AHFO-based soil water content sensing technology considering soil-sensor thermal contact resistance

The actively heated fiber-optic(AHFO)technology has become emerged as a research focus due to its advantages of distributed,real-time measurement and good durability.These attributes have led to the gradual application of AHFO technology to the water content measurement of in situ soil.However,all existing in situ applications of AHFO technology fail to consider the effect of soilesensor contact quality on water content measurements,limiting potential for the wider application of AHFO technology.To address this issue,the authors propose a method for determining the soilesensor thermal contact resistance based on the principle of an infinite cylindrical heat source.This is then used to establish an AHFO water content measurement technology that considers the thermal contact resistance.The reliability and validity of the new measurement technology are explored through a laboratory test and a field case study,and the spatial-temporal evolution of the soil water content in the case is revealed.The results demonstrate that method for determining the soilesensor thermal contact resistance is highly effective and applicable to all types of soils.This method requires only the moisture content,dry density,and thermal response of the in situ soil to be obtained.In the field case,the measurement error of soil water content between the AHFO method,which takes into account the thermal contact resistance,and the neutron scattering method is only 0.011.The water content of in situ soil exhibits a seasonal variation,with an increase in spring and autumn and a decrease in summer and winter.Furthermore,the response of shallow soils to precipitation and evaporation is significant.These findings contribute to the enhancement of the accuracy of the AHFO technology in the measurement of the water content of in situ soils,thereby facilitating the dissemination and utilization of this technology.

Influence of carbon content on wear resistance and wear mechanism of Mn13Cr2 and Mn18Cr2 cast steels

By means of impact abrasion tests, micro-hardness tests, and worn surface morphology observation via SEM, a comparison research based upon different impact abrasive wear conditions was conducted in this research to study the influence of different carbon contents(1.25 wt.%, 1.35 wt.%, and 1.45 wt.%) on the wear resistance and wear mechanism of water-quenched Mn13Cr2 and Mn18Cr2 cast steels. The research results show that the wear resistance of the Mn18Cr2 cast steel is superior to that of the Mn13Cr2 cast steel under the condition of the same carbon content and different impact abrasive wear conditions because the Mn18Cr2 cast steel possesses higher worn work hardening capacity as well as a more desirable combination of high hardness and impact toughness than that of the Mn13Cr2 cast steel. When a 4.5 J impact abrasive load is applied, the wear mechanism of both steels is that plastic deformation fatigue spalling and micro-cutting coexist, and the former dominates. When the carbon content is increased, the worn work hardening effect becomes increasingly dramatic, while the wear resistance of both steels decreases, which implies that an increase in impact toughness is beneficial to improving the wear resistance under severe impact abrasive wear conditions. Under the condition of a 1.0 J impact abrasive load, the wear mechanism of both steels is that plastic deformation fatigue spalling and micro-cutting coexist, and the latter plays a leading role. The worn work hardening effect and wear resistance intensify when the carbon content is increased, which implies that a higher hardness can be conducive to better wear resistance under low impact abrasive condition.

Resistivity is used as a tool to evaluate the variability of soil water content

Resistivity is used to evaluate soil water content(SWC),which has the advantages of not causing soil disturbance and in low price.It is an effective way to assess the SWC variability.This paper aims to evaluate the variability of loess slope SWC through the change of resistivity.It provides a simple way for long term SWC monitoring to solve the expensive cost of deploying moisture sensors.In this context,geoelectric and environmental factors such as soil temperature and SWC were monitored for three years.The prediction model of apparent resistivity and SWC was calibrated.The post processing of geoelectric data was introduced.In addition,the SWC collected by Time-Domain Reflectometry(TDR)was used to verify the feasibility of electrical resistivity tomography(ERT)data.The SWC variability in the process of rainfall,the evolution of four seasons,and the alternation of drying and wetting were evaluated.The research results show that:i)the SWC monitored by ERT and TDR can reflect the response and hysteretic effect of water content at 0.5-3.0 m depth.ii)The moisture content monitored by ERT reflects that the soil is relatively wet in summer and autumn and dry in winter and spring.iii)From 2017 to 2020,the SWC increased in August,and the soil became dry in January.iv)Two areas with high SWC and three areas with low SWC on loess slope are reflected by resistivity.The outcome can provide the change information of SWC to a great extent without excavating boreholes.

Application of Wenner Configuration to Estimate Soil Water Content in Pine Plantations on Sandy Land

To estimate the mean value of surface soil water content rapidly,accurately,and nonintrusively,field investigations on soil electrical resistivity(SER)with the Yokogawa 324400 earth resistivity meter and the surface(0-150 cm)soil water content(SWC)with time domain reflectometry(TDR),together with the abiotic factors including soil texture,structure. and salinity concentrations were conducted in the Mongolian pine(Pinus sylvestris var.mongolica)plantations on a sandy land.The measurement of SER was based on the 4-probe Wenner configuration method.Relationships between the values of SWC and SER were obtained based on analysis of the abiotic factors of the research site,which play a key role in affecting the soil electrical resistivity.Results indicate that the SER meter could be used to estimate the mean value of SWC in the Mongolian pine plantations on the sandy land during the growing seasons.The bulky nature of the equipment simplified the cumbersome measurements of soil water content with the general methods.It must be noted that the Wenner configuration method could only provide the mean values of the SWC,and the soil texture,structure, temperature,and solute concentrations influenced the SER and further affected the estimation of the SWC by the SER meter.Therefore,the results of this study could be applied on a sandy land during the growing seasons only.However, the SWC of other soil types also may be obtained according to the individual soil types using the procedures of this study.

Relationship Between Physiological-biochemical Changes Under Drought Stress and Drought Resistance in Ramie

A study on the physiological-biochemical changes of different ramie(Boehmeria Jacq. ) varieties under drought stress was carried out, the results showed that relative water contents(RWC) decreased and RPP increased with the increase of drought stress. Compared with drought sensitive varieties, drought resistant varieties had higher RWC in leaves but lower RPP. Peroxidase activity of drought-resistance varieties changed from low to high whereas sensitive ones changed in opposite direction. Proline contents of drought sensitive varieties was higher than those of drought resistant ones under a certain degree drought stress. Proline accumulation in drought resistant varieties was faster than that in drought sensitive ones under serious drought stress.MDA contents in leaf was increased under drought stress. MDA contents increased slowly in resistant varieties while that increased rapidly in sensitive ones.

断层虚位错模式揭示的2022年1月8日青海门源M_(S)6.9地震前的地电阻率变化

选取2022年1月8日青海门源M_(S)6.9地震震中400 km范围内四个地电阻率观测台站的观测精度高、具有稳态年变、震前无显著干扰的地电阻率ρ_(s)观测数据,结合ERA5同化数据集中的多层土壤温度和土壤水分含量,在利用多项式拟合获取各台站(或测道)地电阻率正常年动态的基础上,分析了门源地震前地电阻率的异常变化。结果显示:金银滩台EW测道、武威台NS测道和山丹台EW测道、N45°W测道震前存在超阈值的异常变化,并呈现各向异性特征。基于断层虚位错模式分析了地电阻率异常变化与孕震过程之间的联系,结果表明:金银滩台震前处于压缩区并受到NNE方向的挤压,与主压应变近似正交的EW测道于震前10个月出现负异常;同样位于压缩区的武威台,受到了ENE向的挤压,NS测道的地电阻率在孕震早期(震前13个月)以负异常为主,孕震中晚期(震前3个月)出现了正异常;山丹台,位于膨胀区,受到近似NS向的拉张,与主张应变平行的NS测道未发现异常,但EW测道震前一年地电阻率出现正异常,N45°W测道的地电阻率也在震前半年左右出现超阈值并呈正异常。此外,金银滩台、山丹台和武威台距离门源地震震中的距离分别为92 km,113 km和139 km,相应的地电阻率异常最大变化幅值分别为−3.0σ,2.2σ和−2.1σ。此外,门源地震前地电阻率异常变化的时空特征与岩石实验结果及理论模型一致,也符合震源区应力应变积累程度较高、向外围方向逐渐衰减的分布特征。由此推断,2022年门源M_(S)6.9地震前地电阻率的时空变化可能与区域介质变形及应力变化有关。

含水率影响下路基压实多场耦合数值模拟

研究目的:智能压实作为新兴技术已开始应用于路基工程中,并为施工建设带来了巨大便利。但研究和实践表明,未考虑土体含水率的制约因素已成为影响智能压实测试结果精度的主要原因之一。利用电阻率测试方法实现土体含水率的实时检测,本文模拟在振动压路机振动轮上安装测试电极,建立路基土体的流-固-电耦合分析模型,对不同含水率、激振力条件下的路基变形及电场分布规律开展研究。研究结论:(1)推导得出了路基智能压实过程中,土体应力场、水分场、电场多场耦合方程,利用COMSOL软件建立了数值分析模型,为路基智能压实分析研究提供了一种有效方法;(2)路基的压实变形受土体含水率影响明显,随含水率增加,路基沉降量增加,较大激振力可增加路基的压缩变形量;(3)当增加激振力大小,土体最终含水率数值减小,低于最佳含水率的土体受激振力影响最小,高于最佳含水率的土体受激振力影响最大;(4)路基电阻率随含水率增加而减小,相同土体含水率情况下,较大激振力下的土体电阻率及影响范围小于较小激振力情况;最佳含水率时,激振力大小对电阻率的影响最小;(5)本研究结论可为路基智能压实的发展和推广提供理论和技术支持。

海洋软黏土不排水循环强度的触变性试验研究

以长江入海口海域软黏土为研究对象,开展了系列不固结不排水循环三轴试验,研究了静置时间T、含水率w及塑性指数IP对重塑海洋软黏土不排水触变循环强度的影响。试验结果表明:以双幅轴向应变εad=5%为重塑海洋软黏土试样的失效判据,破坏振次为15的循环强度CRR15随T的增加而增大,T=14 d,CRR15的增长速度最快,T>28 d时CRR15增加略有上升或趋于稳定。前期扰动或循环荷载的施加会导致软黏土触变性减弱,软黏土的触变循环强度比Ad明显小于静剪强度比As。Ad随IP的增加先增大后降低,随w的增加而增大,随归一化含水率w/wL的增加先增大后减小,当w/wL=0.76时,Ad达到最大值。开展平行工况的无侧限抗压强度试验,提出以循环轴应力幅值σd与2倍无侧限抗压强度qu之比σd/2qu表征循环应力水平,发现σd/2qu与不同w及T的试样达到εad=5%所需的破坏振次N_f存在唯一性关系,且σd/2qu随N_f的增大呈幂函数减小。

不同灌水处理对春玉米土壤水分、耗水特征及产量的影响

【目的】探究不同灌水定额对春玉米全生育期耗水特征及产量的影响,优化克拉玛依地区春玉米节水灌溉制度,以提高当地水分利用效率。【方法】于2021年5—9月在克拉玛依农业综合开发区开展春玉米田间试验,设置6个灌水处理W1(225 m^(3)/hm^(2))、W2(300 m^(3)/hm^(2))、W3(375 m^(3)/hm^(2))、W4(450 m^(3)/hm^(2))、W5(525 m^(3)/hm^(2))、W6(600 m^(3)/hm^(2)),探究不同灌水定额对春玉米耗水特征及产量的影响。【结果】①各生育期不同灌水处理0~100 cm土层土壤含水率随土层深度增加呈“增-减-增”的变化趋势。W5处理在喇叭口期、抽雄散粉期、乳熟期、完熟期较W1、W2、W3、W4、W6处理0~100 cm土层土壤贮水量平均增加了2.35%~9.11%、0.21%~4.37%、0.39%~1.79%、0.60%~4.48%。②完熟期W5处理百粒质量显著高于W1处理和W2处理,但与W3、W4、W6处理无显著性差异。W5处理穗粒数较其他处理显著提高10.49%~36.01%,穗长较其他处理显著提高8.31%~27.12%。③综合评判模型计算得出W5处理(525 m3/hm^(2))综合评价指数最高。【结论】因此,全生育期灌水10次,灌水定额为525 m3/hm^(2)是克拉玛依地区最优灌水处理。

水盐含量及电阻率对盐渍土抗剪强度的影响

为了研究盐渍土的水盐含量及电阻率对其抗剪强度的影响,对长岭县的盐渍土进行室内试验,测量了不同深度土壤的含水率、含盐量、电阻率和抗剪强度,研究了电阻率和抗剪强度与含水率含盐量的关系。结果表明:盐渍土的电阻率随含盐量和含水率的增加而逐渐降低;经三轴剪切试验可得,内摩擦角和黏聚力均随含盐量的增加而减小,与含水率呈负相关;盐渍土的抗剪强度与电阻率之间具有良好的线性关系,抗剪强度随电阻率的增大而逐渐增大,构建盐渍土抗剪强度与电阻率之间的相关拟合公式,对实际工程应用有理论参考意义。

窄河道砂高含水井侧钻地质设计优化与应用——以大庆外围葡萄花油层为例

针对窄河道砂高含水井超短半径水平侧钻后含水上升快的问题,通过优化入层距、侧钻方向、水平段长度、完井方式等影响因素,形成窄河道砂高含水井侧钻优化设计技术;并在此基础上,综合考虑地质参数、生产动态、数模预测结果,建立了窄河道砂高含水井侧钻选井、选层标准。现场实施结果表明,窄河道砂高含水井侧钻后含水上升速度明显减缓,可实现较好的降水增油效果。该研究结果可为高含水长关低效井治理提供重要的技术支撑。

高掺量胶粉/SBS改性沥青及其混合料的路用性能

为了提高废旧轮胎利用率,降低沥青生产成本,发挥胶粉和SBS两种改性沥青的优势,通过优化制备工艺和材料掺量,研究沥青的三大指标、黏度、弹性恢复、储存稳定性,确定了胶粉/SBS复合改性沥青的胶粉最佳掺量为42%,裂解剂的最佳掺量为1.5%。以制备的高掺量复合改性沥青混合料为主要研究对象,其他5种沥青混合料为对照组,包括基质沥青混合料、3%SBS改性沥青混合料、21%普通掺量的胶粉改性沥青混合料、42%高掺量胶粉改性沥青混合料以及21%胶粉+3%SBS普通掺量复合改性沥青混合料,通过车辙试验、低温小梁弯曲试验等分析各个改性沥青混合料的性能。结果表明,比起其他5种沥青混合料,高掺量胶粉/SBS复合改性沥青混合料有优异的高温抗车辙、低温抗开裂和水稳定性,为进一步研究胶粉/SBS改性沥青的应用起到了推广作用。

不同温度和胁迫时长下蓝云杉的光合响应

[目的]全球气候持续变暖将不利于蓝云杉生长,研究蓝云杉在高温胁迫下的生长、光合响应机制,为蓝云杉引种栽培提供参考。[方法]以五年生蓝云杉苗为试验材料,设定45、50、55℃3种温度,处理6 h;其中45℃处理还有12、18、和24 h不同时长,常温(25℃)作为对照。研究处理后、恢复7和28 d的生长表型、针叶含水量和叶绿素荧光参数,分析高温、胁迫时长对蓝云杉生长和光合作用的影响。[结果]45℃处理6 h蓝云杉基本可以恢复正常生长,而50℃和55℃处理的蓝云杉整株针叶都变黄,干枯掉落,伴随着相对含水量的降低,且光系统Ⅰ(PSⅠ)有效量子产量实际光化学效率(Y(Ⅰ))、PSⅠ相对电子传递速率(ETR(Ⅰ))、由供体侧限制引起的PSI处非光化学能量耗散的量子产量(Y(ND))、受体侧非光化学能量耗散产生的量子产量(Y(NA))、光系统Ⅱ(PSⅡ)有效量子产量实际光化学效率(Y(Ⅱ))、PSⅡ相对电子传递速率(ETR(Ⅱ))、PSⅡ的最大光化学效率(F_(v)/F_(m))和用于电子传递的量子产额(φE_(o))均显著低于45℃处理和对照。尽管45℃处理6、12、18、24 h后从表型上看不出蓝云杉的形态发生明显变化,但是恢复期发现12、18 h针叶继续失水、变黄,24 h处理整株针叶都变黄,基本干枯掉落,针叶相对含水量降至最低。恢复28 d时,18、24 h的荧光参数φE_(o)几乎为0,电子传递受到了抑制。[结论]胁迫时长为6 h,蓝云杉可以耐45℃高温处理,不耐50、55℃高温。45℃高温处理时长超过12 h苗木失水严重,针叶干枯,对光合特性产生了显著影响,难恢复正常生长。

水泥稳定再生骨料混合料力学性能和抗冻性能研究

为促进再生骨料在半刚性基层中的应用,实现建筑垃圾在公路工程中的资源化利用,本文采用等质量置换法,系统分析了再生骨料掺量(质量分数)为0%、30%、50%、70%、100%时对无机混合料最大干密度、最佳含水率、无侧限抗压强度、抗冻性能的影响,并从微观角度解释了内在影响机理。结果表明:掺入再生骨料降低了无机混合料的最大干密度,增大了最佳含水率;再生骨料可以有效提高无机混合料的无侧限抗压强度和抗冻性能,当再生骨料掺量为70%时提升效果最佳,此时再生骨料无机混合料7、28 d无侧限抗压强度为4.6、6.8 MPa, 28、90 d冻融循环后残留抗压强度比可达82.4%、85.5%。

水流作用下混凝土表面剪切力及其冲磨特性的试验研究

为了获得水流作用下混凝土表面剪切力和抗冲磨强度的变化规律,以水泥砂浆替代混凝土,设计制备环形试件作为研究对象,将一部分试件浸入1 mol/L的氯化铵溶液浸泡,以得到表层具有不同溶蚀程度的环形试件,再利用自主设计的水流冲刷试验装置,开展试件在不同条件下的水流冲刷试验,分析水流流速、含砂率和溶蚀程度等参数对试件表面剪切力的影响以及试件抗冲磨强度的变化。结果表明:水泥砂浆试件表面剪切力随流速和含砂率的增大而增大,且与流速的1.70次方成正比;溶蚀后试件的表面剪切力比未溶蚀试件有明显增加,随着溶蚀程度的提高,试件表面剪切力也有一定增加;试件抗冲磨强度随着溶蚀程度和冲刷流速的增大而降低。

水分对混合动力汽车发动机油性能的影响

利用机械搅拌机将蒸馏水均匀分散在发动机油中,形成“油包水”结构的稳定乳化液,利用石油产品低温泵送黏度测定法、铜片腐蚀测定法、润滑油氧化诱导期测定法、倾点测定法、四球法分别评价水分对混合动力汽车发动机油理化性能的影响。试验结果表明:水分对油品的低温泵送黏度、氧化诱导期、最大无卡咬负荷、烧结负荷及磨斑直径等性能有影响,随着水含量的增加,其油品的低温流动性、抗氧化性、承载能力及抗磨损性能变差;对油品的倾点、腐蚀性能基本无影响。(图0表5参考文献5)

基于不同功率的非能动安全壳热量导出系统实验研究

“华龙一号”非能动安全壳热量导出系统(passive containment heat removal system,PCS)和“玲龙一号”非能动安全壳热量导出系统设计原理相同,但系统功能和设计准则不尽相同。为了掌握影响系统换热能力和运行的关键因素,本文结合不同项目的特点,从综合性能实验需求和实验结果等方面,研究、分析“华龙一号”非能动安全壳热量导出系统与“玲龙一号”非能动安全壳热量导出系统设计中的典型现象,发现降低冷却水箱水位可以提升系统的换热能力、改变冷管段阻力对系统的换热能力更敏感和冷管段隔离阀关闭方案在开启时可能会有一定的风险,从而提出后续优化研究和设计中需要重点关注的影响因素。文中结论可用于指导相关系统设计工作。

川南长宁地区奥陶系五峰组—志留系龙马溪组页岩气储层低电阻率响应特征及主控因素

以川南长宁地区NX22井五峰组—龙马溪组低电阻率页岩气储层为例,利用岩心矿物组分、扫描电镜、总有机碳(TOC)含量、含水饱和度测试及测井曲线等资料,确立了低电阻率页岩气储层岩石体积物理模型,采用随机法构建了三维数字岩心模型,进而利用有限元数值模拟方法模拟计算各矿物组分含量、含水饱和度及有机质石墨化的电阻率响应特征,并分析其主控因素。研究结果表明:(1)长宁地区五峰组—龙马溪组低电阻率页岩气储层岩石体积物理模型由骨架(石英、长石、方解石和白云石等)、黏土矿物、黄铁矿、未石墨化有机质以及石墨化有机质、孔隙6个部分组成。(2)三维数字岩心模型的长、宽、高分别为100×100×100像素,融入了上述物理模型中的6个部分,并采用不同的颜色对导电组分进行标识,可以显示不同方向上的切片,表征低电阻率页岩气储层的组分特性。(3)黏土矿物含量、黄铁矿含量、含水饱和度以及有机质石墨化程度等4个参数增大都会造成页岩气储层的电阻率下降,而有机质的高石墨化程度(25%)和高含水饱和度(88.0%)使页岩气储层的电阻率从正常电阻率(大于15Ω·m)降到低阻甚至超低阻(小于5Ω·m),是导致研究区页岩气储层超低阻响应的2个核心因素。

考虑尺寸效应的红黏土电阻率特性及其模型研究

【目的】探究不同尺寸土样对电阻率带来的影响。【方法】以云南地区红黏土为研究对象,制备不同含水率、干密度和几何尺寸的重塑红黏土,研究不同几何尺寸下电阻率特性变化关系,构建合理、可靠且适用于不同几何尺寸红黏土的电阻率模型。【结果】相同条件下,电阻率随着含水率增加而降低,随着孔隙率增大而增大,随着体积含水率的增大而减小;几何尺寸的变化使土体孔隙结构和饱和度分布变化,引起电阻率变化,呈现几何尺寸增大,电阻率增大趋势;根据多元线性回归分析得到红黏土电阻率影响因素相关性依次为:几何尺寸、含水率、孔隙率;基于电阻率特性变化关系,构建适用于不同几何尺寸大小的电阻率体积含水率模型,该模型拟合精度高。【结论】该实验为高密度电法无损快速且经济的预估尺寸体积差异化的红黏土区域含水率提供途径与参考。

Effects of Water Stress on Leaf Water and Chlorophyll Fluorescence Parameters of Sugarcane Seedling

[Objective] The aim was to explore the effects of water stress on leaf water and chlorophyll fluorescence parameters of sugarcane seedling,as well as to provide basis for the study on sugarcane production and evaluation. [Method] Seven different sugarcane varieties were studied at the seedling stage under drought stress,and the changes of leaf water and chlorophyll fluorescence parameters under stress conditions were detected. [Result] leaf water potential,leaf relative water content and soil relative water content showed a certain amount of internal relationship,the sugarcane varieties that had more tolerant to drought had higher utilization rate of soil water; the correlation analysis and factor analysis suggested that the survival rate at seedling stage under drought stress,Fv/Fm,leaf water potential and relative water content could be used as drought resistance evaluation indicators. [Conclusion] As a relatively independent influencing factor,water potential had dominating effect on drought resistance,and the reliability of Fv/Fm as drought resistance evaluation indicator had been verified.