Annual Discharge and Sediment Load Variation in Jialing River During the Past 50 Years

Annual discharge and annual suspended sediment loads of Beipei Hydrological Station of the Jialing River catchment were analyzed to describe the trend of Jialing River over the last five decades (1956-2006). These loads were also analyzed to ascertain the influential factors associated with its variation with the help of Kendall's Tau-b correlation analysis and regression analysis. The results indicated that the Jialing River annual discharge showed no significant trend at >95% confidence level while the annual sediment load appeared to have a significant decrease trend over the last 50 years. A decrease in the annual sediment load was particularly apparent after the year 1985, at which a substantial shift in the sediment level occurred. This shift is attributed to the construction of numerous dams in 1980s. However, after the year of 1985, two periodical stages (1986-1991 and 1992-2006) with distinct sediment load and sediment-runoff ratio were identified. The period 1992-2006 is characterised by low sediment load, which is most probably due to the impact of large scale of soil and water conservation, which took place at the end of the 1980s. Last, models describing the relationship between the discharge and the sediment load, discharge and sediment-runoff ratio as well as between the sediment load and sediment-runoff ratio were constructed.

An Ecologically Oriented Operation Strategy for a Multi-Reservoir System： A Case Study of the Middle and Lower Han River Basin, China

水库群的建设和调度改变了河流的自然流态,对河流生态系统造成了不利影响。本文提出了一种面向生态的水库群调度策略,将河流内不同生态功能所需的生态流量整合到水库群联合调度中,以实现生态流量需求和人类用水需求之间的均衡。该策略耦合了常规优化调度方案和一系列实时生态调度方案。在人类用水需求与生态流量需求冲突较小的时段,水库群调度在保障河流最小流量的前提下采用常规优化调度方案,最大限度地提高人类用水效益。在水库引发的水文改变对河流关键生态功能产生严重影响的时期,水库群调度采用实时生态调度方案,调整下泄流量,从而满足河流生态流量需求。该策略被应用于位于中国汉江中下游流域的一个大型水库群中。模拟调度结果表明,实时生态调度方案保证了河流关键生态功能的生态流量需求,其对人类用水效益的不利影响可通过常规优化调度方案得到部分补偿。本文提出的面向生态的水库群调度策略丰富了考虑生态流量需求的水库群联合调度的理论应用。

Effects of anti-pull ties on the bearing behaviors of shallow tunnel-type anchorages in soft rock

Tunnel-type anchorages(TTAs)installed in human gathering areas are characterized by a shallow burial depth,and in many instances,they utilize soft rock as the bearing stratum.However,the stability control measures and the principle of shallow TTAs in soft rock have not been fully studied.Hence,a structure suitable for improving the stability of shallow TTAs in soft rock strata,named the anti-pull tie(APT),was added to the floor of the back face.Physical tests and numerical models were established to study the influence of the APT on the load transfer of TTAs,the mechanical response of the surrounding rock,the stress distribution of the interface,and the failure model.The mechanical characteristics of APTs were also studied.The results show that the ultimate bearing capacity of TTAs with an APT is increased by approximately 11.8%,as compared to the TTAs without an APT.Also,the bearing capacity of TTAs increases approximately linearly with increasing height,width,length,and quantity of APTs,and decreases approximately linearly with increasing distance from the back face and slope angle of the tie slope.The normal squeezing between the tie slope and the surrounding rock increases the shear resistance of the interface and expands the range of the surrounding rock participating in bearing sharing.Both tension and compression zones exist in the APT during loading.The tension zone extends from the tie toe to the tie bottom along the tie slope.The range of the tie body tension zone constantly expands to the deep part of the APT with an increasing load.The peak tensile stress value is located at the tie toe.The distribution of compressive stress in the tie body is the largest at the tie top,followed by the tie slope,and then the tie bottom.

基于组件的三层式应用程序体系结构

针对目前客户 /服务器结构模式的不足 ,通过在其中引入中层形成了逻辑三层式体系结构 ,在此基础上给出了三层式体系结构的技术支持 ,重点探讨了三层式体系结构的实现问题。

坡面草被覆盖对坡沟侵蚀产沙过程的影响(英文)

By scouring experiments, the changeable process and characteristics of sediment yield in the hillslope-gully side erosion system with different coverage degrees and spatial locations of grass were studied. Five grass coverage degrees of 0, 30%, 50%, 70%, 90%, three spatial locations of grass （upslope, mid-slope, low-slope） and two water inflow rates of 3.2 L/min, 5.2 L/min were applied to a 0.5 by 7 m soil bed in scouring experiments. Results showed that the sediment yield decreased with the increase of grass coverage degree at 3.2 L/min water inflow rate in scouring experiments and the sediment yield with different grass locations on the sloping surface was in the order of upper 〉 middle 〉 lower. At 5.2 L/min water inflow rate, the differences of sediment yield among various grass coverage degrees were increased, whereas the changeable tendency of sediment yield with different grass locations on the whole sloping surface was not very obvious. The proportion of sediment yield from the gully side increased in an exponential relationship with the increase of grass coverage degree When the grass was located on the lower position of hillslope, the influence for accelerating gully erosion is the greatest.

Unsaturated expansive soil fissure characteristics combined with engineering behaviors

The relationship among the surface fissure ratio,moisture content,seepage coefficient and deformation modulus of field unsaturated expansive soil in Nanning,Guangxi Province,China,was obtained by a direct or indirect method.Digital images of expansive soil of the surface fissure with different moisture contents were analyzed with the binarization statistic method.In addition,the fissure fractal dimension was computed with a self-compiled program.Combined with in situ seepage and loading plate tests,the relationship among the surface fissure ratio,moisture content,seepage coefficient and deformation modulus was initially established.The surface fissure ratio and moisture content show a linear relation,"y=0.019 1x+1.028 5" for rufous expansive soil and "y=0.071x+2.610 5" for grey expansive soil.Soil initial seepage coefficient and surface fissure ratio show a power function relation,"y=1×10-9 exp(15.472x)" for rufous expansive soil and "y=5×10-7 exp(4.209 6x)" for grey expansive soil.Grey expansive soil deformation modulus and surface fissure ratio show a power function relation of "y=3.935 7exp(0.993 6x)".Based on the binarization and fractal dimension methods,the results show that the surface fissure statistics can depict the fissure distribution in the view of two dimensions.And the evolvement behaviors of permeability and the deformation modulus can indirectly describe the developing state of the fissure.The analysis reflects that the engineering behaviors of unsaturated expansive soil are objectively influenced by fissure.

An evaluation on using soil aggregate stability as the indicator of interrill erodibility

Aggregate stability is a very important predictor of soil structure and strength,which influences soil erodibility.Several aggregate stability indices were selected for estimating interrill erodibility of four soil types with contrasting properties from temperate and subtropical regions of China.This study was conducted to investigate how closely the soil interrill erodibility factor in the Water Erosion Prediction Project(WEPP) model relates to soil aggregate stability.The mass fractal dimension(FD),geometric mean diameter(GMD),mean weight diameter(MWD),and aggregate stability index(ASI) of soil aggregates were calculated.A rainfall simulator with a drainable flume(3.0 m long × 1.0 m wide × 0.5 m deep) was used at four slope gradients(5°,10°,15° and 20°),and four rainfall intensities(0.6,1.1,1.7 and 2.5 mm/min).Results indicated that the interrill erodibility(Ki) values were significantly correlated to the indices of ASI,MWD,GMD,and FD computed from the aggregate wet-sieve data.The Ki had a strong positive correlation with FD,as well as a strong negative correlation with ASI,GMD,and MWD.Soils with a higher aggregate stability and lower fractal dimension have smaller Ki values.Stable soils were characterized by a high percentage of large aggregates and the erodible soils by a high percentage of smaller aggregates.The correlation coefficients of Ki with ASI and GMD were greater than those with FDand MWD,implying that both the ASI and GMD may be better alternative parameters for empirically predicting the soil Ki factor.ASI and GMD are more reasonable in interrill soil erodibility estimation,compared with Ki calculation in original WEPP model equation.Results demonstrate the validation of soil aggregation characterization as an appropriate indicator of soil susceptibility to erosion in contrasting soil types in China.

Effects of liquefaction-induced large lateral ground deformation on pile foundations

The pile soil system interaction computational model in liquefaction-induced lateral spreading ground was established by the finite difference numerical method.Considering an elastic-plastic subgrade reaction method,numerical methods involving finite difference approach of pile in liquefaction-induced lateral spreading ground were derived and implemented into a finite difference program.Based on the monotonic loading tests on saturated sand after liquefaction,the liquefaction lateral deformation of the site where group piles are located was predicted.The effects of lateral ground deformation after liquefaction on a group of pile foundations were studied using the finite difference program mentioned above,and the failure mechanism of group piles in liquefaction-induced lateral spreading ground was obtained.The applicability of the program was preliminarily verified.The results show that the bending moments at the interfaces between liquefied and non-liquefied soil layers are larger than those at the pile’s top when the pile’s top is embedded.The value of the additional static bending moment is larger than the peak dynamic bending moment during the earthquake,so in the pile foundation design,more than the superstructure’s dynamics should be considered and the effect of lateral ground deformation on pile foundations cannot be neglected.

Evaluation and optimization of blasting approaches to reducing oversize boulders and toes in open-pit mine

A new blasting approach of combined blastholes with different diameters is proposed to solve the problems of oversize boulders and rock toes in open-pit mine. A non-ideal detonation model and a statistical damage constitutive model are implemented in dynamic finite element analysis to investigate the formation mechanism of oversize boulders and toes. The damage distribution and evolution process of rock blasting fragmentation is simulated, and the scheme is further optimized. Numerical analysis results showed that pocket charges and satellite blastholes can only improve bench top fragmentation, but they cannot reduce the oversize in the middle and bottom of bench as well as the toe problem. The new blasting approach of combined blastholes with different diameters can effectively reduce the oversize boulders and toes as well as the production costs.

Nitrogen Use Efficiency under Different Field Treatments on Maize Fields in Central China: A Lysimeter and ¹⁵N Study

Nitrogen loss from farmland has caused serious problems all over the world. This field study assessed Nitrogen Use Efficiency1 (NUE) and biomass yield under four different field treatments in the Hubei Province, in central China. Results show that 1) in these four treatments, the maize monoculture plots have the highest rate of fertilizer N losses (69.12%), and the lowest (32.45%) is treated by surface rice straw mulch of maize intercrop with peanut;2) compared with monoculture, polyculture plots have 36.9 kg·ha–1 and 26.57 kg·ha–1 more nitrogen absorption in the mulched and un-mulched plots respectively, however, polyculture has a lesser effect on NUE;3) surface straw mulch is an effective way to keep nitrogen in the soil (0 - 100 cm), however it may decrease dry matter yield in monoculture plots;4) maize intercrop with peanut and surface mulch can keep 47.63% of the fertilizer N in the soil profiles (0 - 100 cm), which is the highest among these four treatments.

An improved specimen preparation method for marine shallow gasbearing sand sediments and its validations

Instabilities of shallow gas-charged seabed are potential geological hazards in ocean engineering.In practice,the conventional field sampling techniques failed to obtain undisturbed gas-bearing sediments from the seabed for laboratory mechanical testing because of sensitive gas exsolution and escape from sediments.However,preparation of representative remoulded gas-charged specimens is a challenging issue,because it is rather difficult to quantitatively control the gas content and obtain uniform distribution of gas bubbles within the specimen.Given the above problems,this work proposes a reliable approach to reconstitute the high-saturation specimen of gas-charged sediments in the laboratory by an improved multifunction integrated triaxial apparatus(MITA).This apparatus is developed based on an advanced stress path triaxial system by introducing a temperature-controlled system and a wavemonitoring system.The temperature-controlled system is used to accurately mimic the in situ environments of sediments in the seabed.The wave-monitoring system is utilized to identify exsolution point of free gas and examine the disturbance of gas to specimens during gas exsolution.The detailed procedure of gassy specimen preparation is introduced.Then,the quality of prepared specimens using our improved apparatus is validated by the high-resolution micro-X-ray computed tomography(mCT)scanning test,from which bubble occurrence and size distribution within the gassy sand specimen can be obtained;and preliminary mechanical tests on gassy sand specimens with various initial saturation degrees are performed.The proposed specimen preparation procedure succeeds in proving the postulated occurrence state of gas bubbles in coarse-grained sediments and accurately controlling the gas content.

Post-liquefaction shearing behaviour of saturated gravelly soils: Experimental study and discrete element simulation

To investigate the post-liquefaction shearing behaviour of saturated gravelly soil,laboratory tests were conducted using a staticedynamic multi-purpose triaxial apparatus.In addition,numerical simulations using the discrete element method(DEM)were performed to preliminarily understand the micromechanism of gravelly soil in monotonic loading after liquefaction.The influences of dry density,initial confining stress and degree of liquefaction on the post-liquefaction shearing behaviour of gravelly soil were discussed,and the evolution of the micro-parameters of the granular system was also analysed.The results show that the stressestrain responses of gravelly soil after liquefaction can be divided into three stages:(1)low strength stage,(2)super-linear strength recovery stage,and(3)sublinear strength recovery stage,which are distinctly different from those of the general saturated gravelly soil without previous cyclic loading.The initial state and prior dynamic stress history have significant influences on the post-liquefaction shearing behaviour of gravelly soil.The DEM simulation revealed that the average coordination number sharply increases,the contact normal shows an obvious orientation distribution,and the destroyed force chain backbones are reconstructed in the monotonic reloading process after liquefaction.The evolution of the micro-parameters of the granular system clearly reflects the interior interaction process and micro-mechanisms in the particles during the three different stages of the macro-mechanical behaviour of gravelly soil.

Fuzzy stochastic generalized reliability studies on embankment systems based on first-order approximation theorem

In order to address the complex uncertainties caused by interfacing between the fuzziness and randomness of the safety problem for embankment engineering projects, and to evaluate the safety of embankment engineering projects more scientifically and reasonably, this study presents the fuzzy logic modeling of the stochastic finite element method （SFEM） based on the harmonious finite element （HFE） technique using a first-order approximation theorem. Fuzzy mathematical models of safety repertories were introduced into the SFEM to analyze the stability of embankments and foundations in order to describe the fuzzy failure procedure for the random safety performance function. The fuzzy models were developed with membership functions with half depressed gamma distribution, half depressed normal distribution, and half depressed echelon distribution. The fuzzy stochastic mathematical algorithm was used to comprehensively study the local failure mechanism of the main embankment section near Jingnan in the Yangtze River in terms of numerical analysis for the probability integration of reliability on the random field affected by three fuzzy factors. The result shows that the middle region of the embankment is the principal zone of concentrated failure due to local fractures. There is also some local shear failure on the embankment crust. This study provides a referential method for solving complex multi-uncertainty problems in engineering safety analysis.

Numerical simulation for rheological characteristics of alternating distribution of soft and hard rock layers

The difficulty of selecting appropriate rheological model and parameters for the alternating distribution of soft and hard rock layers was often encountered due to the unhomogeneity, discontinuity and anisotropy of rock mass. The Burgers and generalized Kelvin models were applied to the soft and hard rock respectively and the rheological parameters were obtained based on the method of optimum separation. By using the simulated code FLAC^(3D), the stability of surrounding rocks of a certain underground plant was analyzed. The effect of surface load and weakening the parameters intensity of argillaceous and bioclastic interlayers between soft and hard rock on rheological behavior of layer composite rock mass was investigated. The results indicate that the rheological characteristics of soft and hard rock layer in composite rock mass can be described well with above two rheological models.

Macro mechanical parameters’ size effect of surrounding rock of Shuibuya project’s underground power station

Scale effect is one of the important aspects in the macro mechanical parame- ters’ research of rock mass, from a new point of view, by means of lab and field rock me- chanics test, establishment of E^Vp relation, classification of engineering rock mass, nu- merical simulation test and back analysis based on surrounding rock’s displacement monitoring results of Shuibuya Project’s underground power station, rock mass deforma- tion module’s size effect of surrounding rock of Shuibuya Project’s undegroud power sta- tion was studied. It’s shown that rock mass deformation module’s scale effect of sur- rounding rock of Shuibuya Project’s undeground power station is obvious, the rock mass deformation module to tranquilization is 20% of intact rock’s. Finally the relation between rock mass deformation modules and the scale of research was established.

Outdoor Aging Performance of HDPE Geogrid

An outdoor aging test base for geosynthetics was established in Wuhan,central China to investigate the long-term aging performance of geosynthetics. Outdoor photo-oxygen aging tests for high density polyethylene(HDPE) geogrid have been carried out in the base. Test results show that in the initial nine months,the tensile strength of geogrid remains unchanged or even gets larger,while the corresponding strain at break decreases slightly,exhibiting hard and brittle trend due to secondary compensatory responses to the ultraviolet(UV) aging: UV provides the required chemical crosslinking energy,resulting in the polymer crosslinking reaction. Tensile strength of the geogrid increases by about 5% in the initial nine months,but decreases after the initial nine months. The long-term research results at the test base could provide first-hand data for researching the aging properties of HDPE geogrid.

陕西商南县栓皮栎林分评价与管理(英文)

The present study was conducted within the frame of the Sino-German project "Rehabilitation of degraded land ecosystems in the mountainous area of the Southern Shaanxi Province,China".The study deals with the assessment of the potential of oak coppices as well as the evaluation of the socioeconomic conditions in the Shangnan County.The ultimate objective of the study is to provide recommendations on the sustainable management of forest resources,which does not only aim to improve the environmental situation but also to satisfy the demands of the local rural residents.The study was based on 30 samples of oak coppices stands,which were randomly selected within an area of a size of 20 km × 20 km.In each selected stand,the mature stand and understory regeneration were investigated in depth.For the socio-economic survey,175 households from 11 villages were randomly selected.Results revealed that the stocking capacity of the cork oak coppices reaches 120 m3/ha in average at the older age classes(≥25 years) even after frequent timber harvest.High potential for productivity was indicated by the availability of sufficient vigorous individuals at different age classes.In addition,the understory regeneration was sufficient in density(19,000±133 individual/ha) and consisted of diverse valuable native-species(17 species within a survey area of 400 m2).The results of the assessment of the oak coppices provided possibilities for some practices that can be recommended towards sustainable management of such stands.On the other hand,results of the socioeconomic study showed a high degree of acceptance among the local inhabitants(79% of the total households) to change traditional land use,providing an enhancement of their economic situation.

Texture Image Segmentation Based on Nonlinear Diffusion

质地图像分割基于非线性的散开被介绍。质地的规模能在非线性的散开的过程期间被测量。有保存的边的一幅光滑的 5 隧道向量图象，紧张镇静，可伸缩，质地的取向想象，能被联合非线性的散开完成。一个多信道的统计区域活跃轮廓被采用分割这幅向量图象。因为参数不对不同质地图象敏感，方法能被看作一种无指导的分割。试验性的结果在质地图象的半自动的抽取显示出它的高效率。

Introduction to rainwater management in Australia and suggestions for China's water problems

Australia is one of the world leaders in water management. The country meets the challenge of water shortage with established integrated water management in which rainwater is taken as a too precious resource to be just drained off. In Australia, rainwater is extensively harvested and polished to provide cheaper supply for potable and non-potable domestic uses, irrigation, landscaping, refilling aquifers and other uses. Implementing dual management over the quantity and quality of storm water and practicing water sensitive urban design (WSUD) in urban areas effectively control non-point-source pollution of waterways by pollutants carried with runoffs, reduce the discharge of rainwater and thus protect properties and lives from damage by floods. These achievements are attributed to constant reinforcement by govenments from federal to local levels in policy, financial, legal and educational aspects, and also to the lasting efforts of professional communities and water industry in developing requisite techniques, demonstrating the benefits and fostering public credence of rainwater reuse. The successful rainwater management practices in Australia suggest rainwater harvesting can be a complimentary means for the South-to-North Water Transfer Scheme to solve the water shortage in China's northern regions, and thus release to a degree the pressure on the Yangtze water resources. Best management practices of rainwater can be an effective controlling strategy for flooding and non-point-source water pollution of waterways. Such in-site source control initiatives have particular significance to protecting slow waterways of weak self-purification ability, like the Three Gorges Reservior.