Impact of Initial Soil Conditions on Soil Hydrothermal and Surface Energy Fluxes in the Permafrost Region of the Tibetan Plateau

Accurate initial soil conditions play a crucial role in simulating soil hydrothermal and surface energy fluxes in land surface process modeling.This study emphasized the influence of the initial soil temperature(ST)and soil moisture(SM)conditions on a land surface energy and water simulation in the permafrost region in the Tibetan Plateau(TP)using the Community Land Model version 5.0(CLM5.0).The results indicate that the default initial schemes for ST and SM in CLM5.0 were simplistic,and inaccurately represented the soil characteristics of permafrost in the TP which led to underestimating ST during the freezing period while overestimating ST and underestimating SLW during the thawing period at the XDT site.Applying the long-term spin-up method to obtain initial soil conditions has only led to limited improvement in simulating soil hydrothermal and surface energy fluxes.The modified initial soil schemes proposed in this study comprehensively incorporate the characteristics of permafrost,which coexists with soil liquid water(SLW),and soil ice(SI)when the ST is below freezing temperature,effectively enhancing the accuracy of the simulated soil hydrothermal and surface energy fluxes.Consequently,the modified initial soil schemes greatly improved upon the results achieved through the long-term spin-up method.Three modified initial soil schemes experiments resulted in a 64%,88%,and 77%reduction in the average mean bias error(MBE)of ST,and a 13%,21%,and 19%reduction in the average root-mean-square error(RMSE)of SLW compared to the default simulation results.Also,the average MBE of net radiation was reduced by 7%,22%,and 21%.

Initial excess pore water pressures induced by tunnelling in soft ground

Tunnelling-induced long-term consolidation settlement attracts a great interest of engineering practice. The distribution and magnitude of tunnelling-induced initial excess pore water pressure have significant effects on the long-term consolidation settlement. A simple and reliable method for predicting the tunnel-induced initial excess pore water pressure calculation in soft clay is proposed. This method is based on the theory of elasticity and SKEMPTON's excess pore water pressure theory. Compared with the previously published field measurements and the finite-element modelling results, it is found that the suggested initial excess pore water pressure theory is in a good agreement with the measurements and the FE results. A series of parametric analyses are also carried out to investigate the influences of different factors on the distribution and magnitude of the initial excess pore water pressure in soft ground.

Influence of Initial Water Content on Synthesis of Silicalite-1 Zeolite

The effect of initial water content on the synthesis of silicalite-1 zeolite and its reaction performance in methanol to propylene(MTP) reaction was comprehensively investigated. The as-synthesized samples were characterized by XRD,N_2 adsorption and desorption, SEM, and FTIR techniques, and studied for the methanol to propylene(MTP) reaction. The results showed that the initial water content played a crucial role on the particle size and porous structure of the silicalite-1 zeolites. It was found that adding initial water to reach a certain amount, the crystal size reduced obviously and the mesoporous structure appeared. Upon applying the silicalite-1 zeolite samples in the MTP reaction, they showed excellent catalytic performance to reach a highest propene mass yield of 26.81%(on the CH_2 basis) and a P/E ratio of 6.28 in 2 h. The excellent catalytic performance of silicalite-1 can be attributed to its mesoporous structure.

Modeling Virgin Compression of Reconstituted Clay at Different Initial Water Contents

The observations on compressibility of reconstituted clays show that the compression line with a higher initial water content lies above the compression line with a lower initial water content for a given clay. Hence there exists additional void ratio due to initial water contents among virgin compression lines（VCLs） of reconstituted clays. In this paper, the difference in void ratio caused by different initial water contents is investigated based on the empirical equation proposed by Liu and Carter（2000） for describing the differential void ratio at the same stress between natural and reconstituted clays. The mechanism of compressibility of reconstituted clays, when the stress level is larger than the remolded yield stress, is also discussed.

REMOTE SENSING APPLICATION RESEARCH OF WATER POWER AT THE INITIAL EXPLOITING STAGE IN THE LOWER REACHES OF YALONG RIVER

There are abundant water power resources in the Yalong River which are suitable for the large hydroelectric engineering. But a reliability study should be made for the valley which liable to frequent earthquakes. The color infrared aerophotos, multi-spectral photography and thermal infrared scanning had been specially done besides MSS image, processing. Researches on remote sensing applications to engineering geology, hydrogeology, deformation of neo-tectonics, Iandslide, mud-rock flow, ecological environment and geographical information system had been carried out by more than 20 research units.

SWOT Analysis and Challenges of Nile Basin Initiative:An Integrated Water Resource Management Perspective

River Nile is one of the longest transboundery rivers and it is shared and used by Burundi,Democratic Republic of Congo,Egypt,Ethiopia,Eritrea,Kenya,Rwanda,Sudan,Tanzania and Uganda.As of today,the Nile is a crucial resource for the economic development of the Nile Basin countries and a vital source of livelihood for 160 million inhabitants as well as 300 million people living in the 10 riparian countries.The Nile Basin Initiative(NBI) is one of the international cooperative river basin management program and regional partnership where all the Nile Basin countries except Eritrea unite to pursue long-term sustainable development,improved land use practices and management.This review therefore focused on the challenges not faced on NBI in terms of integrated use of the river and conducted analysis of strengths,weaknesses,opportunities and threats(SWOT) based on secondary data.The result of the review revealed that for decades,the Nile Basin people have been facing many complex environmental,social,economic and political challenges that have made it difficult for the proper management and sustainability of Nile water.The initiative provides training to develop skills in government ministries,non-governmental organizations and local communities in each country.It is also working to raise awareness of critical environmental issues by strengthening networks of environmental education practitioners;developing curriculum in the education sector.The challenges of NBI include the involvement and funding of World Bank,lack of sufficient staff,procedural and policies conflicts,lack of coordination and linkage with other regional institutions and lack of recognition as river basin organization.Considering the complex nature of the project,it is recommended that the NBI should come up with a strong multi-disciplinary monitoring and evaluation team to follow up all implemented projects.The NBI should carry out participatory land use planning in communities along the river basin.Moreover,livelihood analysis should be carried out especially in communities along the Nile to come up with poverty eradication projects which are socially acceptable,applicable,economically viable and affordable.

Leak-off behavior and water shut-off performance of a polymer/chromium(Cr^(3+)) gel in fractured media

During gel treatments for fractures, the leak-off behavior of gelant has a great effect on the water shut-off performance of gel. Experiments were carried out using a polymer/chromium(Cr^(3+)) gel system to explore the leak-off behavior and the water shut-off performance of gel in fractured media. Results of the gelant leak-off study show that the gelant leak-off from fracture into matrix contributes to the formation of the gelant leak-off layer during the gelant injection. Moreover, because of the gradual formation of the gelant leak-off layer along fracture, the initial leak-off ratio of gelant is relatively high, but it declines and finally levels off with the increase of the injection volume. The polymer concentration of gelant has a great effect on the chromium output in fluids produced from fractures. With the increase of the polymer concentration, the chromium concentration first decreases and then increases, and the leak-off depth of gelant into matrix is gradually reduced. Results of the water shut-off study present that the decrease of the chromium concentration inside the fracture greatly reduces the water shut-off performance after the gel formation. Therefore, because of the relatively high degree of chromium leak-off, enough injection volume of gelant is essential to ensure the sufficient chromium concentration inside the fracture and to further achieve a favorable water shut-off performance. On the premise of gel strength assurance inside the fracture, the water shut-off performance of gel gradually declines with the extension of the distance from the fracture inlet, and different leak-off degrees of gelant along the fracture are responsible for this phenomenon. Therefore, a proper degree of gelant leak-off contributes to enhancing the water shut-off performance of gel for fractures.

深水气田长距离混输模式下水相运动规律研究

陵水25-1深水气田混输管道距离长、管道爬坡段坡度大,初始投产阶段混输流体水相到达平台的时间长且预测困难,给管道安全运行带来风险。基于多相流计算模型,运用LedaFlow软件,对陵水25-1深水气田初始投产阶段的水相运动规律进行研究,并深入分析含水率、油量、气量、油水相间摩擦系数等因素对水相运行的影响。结果表明:初始投产阶段水相在爬坡段分离和积聚,形成长时间的停滞,管道坡度越大,水相波动越剧烈;含水率越高的物流,水相在爬坡段聚集时间越短;气量增大则会降低水相滞液程度,提高水相运行速度,有助于水相爬坡;油量变化对水相运行速度的影响较小,油水相间摩擦系数对爬坡段水相运动有直接影响,油水相间摩擦系数修正拟合,对实际管道运行有重要指导意义。研究结果可为深水气田开发研究提供借鉴。

我国用水权交易现状与制度构建

为促进《关于推进用水权改革的指导意见》提出的于2035年全面建立归属清晰、权责明确、流转顺畅、监管有效的用水权制度体系的工作目标,针对我国用水权交易仍存在初始分配制度不健全、交易定价机制不完备、用水监测计量与监管尚需加强的现状,分析了现行用水权交易制度存在的问题,在明确用水权交易内涵的基础上,提出用水权交易制度的构建应当利用哈贝马斯的商谈理论指导用水权初始分配,兼顾经济利益与生态利益构建标准多元、基准有别的定价机制,建立巡查与抽查制度完善的用水监测计量与监管的具体制度设计。

流域初始水权分配的主从递阶双层优化方法

依托“流域-地区-行业”层次的初始水权分配模式,“流域-地区”层次影响制约“地区-行业”层次的初始水权分配,“流域-地区”和“地区-行业”层次的初始水权分配共同影响流域综合效益。现有研究主要聚焦“流域-地区”或“地区-行业”层次的初始水权分配,但将两个层次集成进行初始水权分配仍有待深化研究。为此,构建主从递阶双层优化方法,开展流域初始水权分配研究。具体可表述为:①针对“流域-地区”层次,建立流域综合效益优化函数与约束条件。构造适应性诊断准则和空间均衡性诊断准则,嵌入流域综合效益优化函数中,提高地区之间初始水权分配与经济社会发展的适应性、流域分水的空间均衡性。②针对“地区-行业”层次,建立地区综合效益优化的非线性目标规划模型,保障行业发展用水需求。并构造匹配性诊断准则嵌入非线性目标规划模型中,提高地区不同行业初始水权分配与行业发展的匹配性。③集成“流域-地区”和“地区-行业”层次,应用主从递阶双层优化方法,开展黄河流域初始水权分配实践探索。研究得出:通过黄河流域初始水权分配方案设计,得到黄河流域涉及省区水权分配比例与其经济社会发展综合指标加权值比例的比值,其中,内蒙古-陕西、陕西-宁夏、宁夏-山西、山西-河南、河南-甘肃、甘肃-青海、青海-山东分别为0.84、1.45、0.84、1.08、1.19、1.77、1.02,满足适应性诊断准则。黄河流域初始水权分配的基尼系数为0.10,属于“空间均衡度很高”,满足空间均衡性诊断准则。黄河流域涉及省区不同行业的水权配置与行业发展的匹配度均超过0.90,属于“高度匹配”。同时,黄河流域经济、社会、生态效益优化函数对应的满意度分别达到0.946、0.943、1.000,黄河流域涉及省区的经济、社会、生态效益优化函数对应的满意度均超过0.90。结果表明,该方法能够有效破解流域初始水权分配难题。为保障流域初始水权分配方案的有效落实,必须强化水资源刚性约束和双控行动,提升流域水利科技创新能力,推进流域产业用水结构合理化与产业结构高级化。

不同应力水平下给定含水率混凝土低温有效预压性能试验研究

为评估低温储罐类预应力混凝土结构设计及安全性能,通过对混凝土施加各种初始预压应力水平(0.2、0.3、0.4、0.5、0.6及0.7)并在-160℃低温作用下的试验,系统地探讨其有效预压性能变化规律,同时比较较高和正常两种较为典型混凝土含水率情况对其影响差异。结果表明,随施加的初始预压应力水平提高,混凝土降温点和温均点时的有效预压应力损失率均呈下降的变化趋势,而其降温段和恒温段时的有效预压应力变化率的变化较为复杂;混凝土达其降温点后恒温阶段的有效预压应力损失均有所恢复,且随初始预压应力水平的提高其恢复程度更加明显;含水率对不同初始预压应力水平混凝土低温作用下降温点和恒温点时的有效预压应力损失率变化趋势未产生影响,仅使其变化程度有较明显的差异。

高温作用下非饱和黄土裂隙演化及其定量分析

黄土地区采用热减湿工法加固基坑边坡具有潜在应用价值,科学评价高温减湿黄土的裂隙演化是验证该加固工法可行性的关键环节。利用自制试验装置,进行了不同初始干密度和初始含水率的非饱和黄土在50~200℃温度水平下的裂隙演化试验,观察了土样含水率和表层裂隙变化,通过试验图像处理定量分析了裂隙率r、裂隙总长L、分形维数D、裂隙平均宽度W等裂隙指标随温度的变化规律。分析结果显示:随着温度水平提高,r、L、D均有所提高,W变化不明显;初始干密度的提高使r、L、D明显减小,使W明显提高;初始含水率的升高使r、L、D、W显著提高。高温作用显著改变土体的起裂模式,100℃临界温度作用下土体的起始裂隙快速出现,这可能与高压水蒸气的不均匀挤压有关。高温极大加快裂隙演化进程,但超过100℃后,继续升温对裂隙演化的加速幅度不大。从断裂力学的角度分析了高温作用下黄土裂隙开裂和扩展的力学机制,揭示了高温黄土裂隙演化机制。基于基质吸力对裂隙演化的重要影响,建立了考虑高温的基质吸力公式,在一定程度上揭示了高温对基质吸力的显著影响。

大型地下厂房水压致裂法地应力测量及地应力场反演分析

岩体初始地应力是地下工程研究中的重要内容,依托大型地下厂房工程,采用三维水压致裂法和常规水压致裂法对洞内孔ZK1和地表孔ZK2分别进行地应力测量,获得岩体初始地应力;基于实测数据利用三维数值模拟方法进行地应力场反演计算,获得所需工程区的地应力场分布规律。研究表明:水压致裂法可以有效地获得初始地应力,三维水压致裂法获得的地下应力情况更为准确且可以与垂直孔测试数据互相印证;数值模拟获取的地应力计算值和实测值具有一致性,厂房隧洞布置较为合理且工程区发生岩爆概率较低;现场原位测试结果与回归地应力场分布规律可为工程设计提供有效的科学支撑。

汛期洪水资源化利用对三峡水库淤积影响研究

作为三峡水库诸多优化调度方式中的一种,洪水资源化利用对水库淤积的影响受到持续关注,开展针对场次洪水的相关研究有助于进一步深化对水库淤积科学问题的认识,有望为调度工作提供一定的技术支撑。通过2013年以来的历史水文资料分析与水沙运动数值模拟,探究了入库洪水的输沙过程以及洪水资源化利用对库区淤积与水库排沙的影响。结果表明:洪峰流量介于30000~55000 m 3/s的中小洪水是近年三峡入库洪水的主要形式,随着入库洪峰流量的增加,洪水的地区组成逐渐趋向于金沙江下游、嘉陵江共同主导;常年回水区淤积、水库排沙是“消化”入库泥沙的两种主要途径,且以前者的作用为主;针对Ⅰ-3类入库洪水,坝前起调水位Z 0的抬升或洪水资源化利用对水库淤积的影响主要在于造成了库区淤积的重分布,次要在于改变了水库的排沙作用,在Z 0≤150 m条件下,洪水资源化利用对水库淤积的影响相对较小;针对典型洪水,当武隆洪峰流量Q′WL与入库洪峰流量Q′RK的比值小于1/5(即Q′WL/Q′RK<1/5)且朱沱洪峰流量Q′ZT与北碚洪峰流量Q′BB的比值介于3/2和3之间(即3/2<Q′ZT/Q′BB≤3)时,在Z 0=145 m情景下,洪水量级的提高增加了约50%的入库沙量,而水库调度抬升的库水位不足坝前水深的5%,导致前者较后者产生了更加严峻的变动回水区淤积和水库排沙情势;随着嘉陵江的洪水输沙作用逐渐显著,变动回水区,尤其是嘉陵江与长江干流交汇口下游河道的淤积情势愈发明显,应当予以重视。

紫外光引发制备PAA/CMC高吸水树脂及性能研究

以羧甲基纤维素钠(CMC)为骨架,通过紫外光引发聚合将单体丙烯酸(AA)接枝到CMC骨架上,合成PAA/CMC高吸水树脂。采用单因素实验法优化并确定了具有最高吸水能力的树脂的最佳制备条件。结果表明,合成树脂的最优条件为:CMC用量为0.05 g,AA质量浓度为0.48 g/mL,中和度为40%,引发剂和交联剂的用量分别为AA质量的0.3%和0.05%,反应时间55 min。所制备的高吸水树脂在蒸馏水中的最大吸水倍率为1281.21 g/g,在生理盐水中的最大吸水倍率为69.42 g/g。采用红外、热重以及扫描电镜对树脂的结构进行表征。结果表明,该制备方法成功合成了PAA/CMC高吸水树脂,其具有较好的热稳定性,树脂表面有明显的褶皱结构,具有吸水速率快、保水性好等特点。

无石棉纤维水泥平板的透水性的比较研究

论文讨论了无石棉纤维水泥平板底材对透水性的影响因素,比较了三种使用量最大的底材的外观和特性,介绍了它们的差异和优缺点。测试了三种底材在不同时间的透水值,讨论了透水值的大小和离散程度,评价了底材的质量。通过比较和分析探讨出底材的初始透水性值可能是影响透水性的关键因素。

建筑涂料在不同底材上透水性的结果分析和机理研究

总结了涂料透水性的影响因素,比较了涂料在不同底材上透水性规律和差异,对透水性试验底材的选用提出了建议。另外本文还从微观分析的角度,分析了底材的红外光谱、热失重曲线和X射线衍射结果,剖析了底材中的成分;从成分的角度说明了不同底材的联系和区别。

基于FLAC^(3D)原理模拟斜井支护效果研究

【目的】斜井介于平港和竖井之间,结构受力具有一定的复杂性,因此研究斜井硐室开挖和支护的有效性和可行性尤为重要,有必要对斜井支护效果展开研究。【方法】采用FLAC^(3D)对斜井围岩变形及支护技术方案的应力场、位移场和塑性区的分布变化情况进行数值模拟分析。【结果】在斜井开挖过程中,未支护工况下城门型斜井拱腰、拱顶、拱脚及底板等三处是开挖围岩最不稳定区域。支护后的围岩应力场、位移场和塑性区的分布减少了较多,其中,拱顶下沉位移量从57 mm降至5.3 mm;拱腰处水平位移量从26.7 mm降至15.7 mm;底板水平位移量从11.3 mm降至7.14 mm。【结论】在支护工况下的围岩应力场、位移场和塑性区的分布得到了较好改善,对斜井围岩的位移变形、塑性区范围起到了显著的控制作用。