Field Application and Investigation of the Shotcrete Vegetation Mulching Technique on Steep Slopes and A Preliminary Study on Its Material Optimum Mixture Proportion
Date Issued
2011
Date
2011
Author(s)
Chen, Yin-Chieh
Abstract
In this study, a newly developed method, namely, Shotcrete Vegetation Mulching Technique (SVMT) was applied on the slopes of Shun-tai at Shih-men Reservoir with steepnesses higher than 80 degrees. Aside from this, a preliminary study on the SVMT material optimum mixture was also carried out. Both the tests in the field and in the laboratory, including surface strength, soil pH value and vegetation coverage, were conducted on the soil surfaces with different ages.
Firstly, because of hardening effect of the concrete cement, the surface strength of the soil with the age from 3 to 7 days reached at least 2.72 kg/cm2, indicating that the SVMT method could be used to rapidly increase the strength of the soils on steep slopes. And since the soils were mixed with concrete cement, the pH values of the soils with the age less than 14 days were about 8 to9. When the ages were greater than 14 days, the soil were neutralized because of rainfall, water spraying, leaching and greening additives, the soil pH value were decreased in a stable range from 7.4 to7.9. Regarding vegetation coverage, when the age of the soil was 126 days, the vegetation cover rate had already reached at least 85%. In addition, it was also found that while the age was 84 days, the test site was invaded by native plant. When the age was 242 days, 10 native plants including mostly Spanish needles [ Bidens pilosa L. var. radiate (BI.) Sherff ] were found in the test site. From the results, it might be concluded that the method of SVMT could be applied on steep slopes, providing higher strengths within a shorter time period and habitat environments suitable for plant growing. In addition to these, native plants were allowed to invade into the areas naturally.
In regard to the study of the material optimum mixture of SVMT, three soils, namely, soils A, B and C were used. Soil A was collected from Shun-tai, Soil B was from water sludge of the water treatment plant at Gung-guan, Taipei and soil C was the sludge of Shin-men Reservoir. The three soils were mixed with concrete cement, fertilizer, soil neutralizer and grass seeds respectively. The strengths of the mixtures between 1.5 to 5.5 kg/cm2 had better vegetation coverage. Apart from this, from the test results of soil pH value and vegetation coverage, it was found Soil B mixed with ferros sulfate (FeSO4．7H2O) had better soil pH and vegetation coverage. It might be concluded that water sludge and ferros sulfate could be used as the soil and neutralizer of the SVMT respectively.
Subjects
Shotcrete Vegetation Mulching Technique (SVMT)
Vegetation coverage
Water sludge
Steep slopes
Soil neutralizer
SDGs
Type
thesis
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