薄土夹层作为围堰封底层的降水可行性与阻水效应研究

【目的】为了探究含薄土夹层的水下砂层作为桥墩围堰封底层时的降水可行性及其阻水效应问题,【方法】采用FLAC^(3D)分别模拟分析了混凝土封底和薄土夹层封底围堰施工的全过程,并分析了薄土夹层厚度、渗透系数、连续性、钢管桩长度、薄土夹层顶与钢管桩底距离、混凝土垫层厚度变化等对围堰钢管桩水平变形、坑底隆起变形及坑底渗水量的影响。【结果】结果表明:有、无薄土夹层时钢管桩均在围堰主墩施工完成阶段在桩顶以下14 m处达到最大水平变形,且分别为16.36 mm和20.72 mm,均满足规范要求;在薄土夹层厚度为4 m、渗透系数为5×10^(-9)cm/s、薄土夹层沿水平方向跨度为55 m、钢管桩长度为40 m、薄土夹层顶与钢管桩间距为0 m、混凝土垫层厚度为3 m的情况下,薄土夹层的阻水效果最好。【结论】薄土夹层具有很好的阻渗性,其作为围堰封底层进行降水施工是可行的,相关研究成果可为类似的工程提供参考和借鉴。

北方土石山区薄土坡耕地石坎反坡阶措施减流减沙效益分析

为解决我国北方土石山区薄土坡耕地水土流失问题,通过布设标准径流小区来研究石坎反坡阶措施的水土保持综合效果。结果表明:石坎反坡阶措施对于坡耕地水土流失调控效果显著,该措施相较于等高耕作措施,坡面径流削减率和泥沙削减率分别达到68.57%和94.29%;石坎反坡阶措施在提高坡面土壤水分含量、提高坡面水分分布均匀度方面能够发挥出良好的作用,该措施相较于等高耕作措施,坡面总体土壤水分含量提高了7.78%;石坎反坡阶措施能够显著提高坡耕地的农作物产量,相较于常规等高耕作措施,玉米产量提高了12.69%。石坎反坡阶的设计及作用效果研究,丰富了我国北方土石山区薄土坡耕地的水土流失治理途径。

薄土坡耕地石坎反坡水平阶水沙调控效果

为研究石坎反坡水平阶对于薄土坡耕地的水沙调控效果,设置了两个标准天然降雨径流小区(措施小区和对照小区)分别对次降雨径流和泥沙进行了观测,结果表明:石坎反坡水平阶措施能够有效地调控坡耕地地表径流,年均径流削减率为22.5%,且在短历时、大雨强降雨条件下的调控效果好于长历时、小雨强降雨;该措施对于坡耕地泥沙调控效果显著且稳定,年均泥沙削减率95.5%,措施小区的坡面产沙量随降雨特征值变化的波动幅度远远小于对照小区;石坎反坡水平阶措施通过减少坡面侵蚀,间接提高了坡耕地作物产量,春玉米年均增产6.2%。

新疆伊犁河流域沙质薄土层新垦耕地春小麦喷灌生产技术规程

伊犁河谷是新疆重要的商品粮生产基地,为了指导和规范新疆伊犁河流域沙质薄土层新垦耕地上从事春小麦种植生产的广大农户和团体,针对伊犁河流域水土开发区域面临沙质薄土层的灌溉问题和春小麦生产中存在的问题,依据国家、行业标准,在春小麦生产过程中科学合理地进行品种选择、培肥地力、平整土地、灌溉管理和配套栽培措施等进行了具体的规定,该生产技术规程的实施将实现春小麦生产的节水、节肥高效优质可持续发展,保证国家粮食安全,促进"西部大开发"战略实施和新疆农业结构战略调整布局。

工程改土对坡薄土性状影响的研究

采取野外观测与室内分析化验相结合的方法，对具有代表性的紫色坡薄地上实施的工程改立项目进行效益定位监测，结果表明，坡薄上水土流失受到抑制，水热矛盾日趋协调，土壤养分状况改善，“陡薄瘦蚀旱”得到缓解，收到了形质兼改的效果。

新疆伊犁河谷砂质薄层土新垦耕地棉花滴灌技术规程

伊犁河谷是重要的棉花生产基地,为了指导和规范新疆伊犁河流域砂质薄土层新垦耕地上从事棉花种植生产的广大农户和团场,针对伊犁河流域水土开发区域地面临砂质薄土层的灌溉问题及棉花生产中存在的问题。我们依据国家、行业标准,在棉花生产过程中科学合理地进行品种选择、培肥地力、平整土地、灌溉管理和配套栽培措施等进行了具体的规定。该生产技术规程的实施将实现棉花生产的节水、节肥高效优质可持续发展,保证了国家棉花产业安全,促进"西部大开发"战略实施和新疆棉花产业结构调整布局。

不同立地条件下山杏造林技术

近年国家在承德实施退耕还林、小流域治理、封山育林、防沙治沙等生态建设项目以来,山杏已被广泛用于营造水土保持林、防风固沙林、域区周围风景林等.但承德市区地处深山区,土壤瘠薄、立地条件差,水土保持能力差,加之近年连续干旱,致使造林成活率不足50%.针对此现象于2002～2003年在承德市区冯营子镇,根据不同的立地条件不同的季节,实施了不同的整地、栽植技术,其经验总结如下,供同类地区借鉴.

ANALYSES OF WAGNER'S MODEL

To achieve a better understanding of the effects of the colossal magnetoresistivity in the mixed valence manganites,the model of a negative magnetoresistivity scaling proposed by Wagner et al is explored in both mathematical and physical analyses.The inconsistency in Wagners model is discussed and corrected. The behaviors of the large spin polarons in Nd 0.52 Sr 0.48 MnO 3 film at T c are studied and analyzed.The results show that only through necessary corrections can Wagners model become self consistent. A further exploration of the nature of the magnetically aligned clusters will make the model more convincing.

天麻仿野生高效节材栽培技术

专词释疑:①仿野生。从数年来采挖的野生天麻中不难发现,个头大,生长密,产量高的天麻群体,有一个共同特点归纳为:腐叶层厚麻破地(露出地面),土壤疏松气不闭,林荫七分阳光少,四季水分各相宜。给予人工伤野生栽麻的启示是浅畦、薄土、厚盖(物)。②高效。仿野生天麻与红薯同畦套种。

Local Tensile Strength of Connection Between H-Steel Beam Flange and Concrete-Filled Circular Column Tube with Through Diaphragm

This paper focused on investigating local tensile strength of connection between steel beam flange and concrete-filled circular column tube with through diaphragm. Three specimens were designed and tested to failure, and the structure behavior was studied by experiment and FEM analysis. On the basis of the results obtained, an estimation for local plastic and ultimate strengths of the connections using yield line theory was attempted, which results in a good prediction.

Three-dimensional nonlinear analysis of creep in concrete filled steel tube columns

This paper proposes a based on 3D-VLE （three-dimensional nonlinear viscoelastic theory） three-parameters viscoelastic model for studying the time-dependent behaviour of concrete filled steel tube （CFT） columns. The method of 3D-VLE was developed to analyze the effects of concrete creep behavior on CFT structures. After the evaluation of the parameters in the proposed creep model, experimental measurements of two prestressed reinforced concrete beams were used to investigate the creep phenomenon of three CFT columns under long-term axial and eccentric load was investigated. The experimentally obtained time-dependent creep behaviour accorded well with the cu~＇es obtained from the proposed method. Many factors （such as ratio of long-term load to strength, slenderness ratio, steel ratio, and eccentricity ratio） were considered to obtain the regularity of influence of concrete creep on CFT structures. The analytical results can be consulted in the engineering practice and design.

Bearing mechanism and thickness optimization of ore roof in bauxite stope

Based on the elastic thin plate theory,the main law of the ore roof failure was analyzed and the formula of the ore roof thickness was deduced.The results show that the tensile stress in the roof center accounts for the roof failure.According to the limit failure conditions of the point,the formula of the ore roof thickness was derived.Taking No.10 stope of a bauxite mine as an engineering case,the optimal thickness of the ore roof was 0.36 m.The safety factor was taken as 1.3,therefore the design thickness was 0.5 m.In the whole industrial test process,the dynamic alarm devices did not start the alarm and the ore roof was not damaged.Compared with other stopes under similar conditions,its thickness was reduced by 0.1-0.3 m.The recovery rate of the ore roof was increased by 16.7%-37.5%.

Demolition technique of high thin-wall hyperbolic reinforced concrete cool tower by directional controlled blasting

Based on blasting demolition of high thin-wall hyperbolic reinforced concrete cool tower, by virtue of engineering practice of blasting the tube concrete structures, the analysis and research were made on the mechanism of cool tower collapse through selecting blasting parameters and selecting gap form, gap size and gap angle. The cool tower was twisted, collapsed directionally and broken well according to the design requirements. The expected results and purposes of blasting were obtained with no back blow, total blasted pile approximates to 4 - 5 m, no occurrence of flying stones and no damage to fixed buildings and equipment, the large-sized hyperbolic thin-wall reinforced concrete cool towers are twisted during blasting and it collapses well with good breaking. The test and measurement of blasting vibrating velocity was carried out during blasting and the measuring results are much less than critical values specified by Safety Regulations for Blasting. The study shows that gap form, gap size and gap angle are the key factors to cool tower collapse and will give beneficial references to related theoretical study and field application.

Influence of thinning on acidic deposition in Chinese fir plantations

Acidic deposition,which is mainly caused by atmospheric pollution,is one of the global environmental problems.Thinning is an effective management to improve the tree productivity,reduce the wildfire risk and maintain a healthy forest.Since thinning may reduce the effect of acidic deposition,the effect of thinning on acidic deposition was estimated.The biomass,soil properties,pH value of runoff and groundwater in both unthinned and thinned Chinese fir plantations were measured and compared over a 5-year period(2-6 years after thinning).The results indicated that acidic deposition in the Huitong State Ecosystem Research Station was serious,and it got worse with time.Forest thinning resulted in a huge change in biomass and soil properties.During the 5-year monitoring period,biomasses of understory and litter,plant species richness,coverage of undergrowth plant layer were significantly higher in thinned site than in unthinned site.Moreover,higher soil fertility as well as lower amounts of runoff and groundwater were found in thinned site.It was suggested that thinning could improve the structure of forest,leading to restoring the effluent(runoff and groundwater) pH to the normal value.

Design Guidelines for Buried Profile-Wall Pipe

The overall objective of this study was to provide guidance for proper design of profile-walled pipe. Data from buried pipe tests on HDPE pipes with thirteen different profiles were included in the study. These tests were run in the soil cell at Utah State University. Also, parallel plate tests were also completed on the pipe samples. Data from 39 buried pipe tests were analyzed. The buried tests were at 75, 85 and 95 percent of standard Proctor density. This paper summarizes the results of that study and focuses on the tests buried in 85 percent dense soil. In addition to the experimental data, a portion of this paper focuses on finite element analysis results to confirm and extend the results from the physical tests. Design limits are recommended for several dimensionless parameters that describe profile geometry. One of the significant conclusions of this study was that pipes with profiles that perform well when buried in soil also perform well in a parallel plate tests. The identities of the pipe manufacturers are not disclosed, and pipes are only described in terms of basic parameters such as cross-sectional area and area moments of inertia.

Seed and Fruiting Phenology Plasticity and Offspring Seed Germination Rate in Two Asteraceae Herbs Growing in Karst Soils with Varying Thickness and Water Availability

Shallow soil with low water availability is the key limiting factor for plant growth and reproduction in vulnerable karst regions.Annual herbs are pioneers adapted to these areas;however,little is known about the responses of their seeds and infructescence,and the germination of their offspring to these limited water and soil resources.In this study,we investigated how the seed and fruiting phenology plasticity and offspring seed germination rates of two annual Asteraceae herbs(Xanthium sibiricum and Bidens pilosa)respond to the harsh karst soil environment,by assessing the seed number,seed biomass and offspring seed germination rate.X.sibiricum and B.pilosa were grown under three soil thicknesses and three water availability levels in a full two-way randomized block design.The key results were as follows:(1)The number and biomass of progenies(infructescence and seeds)of X.sibiricum decreased with the decline of soil thickness and/or water availability(P<0.05).The infructescence and seed biomass of B.pilosa increased with the decline of water availability.(2)Seed quantity and seed biomass of X.sibiricum showed no correlation after their parents experienced resource reductions.A significant positive relationship between seed number and seed biomass was observed in B.pilosa(P<0.05).(3)The offspring seed germination rate of X.sibiricum did not change with the decrease of soil thickness under three levels of water treatment.However,the offspring seed germination rate of B.pilosa decreased significantly with the decrease of soil thickness under the control water level(P<0.05).The results show that X.sibiricum tends to improve its competitiveness by ensuring the quantity and quality of offspring in order to adapt to the shallow karst soils and dry karst habitats.In contrast,B.pilosa adapts to the unfavorable karst habitats by a risk-sharing strategy.B.pilosa produces more and bigger seeds to in an attempt to expand its survival range and escape from the unfavorable living environment,but this results in a lower seed number and germination rate of its progeny under the karst soil resource reduction.

Soil Phosphorus Distribution as Affected by Irrigation Methods in Plastic Film House

Water-saving irrigation methods have been increasingly used for vegetable cultivation in greenhouse or plastic film house. However, there is limited information concerning the effect of water-saving irrigation methods on soil phosphorus （P） behavior. In this experiment, drip and subsurface irrigation methods were applied, with furrow irrigation method as control, in Mollic Gleysols. Soil P distribution throughout the depth was significantly affected by irrigation methods. Total, Olsen, organic and inorganic P contents were greater in the topsoil （0-10 and 10-20 cm） than in the subsoil （20-30, 30-40, 40-50 and 50-60 cm）. The Olsen P content throughout 0-60 cm layer under drip and subsurface irrigation treatments was lower than that under the furrow irrigation treatment. However, the total, organic and inorganic P contents from 20 to 60 cm under drip irrigation treatment were higher than or close to those under furrow irrigation treatment, but were lower under subsurface irrigation treatment than under furrow irrigation treatment. Under subsurface irrigation treatment, the contents of total, organic and inorganic P at the 0-10 cm layer were 78.0%, 1.3% and 3.7% greater than those at the 10-20 cm layer, respectively. But Olsen P content at the 10-20 cm layer was 5.7% larger than that at the 0-10 cm layer. These suggested that soil P behavior could be manipulated by soil water management to some extent. 在