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| 1 | Analysis of soil moisture variation by forest cover structure in lower western Himalayas, India显示文摘Soil moisture affects various hydrological processes, including evapotranspiration, infiltration, and runoff. Forested areas in the lower western Himalaya in India constitute the headwater catchments for many hill streams and have experienced degradation in forest cover due to grazing, deforestation and other human activities. This change in forest cover is likely to alter the soil moisture regime and, consequently, flow regimes in streams. The effect of change in forest cover on soil moisture regimes of this dry region has not been studied through long term field observations. We monitored soil matric potentials in two small watersheds in the lower western Himalaya of India. The watersheds consisted of homogeneous land covers of moderately dense oak forest and moderately degraded mixed oak forest. Observations were recorded at three sites at three depths in each watershed at fortnightly intervals for a period of three years. The soil moisture contents derived from soil potential measurements were analyzed to understand the spatial, temporal and profile variations under the two structures of forest cover. The analysis revealed large variations in soil moisture storage at different sites and depths and also during different seasons in each watershed. Mean soil moisture storage during monsoon, winter and summer seasons was higher under dense forest than under degraded forest. Highest soil moisture content occurred at shallow soil profiles, decreasing with depth in both watersheds. A high positive correlation was found between tree density and soil moisture content. Mean soil moisture content over the entire study period was higher under dense forest than under degraded forest. This indicated a potential for soil water storage under well managed oak forest. Because soil water storage is vital for sustenance of low flows, attention is needed on the management of oak forests in the Himalayan region. | J. V. Tyagi Nuzhat Qazi S. P. Rai M. P. Singh | 2013 | Journal of Forestry Research2013，24，2： | 5 |
| 2 | Review of methods for predicting in situ volume change movementof expansive soil over time显示文摘The soil movement information over time is required for the design of foundations placed in expansive soils. This information is also helpful for the assessment of pre-wetting and controlled wetting mitigation alternatives for expansive soils. Several researchers during the past fifteen years have proposed different methods for the prediction of the soil movements over time. The available methods can be categorized into(i) consolidation theory-based methods,(ii) water content-based methods, and(iii) suction-based methods. In this paper, a state-of-the-art of the prediction methods is succinctly summarized. The methods are critically reviewed in terms of their predictive capacity along with their strengths and limitations. The review highlights the need for prediction methods that are conceptually simple yet efficient for use in conventional engineering practice for different types of expansive soils. | Hana H. Adem Sai K. Vanapalli | 2015 | 岩石力学与工程学报2015，34，1： | 3 |
| 3 | Effect of soil pore size distribution on plant-available water and least limiting water range as soil physical quality indicators显示文摘Soil pore size distribution(SPSD) is one of the most important soil physical properties. This research investigated the relationships of location and shape parameters of the SPSD curves with plant-available water(PAW) and least limiting water range(LLWR) of the light-textured soils at the Torogh Agricultural Research Station in north-eastern Iran. Soil moisture release curve(SMRC), PAW and LLWR in matric heads of 100 and 330 h Pa for the field capacity and location and shape parameters of the SPSD curves of 30 soils with different texture and organic carbon contents were determined, and the variable relationships were statistically analyzed. The results showed that the median equivalent pore diameter(de), mean de, standard deviation(SD*), and skewness of the SPSD curves were significantly correlated with PAW(PAW330) and LLWR(LLWR330) measured in a matric head of 330 h Pa. Decrease in deand increase in the diversity of soil pore size(SD*) increased PAW330 and LLWR330. The SD* values of all the soil samples were lower than the optimal ranges suggested in literature. Neither PAW nor LLWR values were significantly different in the soils with the optimal modal deand those with non-optimal modal de. Optimal values of median and mean equivalent pore diameters and kurtosis of SPSD curves led to a significant improvement of PAW330 and LLWR330 as soil physical quality indicators. It was recommended to revise the optimal ranges for SD* and modal defor future studies. | Mehdi ZANGIABADI Manoochehr GORJI Mehdi SHORAFA Saeed KHAVARI KHORASANI Saeed SAADAT | 2020 | Pedosphere2020，30，2： | 2 |
| 4 | Effects of Bentonite,Hydrogel and Biochar Amendments on Soil Hydraulic Properties from Saturation to Oven Dryness显示文摘Effects of hydrogel, bentonite, and biochar as soil amendments on soil hydraulic properties and improving water availability from saturation to oven dryness were investigated. Soils were mixed with hydrogel (0.10%, 0.25%, and 0.50%), bentonite (0.5%, 1.0%, and 2.5%), and biochar (1.0%, 2.5%, and 5.0%) as soil amendments (weight:weight). Three methods (extended multistep outflow (XMSO), evaporation (EVA), and WP4 dewpoint potentiometer) were used to measure soil hydraulic properties from saturation to oven dryness. The cumulative XMSO results were more uniform across all the applied pressure steps for the amended soils. The EVA exhibited a shorter linear decrease during the first evaporation stage and a lower evaporation rate during the second evaporation stage. The WP4 results also exhibited that soil amendments increased the soil water content of the amended soils at low matric potentials. The results of soil water retention curves revealed that the unamended soil retained less water at any matric potential compared to the amended soils. Soil hydraulic conductivity decreased with increasing amount of soil amendments. The saturated hydraulic conductivity was higher for the unamended soil than the soils amended w计h 2.5% bentonite, 0.50% hydrogel, and 5.0% biochar by 11, 3, and 18 times, respectively. These results suggested that soil amendments improved soil water retentivity, which confirmed the appropriateness of these soil amendments for potential use in sandy soil improvements. However, field experiments and economical perception studies should be considered for further investigation. | Osama M0HAWESH Wolfgang DURNER | 2019 | Pedosphere2019，29，5： | 2 |
| 5 | An approach to measure infill matric suction of irregular infilled rock joints under constant normal stiffness shearing显示文摘Rock joints infilled with sediments can strongly influence the strength of rock mass. As infilled joints often exist under unsaturated condition, this study investigated the influence of matric suction of infill on the overall joint shear strength. A novel technique that allows direct measurement of matric suction of infill using high capacity tensiometers(HCTs) during direct shear of infilled joints under constant normal stiffness(CNS) is described. The CNS apparatus was modified to accommodate the HCT and the procedure is explained in detail. Joint specimens were simulated by gypsum plaster using threedimensional(3D) printed surface moulds, and filled with kaolin and sand mixture prepared at different water contents. Shear behaviours of both planar infilled joints and rough joints having joint roughness coefficients(JRCs) of 8-10 and 18-20 with the ratios of infill thickness to asperity height(t/a)equal to 0.5 were investigated. Matric suction shows predominantly unimodal behaviour during shearing of both planar and rough joints, which is closely associated with the variation of unloading rate and volumetric changes of the infill material. As expected, two-peak behaviour was observed for the rough joints and both peaks increased with the increase of infill matric suction. The results suggest that the contribution of matric suction of infill on the joint peak normalised shear stress is relatively independent of the joint roughness. | Libin Gong Ana Heitor Buddhima Indraratna | 2018 | Journal of Rock Mechanics and Geotechnical Engineering2018，10，4： | 1 |
| 6 | The Principle of Interaction between Plastic Volumetric and Shear Strains for Unsaturated Soils显示文摘The principle of interaction between plastic volumetric and shear strains for rock and soil has been extended to the field of unsaturated soils.Two new interactions of suction-plastic volumetric strain and pore air pressure-plastic volumetric strain appear in the unsaturated state of a soil except the interaction between plastic volumetric and shear strains.It is very important to find that the suction possesses a dual property,which is the origin of generating its special functions.Thereby the effect of the suction on volumetric strain includes two opposite aspects.By means of this property of suction,the physical significance of effective stress parameter,effects of suction on volume change and preconsolidation pressure,and the mechanism of collapse upon wetting all can be explained.In addition,it is theoretically proved by application of this principle of interaction that the critical state line for unsaturated soils exists,and is unique and independent of the stress history. | Wang Jingtao1,2(1.Department of Architectural Engineering,Xinyang Normal University,Xinyang,Henan,464000,China 2.School of Civil Engineering and Mechanics,Huazhong University of Science and Technology,Wuhan,430074,China) | 2007 | 工程科学(英文版)2007，5，3： | 1 |
| 7 | Experimental investigation on cohesionless sandy bank failure resulting from water level rising显示文摘In the last decade, sediment replenishment forming cohesionless sandy banks below dams has become an increasingly common practice in Japan to compensate for sediment deficits downstream. The erosion process of the placed cohesionless sediment is a combination of lateral toe-erosion and the following mass failure. To explore cohesionless bank failure mechanisms, a series of experiments was done in a soil tank using a compacted sandy soil mass exposed to an increasing water level. Two types of uniform sand(D_(50) = 0.40 mm and 0.17 mm) and two bank heights(50 cm and 25 cm) were used under the condition of a constant bank slope of 75°. The three dimensional(3D) geometry of the bank after failure was measured using a handheld 3D scanner. The motion of bank failure was captured using the particle image velocimetry(PIV) technique, and the matric suction was measured by tensiometers. The compacted sandy soil was eroded by loss of matric suction accompanying the rise in water level which subsequently caused rotational slide and cantilever toppling failure due to destabilization of the bank. The effect of erosion protection resulting from the slumped blocks after these failures is discussed in the light of different failure mechanisms. Tensile strength is analyzed by inverse calculation of cantilever toppling failure events. The tensile strength had non-linear relation with degree of saturation and showed a peak.The findings of the study show that it is important to incorporate the non-linear relation of tensile strength into stability analysis of cantilever toppling failure and prediction of tension crack depth within unsaturated cohesionless banks. | Ryosuke Arai Kazuyuki Ota Takahiro Sato Yasushi Toyoda | 2018 | International Journal of Sediment Research2018，33，1： | 0 |
| 8 | Effects of Shallow Groundwater Table on Soil Matric Potential and Hydraulic Characteristics显示文摘Groundwater recharge significantly affects soil moisture redistribution through capillary rise. In this study,the soil matric potential at depths of 5, 10, 20 and 30 cm above the groundwater tables of 10, 30 and 60 cm weremeasured for 5 d. Soil hydraulic properties were analyzed by using the Philips and de Vries model. Results showedthat evaporation mainly influenced the matric potential of the shallow layer at the 5 cm depth regardless of the saturationof the layer. Groundwater recharge mainly affected soil moisture at the depth of 20 cm or more. A constant matricpotential layer existed between the evaporation front and capillary rise front where moisture content did not change.The isothermal-liquid hydraulic conductivity (KLh) and the thermal-vapor hydraulic conductivity (KvT) were thedominant hydraulic conductivities in the liquid and vapor phases. At the groundwater table depths of 10, 30 and 60 cm,the mean peak values of KLh were 2.32×10^-7, 1.63×10^-7 and 0.29×10^-7 m/s, respectively, whereas the mean peakvalues of KvT were 2.7×10^-7, 2.4×10^-7 and 1.8 ×10^-7m/s, respectively. | Jiang Jianmei Zhao Lin Qi Yun Zhai Zhe | 2014 | Transactions of Tianjin University2014，20，6： | 0 |
| 9 | THE MATRIC ALGORITHM OF LYAPUNOV EXPONENT FOR THE EXPERIMENTAL DATA OBTAINED IN DYNAMIC ANALYSIS显示文摘The Lyapunov exponent is important quantitative index for describing chaotic attractors. Since Wolf put up the trajectory algorithm to Lyapunov exponent in 1985, how to calculate the Lyapunov exponent with accuracy has become a very important question. Based on the theoretical algorithm of Zuo Binwu, the matric algorithm of Lyapunov exponent is given, and the results with the results of Wolf’s algorithm are compared. The calculating results validate that the matric algorithm has sufficient accuracy, and the relationship between the character of attractor and the value of Lyapunov exponent is studied in this paper. The corresponding conclusions are given in this paper. | 马军海 陈予恕 刘曾荣 | 1999 | Applied Mathematics and Mechanics(English Edition)1999，20，9： | 0 |
| 10 | The Stability of Unsaturated Soil Slope Affected by Rainfall Seeping显示文摘Because rainfall seeping makes losing stability of unsaturated soil slope, and arouses great loss to production and human being safety, the stability of unsaturated soil slope has been researched by many scholars recently. This article mainly uses the model for the prediction of shear strength with respect to soil suction, developed by Vanapalli and Fredlund to formulate rainfall seeping how to affect the stability of unsaturated soil slope. Firstly, volumetric water content of unsaturated soil slope changes with rainfall duration, and effective saturation changes with its volumetric water content. Secondly, soil volume weight changes with its volumetric water content. Thirdly, matric suction also changes with its volumetric water content. According to these causes, this article researches how much they make the contribution to the minimum safety coefficient respectively. At last, these factors roundly considered, this article gets the rule of minimum safety coefficient of unsaturated soil slope with rainfall duration that is minimum safety coefficient gradually increasing firstly, then decreasing that is composed of two sectors, first is slowly decreasing, then is fast decreasing after some value. | Zhang Shilin Wang Guochen Shao Longtan | 2007 | 工程科学(英文版)2007，5，1： | 0 |
| 11 | A DIRECT METHOD FOR THE UNIT CIRCLE PROBLEM显示文摘The unit circle problem is the problem of finding the number of eigenvalues of a non-Hermitian matrix inside and outside the unit circle . To reduce the cost of computing eigenvalues for the problem, a direct method, which is analogous to that given in [5], is proposed in this paper. | 卢琳璋 | 1994 | Numerical Mathematics A Journal of Chinese Universities(English Series)1994，3，1： | 0 |
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