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Lily bulb is an underground tuber crop, which is mainly grown in southern China. At present, lily bulb harvesting mainly adopts manual excavation, resulting in low labor efficiency. Coupled with the high soil viscosity in lily bulb planting area, there are some problems in lily bulb mechanized harvesting, such as difficulty in fruit-soil separation and high damage rate of lily bulb. In order to solve the problems of poor separation effect, high rate of buried fruit and high crushing rate during lily bulb harvest in sticky soil, a kind of throwing roller lily bulb harvester suitable for operation in sticky soil was designed. The throwing roller lily bulb harvester is composed of vibration conveying device, throwing roller set, excavating shovel and other parts. It has the functions of vibrating crushing soil, throwing crushing soil and material conveying. It can effectively realize the secondary crushing of clay soil, and the separation effect of fruit-soil is good and does not hurt lily bulb, which is very suitable for the mechanical harvesting of lily bulb under the condition of clay soil. Combined with the growth condition of lily bulb and the requirements of planting agriculture, the motion process and separation mechanism of fruit and soil mixture on the vibration conveying device and the throwing roller set were analyzed, the dynamic model of throwing and colliding crushed soil on the throwing roller was established, and the relationship between the structure size of the throwing roller and the crushing of the clay-heavy soil block was established. Through the analysis, the structure and maximum swing Angle of the vibration conveying device, the series of throwing roll sets, the number of throwing roll teeth, the diameter of throwing roll and the contour size and other parameters were obtained. Through theoretical analysis and calculation, the structural parameters of vibration conveying device and throwing roller set of key components were determined. The length of vibration grating rod of vibration conveying device was 150mm, the distance between vibration grating rod was 50 mm, and the swing Angle of vibration grating rod was 59.12°. The number of teeth of the throwing roller wheel was 4 teeth. The radius of the throwing roller wheel was 250 mm. The spacing of the throwing roller wheel was 50 mm. According to the designed structural parameters, a prototype was built and the multi-factor test of operation parameters was carried out. The forward speed of the fruit-soil separation mechanism, the rotation speed of the throwing roller and the digging depth were taken as the test factors, and the embedding rate and crushing rate of lily bulb were taken as the test indicators. Box-Benhnken test method was used to establish the regression equation of factors and test indicators and the influence law of factors on lily bulb harvest index was obtained. When the optimum parameter combination was 0.6 m/s, 90 r/min and 170 mm, the field test values of the rate of buried fruit and the rate of broken lily bulb were 6.3% and 7.1%, respectively. The performance of the machine met the design requirements. The research results can provide reference for the research of mechanization harvesting technology and equipment of lily bulb. [ABSTRACT FROM AUTHOR]

Soft marine deposits are widely distributed in the coastal region of China. The marine soft clays have high water content and high sensitivity, which shows high compressibility and low strength. The installation of precast piles for wind turbines over soft marine clay will generate high excess pore water pressure (EPWP) with very low dissipation rate, resulting in low bearing capacity and large postconstruction settlement, which will affect long-term stability. This study investigated the generation and dissipation of the EPWP correlated with the change in soil structure during the installation of pile foundations in a project of 100 MW wind-power generation in Lianyungang, Jiangsu, China. The results show that the marine soft clay soils feature strong natural structures based on the intrinsic compression concept. The EPWP decreases with increasing distance from the pile, whose influence reaches a distance of 6 m (about 10 times the pile side length). The structural strength of natural sedimentary clay has a remarkable impact on the generated EPWP. The dissipation rate of the EPWP is very slow in mucky clay with more than half the residual value after 30 days, which is mainly attributed to the sharp decline of consolidation coefficient induced by the disturbance of natural clay soils from pile driving. Moreover, hydraulic fracturing can well explain the dissipation characteristics of the EPWP in clay. This phenomenon is actually an ongoing process especially in marine soft clay soils with a strong cementation effect. [ABSTRACT FROM AUTHOR]

Visible and near‐infrared reflectance (Vis‐NIR) spectroscopy is considered a promising tool for the estimation of soil properties. Soil clay content and soil organic matter (SOM) are main components affecting soil spectra. Accurate assessment of clay content and SOM is essential before achieving accurate prediction for other soil properties. Selecting the proper spectral transformation technique and optimal calibration method are important processes to improve model performance. In this study, a total of 240 soil samples were collected from the main area of winter wheat (Triticum aestivum L.) fields in the Southwest region of Shanxi province, northern China. Six spectral pre‐treatments and three multivariate methods were utilized to realize the estimation of clay content and SOM. Finally, the important spectral wavelengths were identified as 440, 762, 1,150, 1,410, 1,460, 1,860, 1,900, 2,250, 2,400 nm for clay content and 410, 450, 550, 625, 780, 850, 1,410, 1,670, 1,730, 1,860, 1,910, 1,960, 2,250 nm for SOM. Specifically, the wavelengths around 440 (450), 1,900 (1,910) nm and wavebands of 1,410, 1,860, and 2,250 nm were highly related to both clay content and SOM. The optimal prediction was obtained when multiple linear regression (MLR) was combined with standard normal variate (SNV) pre‐processing (R2 =.714, RMSE = 3.982, RPD = 1.584) for clay content and multiplicative scatter correction (MSC) pre‐processing (R2 =.856, RMSE = 2.994, RPD = 2.443) for SOM. This study implied that spectral transformation had an evident effect on spectral curves shape, correlation, and model performance. The choice of pre‐processing transformation should depend on the multivariate technique which has a determined ability to improve the model accuracy. Core Ideas: Determining the important spectral wavelengths for soil clay and soil organic matter.Realizing the robust estimation on soil clay and soil organic matter by using spectral technology.Exploring the approaches to improve predictive accuracy of soil clay and soil organic matter models. [ABSTRACT FROM AUTHOR]

In the design of reclamation, long-term settlement is seriously concerned. This paper presents a case study on the ground settlement of a reclamation project in Nansha, China. Fourteen undisturbed soil samples were taken at different depths from this site. Both oedometer tests on fourteen specimens and triaxial hydraulic conductivity tests on nine specimens were conducted. Finite element (FE) modelings using soft soil creep (SSC) model or soft soil (SS) model for modeling clayey soils with or without creep and the calculation using a new simplified method were performed to analyze the consolidation settlement of clay deposits subjected to filled loadings. The FE simulated results and calculated results from the new simplified method were compared with the monitored data in the field. Results show that the curves of the FE modeling using SSC model and the calculation from new simplified method have the same trends as those of the measured settlements. The creep contributes to excess pore pressure dissipation during the consolidation. Furthermore, ground settlements of the reclamation are predicted with the aid of the FE and new simplified method analysis. These predictions can provide the essential information for engineers to control or reduce the settlement in future. [ABSTRACT FROM AUTHOR]

Conventionally, red clay is used for agricultural purposes in southern China. Fertilizers, especially urea, are commonly introduced into the red clay to improve the crop yields. However, due to the rapid urbanization in China, large areas of lands with red clays have been converted into sites for domestic and industrial constructions. Nevertheless, few researchers focused on the effect of urea on the strength and compressibility of red clay. In this research, the shear strength and compressibility of the red clay saturated by different concentrations of the (NH4)2CO3 solution (urea's hydrolysates) were experimentally investigated using direct shear as well as oedometer tests, respectively. It was noticed that both the shear strength and stiffness of the red clay significantly decreased after exposure to the urea solution. In addition, the micromechanisms of the strength and compressibility of the red clay treated by the (NH4)2CO3 were studied by the scanning electron microscope test and X‐ray diffraction test. Based on the test results, a new model was developed to simulate the chemomechanical behavior of saturated clayey soil by modifying the Barcelona basic model (BBM) for unsaturated soils. The proposed model introduces four additional parameters, compared to the BBM, to account for the nonlinear shear strength behavior of the red clay. This model accounts for most of the complex features related to the strength and stiffness behavior of clayey soils. The parameter calibration procedures, by using the oedometer and direct shear test results, are also presented. To validate the proposed model, experimental results from the literature are considered in which illite clay samples were either mechanically or chemically or both mechanically and chemically loaded. Part of the experimental results is used to calibrate the model parameters and the other part along with the calibrated parameters is used to verify the proposed model. A comparison between experimental data and predicted results demonstrated that the proposed model is able to capture the main features related to the chemomechanical coupling behavior of saturated soils. [ABSTRACT FROM AUTHOR]

Earth pressure balance shield (EPBS) has become the mainstream construction method for metro tunnels in China, which inevitably generates a large amount of discharged soil, putting enormous pressure on the environment and the cost. In order to realize the resource utilization of shield dregs, this paper explored the feasibility of recycling the waste silty clay as a soil conditioner in EPBS tunnel construction. Mixtures of bentonite, wasted silty clay, carboxymethyl cellulose (CMC), and tap water in different ratios were prepared. Defining the substituted ratio as the mass ratio of silty clay to (bentonite + silty clay), the effect of the substituted ratio on the apparent viscosity, flow curve, rheological model and physical stability of bentonite-silty clay composite slurry were investigated. Furthermore, the relationship between slurry microstructures and macroscopic rheological properties was revealed by scanning electron microscopy (SEM). The results show that the constitutive relationship of bentonite slurry (0% substituted ratio) can be well described by Herschel-Bulkley model. The silty clay has a deteriorating effect on the rheological behavior and physical stability, and changes the flow pattern of the composite slurry. Microscopically, CMC makes the clay particles in slurries form agglomerates with larger particle sizes, and can absorb excess free water from the slurry, thus significantly increasing the yield stress and apparent viscosity. The recycling scheme proposed in this study can not only greatly reduce the procurement cost of raw materials, but also eliminate the transportation and disposal costs of discharged soil, which has significant environmental benefits and promising application prospects. [ABSTRACT FROM AUTHOR]

The evolution of sliding zone soil originating from a muddy interlayer in the Three Gorges Reservoir (TGR) in China is accompanied by an increase in clay content, and the subsequent changes in its mechanical properties control the initiation or reactivation of large-scale bedrock landslides. In this paper, using sliding zone soil samples from the Xingfusi landslide in the Wanzhou area, two groups of remolded saturated specimens were prepared with clay contents of 25.0% and 12.5%. Direct shear creep tests and a series of ring shear tests were carried out to investigate the shear behaviors of the specimens with different clay contents. On this basis, the effect of clay content on the evolution of landslides was discussed. The results show that (1) during the long-term creep process before landslide initiation, the shear creep modulus of sliding zone soil in steady creep state significantly decreases with an increase in clay content, which results in the increase in cumulative creep displacement. (2) The increase in clay content in sliding zone soil will lead to a reduction in peak shear strength and residual frictional resistance. In the drained shearing on saturated sliding zone soil with a high clay content, the excess pore-water pressure on the sliding surface cannot dissipate as rapidly due to the small permeability of sliding zone soil with a high clay content, which may favor postfailure movement. (3) With an increase in shear displacement rate, the residual strength first shows a weak "negative shear rate effect" and then shows a significant "positive shear rate effect". However, with an increase in clay content, the initial shear rate for the residual strength showing a "positive rate effect" will decrease. (4) Sliding zone soil with a high clay content generally does not exhibit strength recovery, while sliding zone soil with a low clay content clearly recovers its peak residual strength due to volume change of the shear zone caused by secondary compression after a long period of reconsolidation. In this case, a greater external load or reduction in effective normal stress needs to be applied to reactivate the landslide. • An increase in clay content of sliding zone soil results in the increase in cumulative creep displacement. • High clay content decreases the initial shear rate for the residual strength showing a "positive rate effect". • The effect of clay content on the strength recovery of sliding zone soil was revealed. • The effect of clay content on the whole evolution of landslides was explained. [ABSTRACT FROM AUTHOR]

Taiyuan city has experienced serious land subsidence since the 1950s, with the maximum accumulated subsidence of 2,960 mm and a total affected area of 585 km2 by 2003. Tectonic settlement was found to contribute about 1% and the major cause is over-exploitation of groundwater. The spatial–temporal relationship between the areal distribution of land subsidence and that of groundwater drawdown from 1956 to 2000 indicates that although land subsidence centers overall match groundwater depression cones, there are local deviations, and that although the time series curves are similar, land subsidence always lags behind groundwater level decline, with different lag time at different sites. The major findings of this work on the control of stratigraphic heterogeneity on the spatial pattern of land subsidence at Taiyuan include: (1) land subsidence centers shift from the corresponding groundwater depression cones to the sides with thicker accumulated clay layers; (2) under the same pumping rate, land subsidence at places with more clay interlayers and thinner individual interlayers is greater and the lag time shorter; and (3) land subsidence is closely related to the physical properties of clay soils. The Interbed Storage Package-1, a modular subroutine of MODFLOW was employed to simulate the areal distribution of individual layer compression. The modeling results show that compression of different clay layers has different contribution to land subsidence. Pumping groundwater from water-bearing zones close to the most compressible clay layers should therefore be carefully controlled. [ABSTRACT FROM AUTHOR]