Research on Test Method of Foundation Bed Coefficient in Nanjing Soft Soil Area

Relying on the geotechnical engineering survey project of Nanjing Lukou Airport, this research adopts the method of combining in situ and indoor testing to analyze the coefficient of soil foundation under different conditions (flow plastic, plastic, and soft plastic). Based on the differences in test results, in situ and indoor test methods appropriate for the benchmark bed coefficient of Nanjing soft soil area are proposed. Research findings depicted that the bed coefficients obtained by different methods are not similar; therefore, if the data obtained by different methods need to be compared and analyzed, they have to be unified as K 30 . Simultaneously, in the indoor test, this study compared the foundation bed coefficient obtained by the consolidation method, the improved K 0 instrument consolidation method, and the triaxial method. Results revealed that the improved K 0 instrument consolidation method can better realize the test of the soil foundation coefficient. This study can provide a reference for geotechnical investigation and design of soft soil in the study area.

Construction of Evaluation Model of Surface Soil Erodibility Factors in Black Soil Area

The increasing soil erosion in black soil area has caused widespread concern from all walks of life. Based on this background, the evaluation model of surface soil erodibility factor in black soil area is studied and constructed. The data of erosion gully is from the general survey data of surface soil erosion gully in black soil area. After quantifying the morphological characteristics of the data, the vector data of erosion gully are gridded by fractal theory. The number of non-empty grids is calculated by the attribute query function of ArcGIS, and the pixel size is transformed in turn to obtain different coverage grids and corresponding fractal parameters. The surface soil runoff and soil erosion process in black soil area are simulated by PESERA model. To build the surface soil erosion model of black soil area, in the process of building the user-defined model, it needs to carefully select the parameters used for modeling, and it needs to consider all the factors that may play a role in the whole process of soil erosion. The factors of surface soil erodibility in black soil area are analyzed, including spatial distribution characteristics of soil erodibility’s K value, semivariance function analysis of soil erodibility’s K value, and spatial distribution characteristics analysis of soil erodibility’s K value. Finally, the evaluation model of surface soil erodibility factor in black soil area is constructed. By testing the quantitative performance and evaluation accuracy of erodibility factors, it is proved that this method has good quantitative performance and evaluation accuracy of erodibility factors, and has strong practicability.

Aplikasi Dosis Vermikompos dan Urea Pada Tanaman Kedelai Varietas Anjasmoro di Tanah Berpasir

The low area for soybean plantation is still a major problem in meeting soybean needs. One of the efforts to increase national soybean production is by expanding the planting area by utilizing the sandy soil area that is still not used for soybean cultivation. This research was conducted from September-November 2020 in a greenhouse of the Agronomy Laboratory, Bengkulu University. This study aims to obtain the best dose of urea and vermicompost for the growth and yield of soybean in sandy soil. The research design used a completely randomized block design with two factors and 3 replications. The first factor was the dose of urea consisting of four levels, namely U0 = 0 kg ha-1, U1 = 50 kg ha-1, U2 = 100 kg ha-1, and U3 = 150 kg ha-1. The second factor was the dose of vermicompost, namely K0 = 0 ton ha-1, K1 = 5 tons ha-1, K2 = 10 ton ha-1, and K3 = 15 ton ha-1. The measured variables were the plant growth and the yield. Soil and vermicompost analyses were carried out before the study. The results showed that there was an interaction between the vermicompost and the urea dosages. The 100 kg ha-1 urea and the 10 ton ha-1 vermicompost treatment gave the highest plant height. The 150 kg ha-1 urea dan the 15 ton ha-1 vermicompost treatment formed the most number of branches. The highest soybean yield was given by 15 ton ha-1 vermicompost and 50 kg ha-1 urea to the total pod and the seed weight. Keywords: sandy soil, soybean, urea, vermicompost

Quality Assessment of Dry Soil Mixing Columns in Soft Soil Areas of Eastern China

To investigate the quality of dry soil mixing (DSM) columns in different soft soil areas of east China, a large number of laboratory test results and field test results of DSM columns were collected and analyzed statistically. Furthermore, a quality assessment method for DSM columns is proposed in this paper. The hardness description (HD), standard penetration test (SPT), unconfined compressive strength (UCS), and soil-cement column quality designation (SCQD) are used as assessment indexes. The statistical analysis showed that the test results of SPT, UCS, and SCQD were scattered, particularly in shallow ground. The mean values of the SPT blow count, UCS, and SCQD of the DSM columns decreased with depth: the greater the depth, the worse the quality of DSM columns. The quality assessment results showed that the proportion of the great quality columns was 64.84%, and the proportion of the unqualified columns was 1.4%. The proportion of DSM columns with great quality in the lagoon soft soil area was greater than in other areas. The proportion of unqualified columns in the lacustrine soft soil area was the largest. For all soft soil areas, the proportions of great quality, good quality, general quality, and unqualified soil decreased in that order. The quality assessment of 8627 DSM columns showed the proportions of great quality and unqualified were 64.84% and 1.4%, respectively. It was found that the greater the depth of the DSM column, the more unqualified DSM columns, and the more difficult it was to control the quality of DSM columns.

Birnbaum-Saunders Durability Life Prediction Model of Site-Exposed Concrete in the Saline Soil Area

Aiming at the prominent problem of short durability life of concrete in saline soil area and the shortcomings of indoor accelerated test, an outdoor field exposure test was designed. The concrete specimens were semiburied in the Tianshui area with salinized soil characteristics, and nondestructive testing was conducted every 180d (days). The durability evaluation parameters and mechanical performance indexes were selected for macroscopic analysis, and the corrosion mechanism was analyzed by using the SEM image and the XRD phase. The Birnbaum-Saunders model based on physical failure and probability statistics was used for life prediction. The results show that there are rod-shaped and chip-shaped crystals growing from the surface of the gel and the internal holes in the exposed end and the embedded end of the concrete. However, the damage and deterioration of the buried end are more serious than those of the exposed end. The corrosion products mainly included ettringite, gypsum, calcium carbonate, sodium sulfate hydrate, carbosilite, and Friedel’s salt. The reliability life curve based on the Birnbaum-Saunders model can describe the whole process of exposed concrete from damage accumulation to failure. In addition, the dynamic modulus degradation index is more sensitive to concrete durability damage, and the life obtained by the Birnbaum-Saunders model is shorter than the quality degradation index. The life obtained by this degradation index is taken as the life of the concrete exposed in the saline soil site, and the concrete life of C30, C40, and C50 is about 3340d, 3930d, and 4360d, respectively.

Influence of overliming vineyard acid soils on the macro-nutritional status of grapevines

Aim of study: The main aim of this study was to evaluate the effect of overliming with dolomitic lime on the topsoil and grapevine macro-nutritional levels (both petiole and grape tissues), as well as on berry weight and must quality properties in grapevines growing on an acid soil. Area of study: The study was carried out in the viticultural region of El Bierzo (Spain), one of the main wine protected designation of origin in the northwest of Spain. Material and methods: The effects of overliming were studied in soil parameters, petiole and grape tissues, as well as in must quality during three years (2014-2016). Data analysis was performed using factorial ANOVA (both parametric and non-parametric tests have been used). Main results: The results found on the soil levels of magnesium and phosphorus were mirrored by those shown in petiole and grape tissues. Data suggest that insufficient Mg supply in vineyard acid soils could lead to a lower P vascular movement in vines. Additionally, our findings suggest that a great decrease of K levels in vine tissues as a consequence of overliming, could lead to changes in harvest quality. Research highlights: Overliming with dolomitic limestone in large quantities decreased soil exchangeable K, as well as improved supply of exchangeable Mg and available P. Additionally Mg and P levels in both petiole and grape tissues were significantly affected by overliming.