,some huge ancient landslides were reactivated and deformed,showing typical hydrodynamic pressure landslide characteristics.The Baishuihe landslide was a typical hydrodynamic pressure landslide.The management department conducted slope cutting treatments from 2018 to 2019.To evaluate the treatment effect of rear slope cutting,this study analyzed the data of the surface deformation survey and field monitoring over the past 20 years and the characteristics of the reservoir water-triggered Baishuihe landslide deformation,and calculated the seepage field,displacement field,and stability coefficient before and after landslide treatment.The results showed that the deformation of the Baishuihe landslide was primarily related to a decrease in the reservoir water level.Owing to the poor permeability of the landslide soil,the decrease in the reservoir water level produced a seepage force pointing to the outside of the landslide body,leading to the step deformation of the landslide displacement.The landslide was treated by rear slope cutting,and the“step”deformation of the landslide disappeared after treatment.The hydrodynamic pressure caused by the change in reservoir water after cutting the slope did not disappear.However,as the slope cutting greatly reduced the overall sliding force of the landslide,its stability was greatly improved.Notably,high stability can still be ensured under extreme rainfall after treatment.Slope cutting is effective for treating hydrodynamic pressure landslides.This study can provide effective technical support for the treatment of reservoir landslides.

CNPC Making Efforts to Relieve Personnel Pressure

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Prospect of HDR geothermal energy exploitation in Yangbajing,Tibet,China,and experimental investigation of granite under high temperature and high pressure

Hot dry rock （HDR） geothermal energy, almost inexhaustible green energy, was first put forward in the 1970s. The development and testing of HDR geothermal energy are well reported in USA, Japan, UK, France and other countries or regions. In this paper, the geological characters of Yangbajing basin were first analyzed, including the continental dynamic environments to form HDR geothermal fields in Tibet, the tectonic characteristics of south slope of Nyainqentanglha and Dangxiong-Yangbajing basin, and the in-situ stresses based on the investigations conducted, and then the site-specific mining scheme of HDR geothermal resources was proposed. For the potential development of HDR geothermal energy, a series of experiments were conducted on large-scale granite samples, 200 mm in diameter and 400 mm in length, at high temperature and high triaxial pressure for cutting fragmentation and borehole stability. For the borehole stability test, a hole of 40 mm in diameter and 400 mm in length was aforehand drilled in the prepared intact granite sample. The results indicate that the cutting velocity obviously increases with temperature when bit pressure is over a certain value, while the unit rock-breaking energy consumption decreases and the rock-breaking efficiency increases with temperature at the triaxial pressure of 100 MPa. The critical temperature and pressure that can result in intensive damage to granite are 400-500℃ and 100-125 MPa, respectively.

What can the changes in shield resistance tell us during the period of shearer's cutting and neighboring shields' advance?

In order to determine the influence of shearer's cutting and neighboring shields' advance on the support resistance variation, leg pressure data of all 235 shields in the panel LW61 of Cumberland coal mine were analyzed. The results show that the relationship between the leg pressure increment and the distance from shield to front drum of shearer is a quadratic function and that the higher leg pressure increment before shield advance tends to be related to adverse roof conditions. In addition, the three proposed leg pressure increment-related parameters and the three traditional parameters(time-weighted average pressure, setting pressure, and final pressure) of approximately 32000 shield supporting cycles were calculated by a self-developed software package to analyze the correlation between them. The results show that there is a powerful connection between them, and that the three proposed leg pressure increment-related parameters could be used as the indexes to evaluate the interaction between shields and the roof, and to identify the periodic weighting.

The test research on partial relieving pressure for the entry in the deep mine under high stress and friable surrounding rock

Based on the geological condition of Zhangxiaolou deep mine in Xuzhou mining area, under 986 m in depth, 20.6-31.6 MPa in maximum horizontal principal stress, and friable and fractured surrounding rock, test researches on partial relieving pressure were completed for the entry with U-steel arched yielding support. The relieving pressure parameters, technology process and results of springing blasting by boreholes and excavating pockets in the two sides of entry were introduced. It is demonstrated that springing will not be shaped under the condition of single borehole arrangement after exploded, the arrangement by a group, it will make borehole bottom form springing in 0.6-0.8 m in diameter, that convergence of two sides and roof to floor have some increments by using springing blasting for reliving pressure. This kind of method for reliving pressure is not suitable to use in the deep mine, and that the convergence of two sides obviously declined by excavating pocket in two sides, it can be still used in the entry with metal support, while maintenance of entry in deep mines is difficult, and can not be supported by bolt or bolt with wire mesh.

Prediction of Cuttings-Induced Annular-Pressure Loss in Extended-Reach Wells

Drill cuttings are broken bits of solid material removed from a borehole drilled by rotary,percussion,or auger methods and brought to the surface in the drilling mud.When these cuttings enter the annulus,they have an effect on the drillingfluid rheology and density,which is,in general,quite difficult to evaluate.By introducing an empirical correlation for the rheological properties of cuttings-laden drillingfluids,this study proposes a pres-sure-loss prediction method for an extended-reach well(ERW).After verifying the accuracy of this method,a case study is considered and a sensitivity analysis is conducted assuming a yield-power lawfluid.The results show that an increased concentration of cuttings in the annulus contributes to an increased annular pressure loss.Com-pared to their effect on the drillingfluid density,cuttings have a greater impact on the drillingfluid rheology.A larger rate of penetration contributes to an increased annular pressure loss.For higher drillingfluidflow rates,the annular pressure lossfirst decreases and then it increases.In addition,the annular pressure loss becomes high-er as the cuttings’particle size decreases and the cuttings’concentration grows.

Comparative Analysis of the Distribution Characteristics of Floor Stress Field between Gob-Side Entry Retaining with Roof Cutting and Conventional Mining

All coal fields in North China are affected by floor confined water to varying degrees, floor failure and water inrush risk have always been a major problem to baffle coal mining activities. Roof cutting and pressure relief and the lack of protective coal pillar can cause the change of floor stress field, leading to the change of the floor failure depth, stress field of floor is the key to determine the depth of floor failure. In order to deeply study the distribution characteristics of floor stress field in gob-side entry retaining mining with roof cutting, taking the 50107 and 50109 working faces of Dongdong Coal Mine in Chenghe as the research objects, the numerical simulation software is used to simulate the floor stress field distribution of gob-side entry retaining mining with roof cutting and conventional mining. The distribution characteristics of the floor stress field of the working face are compared and analyzed under the three modes of conventional mining of reserved coal pillar, the first mining face of gob-side entry retaining with roof cutting and gob-side entry retaining with roof cutting. The results show that the peak stress concentration in front of the working face all occurs at 10 m under the three mining modes. The stress concentration area in front of conventional working face of reserved coal pillar is mainly in the middle of the working face. The stress concentration area in front of the first working face of gob-side entry retaining with roof cutting (50107) is located in the middle of the working face and the side of the working face of the retaining roadway. The stress concentration area of the working face (50109) is mainly in the middle and the two ends of the working face. The order of the peak value of the maximum concentrated stress in front of the working face is conventional working face of reserved coal pillar > the first working face of gob-side entry retaining with roof cutting (50107) > working face of gob-side entry retaining with roof cutting (50109). There is a stress reduction zone behind the working face, but there is a stress concentration phenomenon extending to the outside of the roadway, and the stress distribution is obviously different. Conventional working face of reserved coal pillar and the first working face of gob-side retaining with roof cutting (50107) show a double peak form of stress concentration on the outside of the two ends of the roadway, and the peak value of the concentrated stress at the rear of the working face is in the following order: On the side close to the transportation roadway, conventional working face of reserved coal pillar = the first working face of gob-side entry retaining with roof cutting (50107) > working face of gob-side entry retaining with roof cutting (50109);on the side close to the return airway, conventional working face of reserved coal pillar > the first working face of gob-side entry retaining with roof cutting (50107) > working face of gob-side entry retaining with roof cutting (50109).

斜切挑坎横向压力差研究

斜切挑坎在挑流设计中是一种常用的挑坎体型,能使水流在纵向上充分扩散,避免水流集中冲击于同一位置。斜切体型设计会使挑射水流在运动过程中在横向方向上呈现扩散角度增大的现象,但对此现象的深入研究较少。本文主要针对长边侧与短边侧之间的横向压力差进行研究,探究斜切挑坎横向压力差受挑坎尺寸与来流条件的影响,为后续斜切挑坎水舌横向扩散研究提供相关参考依据。本文使用数值模拟方法对不同挑坎尺寸与来流条件下斜切挑坎的出流情况进行模拟,分析了斜切挑坎内横向压力差的分布特征,以及挑坎尺寸与来流条件对横向压力差的影响。研究发现,最大横向压力差位于斜切挑坎短边边墙末端底板位置,横向压力差与斜切角度、来流流速、来流水深呈正相关,与挑坎半径呈负相关,并拟合了最大横向压力差与挑坎尺寸、来流条件有关的计算式。研究成果对斜切挑坎挑流水力设计具有一定的借鉴意义。

Cyclone dimensionless pressure drop,cut size,and separation slope:One dimensionless number(Reynolds)to rule them all

The flow field and performance characteristics of the high-efficiency Stairmand cyclone have been computationally investigated at a wide range of Reynolds numbers Reout=84−252876 by varying the cyclone diameter,inlet velocity,operating temperature and pressure using the LES simulations.The effects of these parameters on the dimensionless cyclone performance characteristics(Euler number,square root of Stokes number and slope of the transformed grade efficiency curve)and dimensionless lip flow and lip velocity have been revealed.Five critical Reynolds numbers which correspond to the transition between different regimes and sub-regimes have been determined.All three dimensionless cyclone performance characteristics and two lip flow characteristics are ruled by the Reynolds number.

动压巷道围岩变形机理及其控制技术研究

针对寺河煤矿二号井动压巷道在工作面回采过程中存在的围岩变形严重及工作面支架阻力过大等问题,采用现场监测与数值模拟相结合的手段,对动压巷道围岩变形机理及其控制技术进行了系统研究。结果表明,巷道在经受掘进支护及工作面的开采动压影响后,围岩应力水平升高,且两侧应力不平衡,帮部不对称变形严重,巷道围岩变形主要分为单侧采用影响与两侧采动影响2个阶段,巷道变形主要是因为采区大巷两侧工作面采动产生的应力扰动作用,导致巷道承载性能持续恶化,围岩发生反复变形破坏。据此,研究提出采用预裂切顶卸压技术对动压巷道变形实施有效控制,确定合理的切顶卸压高度与角度分别为16.5 m与60°。通过现场实践,对动压巷道实施切顶卸压后,围岩顶底板及两帮移近量较卸压前得到了有效控制,工作面支架阻力显著降低,保证了工作面动压巷道围岩的稳定。

切顶卸压沿空留巷技术在厚煤层综采工作面的应用

切顶卸压沿空留巷作为一种无煤柱开采工艺,在一定程度上可以提升煤炭资源的回收利用率、提升矿井生产的连续性、增加煤矿企业的经济效益。为解决工作面交替紧张及煤炭资源回采率低等问题,以山西西山煤电股份有限公司马兰矿18505综采工作面运输顺槽为研究对象,通过理论计算和工程实践相结合的研究方式,进行了切顶卸压沿空留巷工艺方案的设计及巷道围岩控制措施的相关研究,并提出采用“预裂爆破切顶+恒阻大变形锚索补强支护”的沿空留巷技术方案。根据现场实际监测效果可知,在留巷30天后,巷道围岩的变形基本趋于稳定,顶底板最大变形量为178.26 mm,巷道两帮的最大移近量为85.34 mm,完全符合沿空留巷的实际应用标准,保障了工作面的安全回采。

采煤工作面切顶卸压留巷技术研究

文章以3302回风巷留巷为工程背景,对切顶卸压留巷技术方案及应用效果进行分析。在3302回风巷留巷中,通过高强锚索进行超前支护,为后续留巷创造良好条件;通过定向预裂爆破切顶使得留巷段顶板与采空区顶板形成切顶线,达到采空区顶板沿切顶线垮落;通过顶板临时支护及挡矸支护,确保采空区垮落期间顶板稳定并避免采空区破碎矸石入侵留巷空间。工程应用后,3302回风巷留巷段顶板下沉量控制在251 mm以内,巷道断面可满足后续使用需要。

综采工作面无煤柱开采技术研究

针对亿欣煤业15号煤综采工作面采用传统采煤工艺留设煤柱造成资源浪费严重、煤炭回收率低、巷道掘进及返修工程量大等问题,以15号煤XV1213巷道为背景开展无煤柱开采技术研究,通过数值模拟分析了巷道顶板无切缝和有切缝模型的应力和位移情况,验证了顶板切缝对巷道围岩应力和变形的改善作用,并根据工作面现场条件设计了巷恒阻大变形锚索关键参数、顶板定向预裂切缝关键参数和无煤柱自成巷支护方案。现场应用表明,无煤柱成巷区巷道顶板整体下沉量较小,碎石巷帮无明显侧鼓现象,实体煤帮无明显片帮现象,满足留巷安全使用要求。经计算,切顶卸压无煤柱开采每米可创造经济效益8763.28元,经济效益显著。

综采工作面顶板切顶卸压沿空留巷围岩控制技术

为解决沿空掘巷存在大量煤柱损失、影响采掘接替等问题,同时防止回采过程中巷道产生严重变形,决定采用切顶卸压和综合支护方案对巷道围岩进行有效控制。针对2号煤层21206综采工作面复合顶板,采用理论分析和FLAC^(3D)数值模拟方法,确定了切顶卸压参数,其切顶角度为15°,切顶深度为9 m;将沿空巷道划分为超前支护区、滞后临时支护区和成巷稳定区,并采取不同的支护形式。综合支护方案实施,沿空留巷60 d内顶板下沉量最大值降低49.3%;两帮移近量最大值降低57.3%;工作面多回收煤炭15.6万t,并节省1条长度为1710 m的掘进巷道,并节省施工工期6个月,具有显著的经济效益。

薄煤层切顶留巷工作面采空区瓦斯治理技术

针对薄煤层切顶留巷工作面采空区瓦斯涌出量大的问题,提出在6303工作面通过控制采面配风、及时密闭挡矸支护漏风裂隙等措施有效减少采空区瓦斯涌出量,同时采用高位钻孔、低位钻孔及埋管方式抽采采空区瓦斯。现场应用后,采空区瓦斯抽采量稳定在4.5~7.2 m^(3)/min,采面内及回风流内瓦斯体积分数控制在0.28%以内,在后续回采期间未出现瓦斯涌出异常、体积分数突然增高等情况。现场采用的控制采空区漏风+采空区瓦斯抽采方式实现了薄煤层切顶留巷工作面采空区瓦斯有效治理。

巷旁静态胀裂切顶卸压技术应用研究

为解决煤矿井下沿空留巷巷道因受相邻工作面回采动压影响造成巷道矿压显现剧烈、围岩变形量大等问题,在现有沿空留巷切顶卸压技术基础上提出静态胀裂切顶卸压技术,用于切断沿空留巷巷道顶板与相邻工作面上覆岩层顶板联系,通过理论分析、计算及实验测定等方法,确定静态胀裂切顶卸压关键技术参数并制定具体技术方案,通过井下现场应用,结果表明,留巷巷道高度最大减小1.05 m,宽度最大减小0.65m,巷道围岩变形量最大显著减小,达到预期效果。

Dynamic failure of dry and fully saturated limestone samples based on incubation time concept

This paper outlines the results of experimental study of the dynamic rock failure based on the comparison of dry and saturated limestone samples obtained during the dynamic compression and split tests. The tests were performed using the Kolsky method and its modifications for dynamic splitting. The mechanical data(e.g. strength, time and energy characteristics) of this material at high strain rates are obtained. It is shown that these characteristics are sensitive to the strain rate. A unified interpretation of these rate effects, based on the structuraletemporal approach, is hereby presented. It is demonstrated that the temporal dependence of the dynamic compressive and split tensile strengths of dry and saturated limestone samples can be predicted by the incubation time criterion. Previously discovered possibilities to optimize(minimize) the energy input for the failure process is discussed in connection with industrial rock failure processes. It is shown that the optimal energy input value associated with critical load, which is required to initialize failure in the rock media, strongly depends on the incubation time and the impact duration. The optimal load shapes, which minimize the momentum for a single failure impact, are demonstrated. Through this investigation, a possible approach to reduce the specific energy required for rock cutting by means of high-frequency vibrations is also discussed.

Vegetable Oil-Based Nanolubricants in Machining:From Physicochemical Properties to Application

Cutting fluid is crucial in ensuring surface quality and machining accuracy during machining.However,traditional mineral oil-based cutting fluids no longer meet modern machining’s health and environmental protection require-ments.As a renewable,pollution-free alternative with excellent processing characteristics,vegetable oil has become an inevitable replacement.However,vegetable oil lacks oxidation stability,extreme pressure,and antiwear proper-ties,which are essential for machining requirements.The physicochemical characteristics of vegetable oils and the improved methods’application mechanism are not fully understood.This study aims to investigate the effects of viscosity,surface tension,and molecular structure of vegetable oil on cooling and lubricating properties.The mechanisms of autoxidation and high-temperature oxidation based on the molecular structure of vegetable oil are also discussed.The study further investigates the application mechanism and performance of chemical modification and antioxidant additives.The study shows that the propionic ester of methyl hydroxy-oleate obtained by epoxidation has an initial oxidation temperature of 175℃.The application mechanism and extreme pressure performance of conventional extreme pressure additives and nanoparticle additives were also investigated to solve the problem of insufficient oxidation resistance and extreme pressure performance of nanobiological lubricants.Finally,the study discusses the future prospects of vegetable oil for chemical modification and nanoparticle addition.The study provides theoretical guidance and technical support for the industrial application and scientific research of vegetable oil in the field of lubrication and cooling.It is expected to promote sustainable development in the manufacturing industry.

PROTOS 70卷接机组卷烟纸补偿差动齿轮箱的改进

PROTOS 70卷接机组卷烟纸补偿差动齿轮箱存在渗漏油问题,通过对卷烟纸补偿传动机构的工作原理及故障原因进行分析,提出了改进措施:在箱体上加装泄压装置和呼吸器,可将箱体内的油气释放出来,从而达到延缓箱体泄漏的目的。