RESUMO
With the economic development, a large number of engineering accumulation bodies with Lou soil as the main soil type were produced in Guanzhong area, Northwest China. We examined the characteristics of runoff and sediment yield of Lou soil accumulation bodies with earth (gravel content 0%) and earth-rock (gravel content 30%) under different rainfall intensities (1.0, 1.5, 2.0, 2.5 mm·min-1) and different slope lengths (3, 5, 6.5, 12 m) by the simulating rainfall method. The results showed that runoff rate was relatively stable when rainfall intensity was 1.0-1.5 mm·min-1, while runoff rate fluctuated obviously when rainfall intensity was 2.0-2.5 mm·min-1. The average runoff rate varied significantly across different rainfall intensities on the same slopes, and the difference of average runoff rate of the two slopes was significantly increased with rainfall intensity. Under the same rainfall intensity, the difference in runoff rate between the slope lengths of the earth-rock slope was more obvious than that of the earth slope. When the slope length was 3-6.5 m, flow velocity increased rapidly at first and then increased slowly or tended to be stable. When the slope length was 12 m, flow velocity increased significantly. In general, with the increases of rainfall intensity, inhibition effect of gravel on the average flow velocity was enhanced. When rainfall intensity was 2.5 mm·min-1, the maximum reduction in the average flow velocity of earth-rock slope was 61.5% lower than that of earth slope. When rainfall intensity was less than 2.0 mm·min-1, sediment yield rate showed a trend of gradual decline or stable change, while that under the other rainfall intensities showed a trend of rapid decline and then fluctuated sharply. The greater the rainfall intensity, the more obvious the fluctuation. There was a significant positive correlation between the average sediment yield rate and runoff parameters, with the runoff rate showing the best fitting effect. Among the factors, slope length had the highest contribution to runoff velocity and rainfall erosion, which was 51.8% and 35.5%, respectively. This study can provide scientific basis for soil and water erosion control of engineering accumulation in Lou soil areas.
Assuntos
Sedimentos Geológicos , Chuva , Solo , Movimentos da Água , China , Solo/química , Ecossistema , Monitoramento Ambiental/métodos , Gravitação , EngenhariaRESUMO
To investigate the effects of gravel content on runoff and sediment yield on Lou soil accumulation slopes, we conducted indoor simulation rainfall experiments and examined the characteristics of runoff and sediment yield on accumulation slopes with five gravel contents (10%, 20%, 30%, 40%, 50%) under four rainfall intensities (1.0, 1.5, 2.0, 2.5 mm·min-1), with a no gravels slope as control. The average runoff rate under different test conditions ranged from 2.18 to 13.07 L·min-1. The average runoff rate was the maximum under the gravel content of 10% (or 20%) and the minimum under the 50% gravel content. The average flow velocity ranged from 0.06 to 0.22 m·s-1. The variation of flow velocity was complex. The smaller the gravel content, the larger the range of variation and the coefficient of variation. The average flow velocity reached the maximum when the gravel content was 10%. The presence of gravel effectively inhibited the sediment yield, and the sediment reduction benefit reached 84.2%. The rainfall intensity had more influence on the average sediment yield rate than gravel content. Results of partial correlation analysis showed that gravel content was significantly negatively correlated with the ave-rage runoff rate, the average flow velocity, and the average sediment yield rate. The relationships between the ave-rage sediment yield and the average runoff rate, the average flow velocity, and their interaction were all extremely significant linear functions, with the strongest relationship between the average sediment yield and the average runoff rate. This study could provide references for the control of soil erosion and the establishment of erosion models for engineering accumulations in Lou soil areas.
Assuntos
Solo , Movimentos da Água , Chuva , Receptor para Produtos Finais de Glicação Avançada , Sedimentos GeológicosRESUMO
Vegetation restoration in the Chinese Loess Plateau has significantly changed soil erosion process of gully head wall. In order to investigate the characteristics and controlling factors of soil anti-scour properties of gully head covered by grasses, we carried out indoor undamaged soil trench scouring tests. By using barren gully head as the control, the physical and chemical properties and anti-scouring characteristics of soil in different soil layers (0-10, 10-20, 20-40, 40-60, 60-80, 80-100 cm) of the vertical wall of gully with grass cover were analyzed. The results showed that water-stable aggregate content and cohesion in barren and grass-covering gully head decreased with soil depth. Soil organic matter content and soil anti-scouribility coefficient in barren gully head decreased with soil depth, while the two indicators for gully head covered by grass increased firstly and then decreased with soil depth, with the maximum value (24.30 g·kg-1 and 58.86 L·g-1) in 10-20 cm soil layer. Meanwhile, the soil anti-scouring coefficient in each soil layer of grass-covering gully head was 1.7-9.3 times of that in soil layer of barren gully head. Soil organic matter content, water-stable aggregate content, cohesion and root length density all presented significantly positive correlation with soil anti-scouribility, among which soil organic matter content had the highest coefficient (r=0.98). Results of this study might provide basic data for the study of headcut erosion mechanism in Loess Plateau gully region, and scientific basis for effective control of soil and water loss in this region.
Assuntos
Poaceae , Solo , China , Solo/química , ÁguaRESUMO
The engineering deposits produced by the increasing frequency of production and construction activities are the main source of man-made soil erosion. In this study, we examined the change of runoff-sediment relationship and erosion hydrodynamic characteristics with the engineering deposits of aeolian sandy soil and red soil, based on simulated rainfall experiments with different gravel contents (0, 10%, 20%, 30%) and rainfall intensities (1.0, 1.5, 2.0, 2.5 mm·min-1). The results showed that the sediment yield rate of the aeolian sandy soil deposits gradually increased with the duration of rainfall. The sediment yield rate of red soil deposits under 1.0 mm·min-1 rainfall intensity increased first and then gradually stabilized. Under other rainfall densities, there was a trend of fluctuation after rapid decline, the greater the rainfall intensity and the smaller the gravel content, the more intense the fluctuation. When the gravel content was 0 and 10%, there were rills erosion on the slope surface of aeolian sandy soil accumulation, and the sediment yield rate of rill development stage was 6.74-57.40 times of that of the sheet erosion stage. The erosion process of red soil deposits could be divided into two stages: the loose particle erosion and the soil-rock erosion stage. The sediment yield rate of the loose particle erosion stage was 1.05-3.49 times that of the soil-rock erosion stage. In general, the sediment yield rate of two soil deposits increased with increasing rainfall intensity. The sediment yield rate fluctuated with the increases of gravel content at 1.0 and 1.5 mm·min-1, with a decreasing trend under >1.5 mm·min-1. The sediment yield rate of aeolian sandy soil deposits was 1.45-4.14 times of that of red soil deposits under the same rainfall and gravel content conditions. During the erosion process of aeolian sandy soil deposits, the runoff-sediment relationship changed from low sediment concentration to high sediment concentration, while there was a reverse relationship for red soil deposits. During the high sediment concentration period, the increasing rate of the sediment yield rate of aeolian sandy soil deposits was 1.94-37.60 times of that of red soil deposits. For low sediment concentration period, the decreasing rate of the sediment yield rate of red soil deposits was 1.40-21.30 times of that of aeolian sandy soil deposits. In general, the runoff power was better than the runoff shear force in describing the erosion dyna-mics of these two types of deposits. The critical runoff power increased with increasing gravel content. The critical runoff power of aeolian sandy soil deposits during the rill erosion stage (0.02-0.04 W·m-2) was two times of that of the sheet erosion stage, while the critical stream power was lower than that of the red soil deposits. These results provide a scientific reference for modelling soil erosion processes for engineering deposits.
Assuntos
Chuva , Movimentos da Água , Sedimentos Geológicos , Humanos , Solo , Erosão do SoloRESUMO
In the open pit, runoff from the platform is large discharge and rapid afflux, which often results in serious gully erosion of dump slope. The study of erosion process under catchment conditions of the platform-slope system is still backward. In this study, field scouring experiments were conducted to investigate runoff characteristics and sediment yield processes of the platform-slope system under different flow discharges (48, 60, 72 and 84 L·min-1). Our results showed that rill erosion dominated the platform-slope system under the flow discharge of 48 L·min-1, and gully was formed under 60-84 L·min-1. The flow velocity of the platform and the slope showed an abrupting-fluctuating-stable trend with the duration of discharge. The flow velocity of the platform was smaller than that of the slope, with the magnitude of reduction at 8.3%-67.1%. The highest flow velocity appeared on the up-slop/down-slope, being 18.5%-44.6% higher than that of the middle-slope. In general, the sediment yield rate of the platform and the slope varied with the duration of discharge, with the sediment yield rate of the slope being 17.4 times as that of the platform. The ratio of gully width to depth showed substantial difference between the platform and slope. The platform generally had the largest ratio than the slope. For the slope, the largest ratio appeared on the middle-slop/down-slope, being 1.36-1.93 times as that of the up-slope. The morphology of rill and gully along the platform to down-slope presented in the form of "wide and shallow-narrow and deep-wide and shallow". Rill erosion mainly concentrated in the platform and the middle slope under the flow discharge of 48 L·min-1, contributed 29.9% and 26.8% of the total erosion volume, respectively. When the flow discharge increased to 60-84 L·min-1, the largest average across-section areas (1083.25-1737.86 cm2) formed on the up-slope accounted for 36.1%-44.7% of the total erosion volume. Our results provided evidence for modelling soil and water erosion of the platform-slope system in opencast coal mine.
Assuntos
Sedimentos Geológicos , Solo , Carvão Mineral , Água , Movimentos da ÁguaRESUMO
An indoor rainfall simulation experiment was conducted to examine the hydrodynamic characteristics, erosion characteristics, and erosion dynamics mechanisms of earth (excluding gra-vel) and earth-rock (gravel mass fraction 30%) Lou soil engineering accumulation in the Loess area across different rainfall intensities and slope gradients. Results showed that the presence of gravel changed the hydrodynamic characteristics of the engineering accumulation slope. The flow velocity, froude number, unit stream power, and unit energy of water-carrying section of the earth-rock slope were 1.7%-49.7%, 6.7%-60.6%, 2.0%-44.6% and 1.0%-26.7% lower than those of the earth slope, while the Manning roughness coefficient and runoff shear stress of the earth-rock slope were 6.2%-169.4% and 5.7%-79.3% higher than those of the earth slope respectively. Under the intensity of 2.0 and 2.5 mm·min-1, erosion rate of the earth-rock slope was 26.2%-89.9% lower than that of earth slope. The gravel significantly reduced slope erosion of the Lou soil engineering accumulation. Erosion rate and hydrodynamic parameters of the two accumulations were linearly related. The erodibility parameters of earth-rock slope were 56.1%-73.3% lower than that of earth slope. In the critical hydrodynamic parameters, runoff shear stress of earth-rock slope was 11.1% higher, while the stream power, unit stream power and unit energy of water-carrying section were 25.4%, 64.0% and 5.0% lower than those of the earth slope, respectively. The existence of gravel controlled rainfall erosion process on the slope of the engineering accumulation to some extent.
Assuntos
Chuva , Solo , China , Sedimentos Geológicos , Água , Movimentos da ÁguaRESUMO
Ephemeral gully erosion is an important erosion type in hilly and gully regions of Loess Plateau. While previous studies mainly focused on ephemeral gullies in agricultural land, little is known about the effects of naturally restored grassland on ephemeral gully erosion. In this study, taking the bare ephemeral gullies as the baseline, we conducted in-situ flushing tests to explore runoff and sediment yield characteristics and erosion mechanism of grassland ephemeral gullies under the runoff conditions of 5, 10, 15, 20 and 25 L·min-1. Compared to the bare ephemeral gully, average flow velocity, stable runoff rate, Reynolds number and Froude number of grassland ephe-meral gullies was reduced by 25.4%-67.3%, 8.4%-26.6%, 54.9%-80.5%, 18.6%-65.1%, respectively, whereas resistance coefficient was increased by 0.09-7.18 folds. Compared to the bare ephemeral gully, the maximum sediment yield rate, stable sediment yield rate, average sediment yield rate of grassland ephemeral gullies was decreased by 55.1%-90.9%, 61.8%-95.4%, and 64.8%-92.4%, respectively. The sediment yield reduction benefit of the naturally restored grassland under the discharge flow rate of 5-25 L·min-1 could reach 65.9%-88.8%, which decreased with increasing discharge flow rate. Compared to the bare ephemeral gully, average stream power and average shear stress of grassland ephemeral gullies was reduced by 54.9%-80.5% and 12.4%-51.1%, respectively, whereas the critical stream power and critical shear stress was increased by 1.43 folds and 33.7%, respectively. The average sediment yield of grassland and bare ephemeral gullies was signifi-cantly linearly related to average stream power and shear stress. Naturally restored grassland significantly increased the erosion resistance and reduced runoff erosion potential of ephemeral gullies.