Modeling of Hillslope Runoff and Soil Erosion at Rainfall Events Using Cellular Automata Approach

National Science Fund for Distinguished Young Scholars of China [40225004]; National Natural Science Foundation of China [40471048]

Numerical Analysis of Rainfall Infiltration in the Slope with a Fracture

With the finite volume method, a 2D numerical model for seepage in unsaturated soil has been established to study the rainfall infiltration in the fractured slope.The result shows that more rain may infiltrate into the slope due to existing fracture and then the pore pressure rises correspondingly. Very probably, it is one of the crucial factors accounting for slope failure. Furthermore a preliminary study has been conducted to investigate the influence of various fracture and rainfall factors such as the depth, width and location of a crack, surface condition, rainfall intensity and duration. Pore pressure and water volumetric content during the transient seepage are carefully examined to reveal the intrinsic mechanism.

Comparison of existing poroelastic models for wave damping in a porous seabed

Mechanism of wave-seabed interaction has been extensively studied by coastal geotechnical engineers in recent years. Numerous poro-elastic models have been proposed to investigate the mechanism of wave propagation on a seabed in the past. The existing poro-elastic models include drained model, consolidation model, Coulomb-damping model, and full dynamic model. However, to date, the difference between the existing models is unclear. In this paper, the fully dynamic poro-elastic model for the wave-seabed interaction will be derived first. Then, the existing models will be reduced from the proposed fully dynamic model. Based on the numerical comparisons, the applicable range of each model is also clarified for the engineering practice.

Modeling Nonlinear Peeling of Ductile Thin Films-Critical Assessment of Analytical Bending Models Using FE Simulations

Three analytical double-parameter criteria based on a bending model and a two-dimensional finite element analysis model are presented for the modeling of ductile thin film undergoing a nonlinear peeling process. The bending model is based on different governing parameters: (1) the interfacial fracture toughness and the separation strength, (2) the interfacial fracture toughness and the crack tip slope angle, and (3) the interfacial fracture toughness and the critical Mises effective strain of the delaminated thin film at the crack tip. Thin film nonlinear peeling under steady-state condition is solved with the different governing parameters. In addition, the peeling test problem is simulated by using the elastic-plastic finite element analysis model. A critical assessment of the three analytical bending models is made by comparison of the bending model solutions with the finite element analysis model solutions. Furthermore, through analyses and comparisons for solutions based on both the bending model and the finite element analysis model, some connections between the bending model and the finite element analysis model are developed. Moreover, in the present research, the effect of different selections for cohesive zone shape on the ductile film peeling solutions is discussed.

Designing Of Partial Similarity Models And Evaluation Method In Polymer Flooding Experiment

Based on the scaling criteria of polymer flooding reservoir obtained in our previous work in which the gravity and capillary forces, compressibility, non-Newtonian behavior, absorption, dispersion, and diffusion are considered, eight partial similarity models are designed. A new numerical approach of sensitivity analysis is suggested to quantify the dominance degree of relaxed dimensionless parameters for partial similarity model. The sensitivity factor quantifying the dominance degree of relaxed dimensionless parameter is defined. By solving the dimensionless governing equations including all dimensionless parameters, the sensitivity factor of each relaxed dimensionless parameter is calculated for each partial similarity model; thus, the dominance degree of the relaxed one is quantitatively determined. Based on the sensitivity analysis, the effect coefficient of partial similarity model is defined as the summation of product of sensitivity factor of relaxed dimensionless parameter and its relative relaxation quantity. The effect coefficient is used as a criterion to evaluate each partial similarity model. Then the partial similarity model with the smallest effect coefficient can be singled out to approximate to the prototype. Results show that the precision of partial similarity model is not only determined by the number of satisfied dimensionless parameters but also the relative relaxation quantity of the relaxed ones.

A new expression of hardening coefficients for fcc-crystal and calibration of the material constants

In order to describe the effect of latent hardening on the macro-plastic behavior of foc-crystal, a new expression for hardening coefficient is proposed in which there are 12 material constants, each having clear physical meaning. And a method of material constant calibration is suggested and used to determine the material constants of copper and aluminum crystal. The simulated load-elongation curves along various crystallographic orientations are comparable with the experimental ones.

Effects of rainfall infiltration on the stability of soil slopes

Slope failure due to rainfall is a common geotechnical problem. The mechanics of rainfall induced landslides involves the interaction of a number of complex hydrologic and geotechnical factors. This study attempts to identify the influence of some of these factors on the stability of soil slope including rainfall intensity, hydraulic conductivity and the strength parameters of soil.

Effects of rainfall infiltration on deep slope failure

With the finite element method and the limit equilibrium method, a numerical model has been estab-lished for examining the effects of rainfall infiltration on the stability of slopes. This model is able to reflect the variations in pore water pressure field in slopes, dead weight of the soil, and soil softening caused by rainfall infiltration. As a case study, an actual landslide located at the Nongji Jixiao in Chongqing was studied to analyze the effects of rainfall infiltration on the seepage field and slope sta-bility. The simulated results showed that a deep slope failure is prone to occur when rainfall infiltration leads to a remarkable variation in the seepage field, especially when the pore water pressure in slopes increases in a large range.

Construction of habitat suitability models (HSMs) for benthic macroinvertebrate and their applications to instream environmental flows: A case study in Xiangxi River of Three Gorges Reservior region, China

Based on a long-term ecological monitoring, the present study chose the most dominant benthic macroinvertebrate (Baetis spp.) as target organisms in Xiangxi River, built the habitat suitability models (HSMs) for water depth, current velocity and substrate, respectively, which is the first aquatic organisms model for habitat suitability in the Chinese Mainland with a long-term consecutive in situ measurement. In order to protect the biointegrity and function of the river ecosystem, the theory system of instream environmental flow should be categorized into three hierarchies, namely minimum required instream flow (hydrological level), minimum instream environmental flow (biospecies level), and optimum instream environmental flow (ecosystem level). These three hierarchies of instream environmental flow models were then constructed with the hydrological and weighted usable area (WUA) method. The results show that the minimum required instream flow of Xiangxi River calculated by the Tennant method (10% of the mean annual flow) was 0.615 m(3) s(-1); the minimum instream environmental flow accounted for 19.22% of the mean annual flow (namely 1.182 m(3) s(-1)), which was the damaged river channel. ow in the dry season; and 42.91% of the mean annual flow (namely 2.639 m(3) s(-1)) should be viewed as the optimum instream environmental flow in order to protect the health of the river ecosystem, maintain the instream biodiversity, and reduce the impact of small hydropower stations nearby the Xiangxi River. We recommend that the hydrological and biological methods can help establish better instream environmental. ow models and design best management practices for use in the small hydropower station project. (C) 2008 National Natural Science Foundation of China and Chinese Academy of Sciences. Published by Elsevier Limited and Science in China Press. All rights reserved.

Calibration of alkenone unsaturation index with growth temperature for a lacustrine species, Chrysotila lamellosa (Haptophyceae)

Although long chain alkenones (LCKs) occur widely in lacustrine sediments, their origin is not clear. Here, we report a lacustrine source, the non-calcifying species Chrysotila lamellosa Anand (Haptophyceae), collected and isolated from an inland saline water body, Lake Xiarinur (Inner Mongolia, China). Its alketione pattern is similar to those of coastal marine strains of C lamellosa,but the relationship between U-37(K') index and culture temperature for the lacustrine species is quite different from that of the coastal species. A significant feature of the alkenones in this strain of C lamellosa is a lack of C-38 methyl alkenones, which might be used to distinguish the species from the marine haptophyte species Emiliania huxleyi and Gephyrocapsa oceanica. The higher C-38 tetraunsaturated compound abundance might be another important feature for distinguishing the C lamellosa alkenone producer from the coastal species Isochrysis galbana. This alkenone distribution pattern has been detected in many lakes, which suggests that C lamellosa or a closely related species might be a very common alkenone precursor in lacustrine systems. We examined U-37(K') and U-37(K) values for C lamellosa as a function of culture temperature in a batch culture experiment. The calibration for U-37(K') vs. culture temperature (T) was U-37(K') = 0.0011 x T-2 - 0.0157 x T + 0.1057(n = 14, r(2) = 0.99) from 10 degrees C to 22 degrees C or U-37(K') = 0.0257 x T - 0.2608(n = 9, r(2) = 0.97) from 14 degrees C to 22 degrees C. U-37(K) vs. culture temperature was U-37(K) = 0 0377 x T - 0.5992(n = 14, r(2) = 0.98) from 10 degrees C to 22 degrees C. Our experiments show that the alkenone unsaturation index (U-37(K')) is strongly controlled by culture temperature and can be used for palaeoclimate reconstruction. (C) 2007 Elsevier Ltd. All rights reserved.

Calibration of microwave network analyzer

This paper presents a systematic description of the methods for calibrating microwave network analyzer and test fixtures, and discusses the problems arising in the calibration. The general criteria for choosing calibration standards and corresponding algorithms are discussed and suggestions to overcome these problems and improve the calibration accuracy are also given. It has been found that for reciprocal test fixtures, the four equations obtained with the thru standard can be used at the same time. Meanwhile, the calibration accuracy can be improved. It has been shown that using the same calibration procedures but different algorithms may lead to the occurrence of frequency limitation.

An improved TM method for full two-port calibration of the asymmetric test fixtures

Three known standards, including at least one transmission standard, are normally required for the full two-port calibration of test fixtures. Based on the triple-through method, a new general-purpose calibration procedure using only one known reflection standard is proposed in this paper. The experimental results show that our method call provide a simple and accurate approach to fall two-port calibration of the asymmetric test fixtures. (c) 2005 Wiley Periodicals, Inc.

Frequency limitation in the calibration of microwave test fixtures

The problem of frequency limitation arising from the calibration of asymmetric and symmetric test fixtures has been investigated. For asymmetric test fixtures, a new algorithm based on the thru-short-match (TSM) method is outlined. It is found that the conventional TSM method does not have any inherent frequency limitation, but using the same procedure with an unknown match may lead to the said problem. This limitation can be avoided by using a different algorithm. The various calibration methods for symmetric test fixtures using known standards are also discussed and the origin of the frequency limitation is identified. Several ways in avoiding the problem are proposed. There is good agreement between the theories and experimental data.

Two-port calibration of test fixtures with different test ports

The open-short-load (OSL) method is very simple and widely used for one-port test fixture calibration. In this paper, this method is extended, for the first time, to the two-port calibration of test fixtures with different test ports. The problem of phase uncertainty arising in this application has been solved. The comparison between our results and those obtained with the SOLT method shows that the method established is accurate for practical applications. (C) 2002 Wiley Periodicals, Inc.