Sustainable method for slope stabilization and erosion control | |
| Author | Jindarat Maneecharoen |
| Call Number | AIT Diss. no.GE-12-01 |
| Subject(s) | Soil stabilization Slopes (Soil mechanics) Soil erosion |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctorof Engineering in Geotechnical and Earth ResourcesEngineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. GE-12-01 |
| Abstract | Water hyacinth fiber which is limited life geotextile(LLGs)was used in this studyfor erosion protection of soil slope in comparison to Vetiver and Ruzi grasses. The water hyacinth fibers were braided and then weave into the mesh size 8 mm x 8 mm and 12 mm x 12 mm. Thewaterhyacinth LLGs were tested as geotextile material according to ASTM standard namely: mass per unit area, thickness, tensile strength, permittivity as well as hydraulic transmittivity.Subsequently thegrowth rate of Vetiver and Ruzi grasseswere studied at planting periodsof 7, 14, 21 and 28 days, respectively. The grasseswereplanted in PVC pipe with diameter 150 mm and height of 150 mm.Then, comparison was made between samples grown in the PVC pipe coveredwithwater hyacinth LLGswith opening sizesof 8mm by 8 mm and 12mm by 12 mm to bare soil. Growth investigations included thenumber of sprouted Ruzi grasses, lengthsstem above soil surface,and lengths ofroots. The soil sample covered with water hyacinth LLGs with opening size of 8 mm by 8 mm wassuitable for sprouting, root length permeation as well as stem growing above soil surface comparedwiththeother two casesbecausethe soil sample covered with water hyacinth LLGs with opening size of 8 mm by 8 mm can retain adequate soil moisture that enhance the growth rate of Ruzi grasses.The engineering properties of sandy soil and lateritic soil were investigatedand thecontoursof rainfall intensity at 90 mm/hr and 120mm/hr were alsoestablished. Runoff rate over sandy and lateritic soilcover with LLGs or vegetationswere recorded. The effectiveness of soil covering that includewaterhyacinth LLGs and grassesmeasured bysoil loss due to surface runoff indicated the superiority of the combined Vetiver and Ruzi grasses. The test results revealedthat the surface runoff rate and soil sediment obtained from every samples increasedas inclination slope increased. Soil erosion protection using water hyacinth LLG with opening size of 8 mm by 8 mm can reduce soil loss better than the opening size of 12 mm by 12mm. On the other hand, the test results indicated that surface runoff rate and soillossdecrease as grass covering ratio increased. The most effective mitigation measure to prevent soil loss was planting a combination of Vetiver and Ruzi grasses followed by planting Ruzi grass or Vetiver grass, respectively. The surface runoff rate and soil loss measured in the 8thweek wasthe lowest because of longer growing period of grass. Consequently, the grass can grow and cover soil surface more effectivelythan the shorter growing period.The tensile test of Vetiver grass roots and Ruzi grass rootsat growing periodsof 2, 3, 4, 5 and 6 months were carried out. Relationship amongtensile strength, modulusof elasticityand diameter of the grass roots were obtained.The tensile test results of both Vetiver and Ruzi grasses roots in the laboratory revealed that the age of roots have slightly affected on the tensile strength of root. Tensile force of both Vetiver and Ruzi grasses roots were proportional to the diameter of the root. While, the tensile strength of both Vetiver and Ruzi grasses roots were inversely proportional to the diameter of the root. Furthermore, the modulus of elasticity (Young's modulus) of both Vetiver and Ruzi grasses roots were inversely proportional to the diameter of the root. Additionally, direct shear testsin the field of soilonly, soil reinforced with combinations of Vetiver and Ruzi grasses root, Vetiver grass rootreinforced soil, Ruzi grass rootreinforced soil using normal stress of 2.7, 5.5and 10.9KN/m2at growing periodsof 2, 3, 4, 5, and 6 months, respectively,were also conducted. In this study, the direct shear strength of 3 types of grass root reinforced soil and soilonlyhas been compared. At the same growing period,the shear strengthsof soil reinforced with combination of Vetiver and Ruzi grassesroot reinforced soil werehigher than that of Vetiver grass root reinforced soil, Ruzi grass root reinforced soil and soilonly. Therefore, the combination grass root system was more suitable to be applied in the field to enhance the stability of the soil slope than the Vetiver or Ruzi grass root reinforced soil alone. Moreover, the Vetiver grass root length wasapproximately 3 mlongwhile Ruzi grass root length was only100 mmlong.As such, Ruzi grass root is suitablefor prevention of soil erosion only.Shearstrength parameter of soilonlyand root reinforced soil obtained fromdirect sheartest results was used to analyzethesafety factorsof soil slopeswith inclinations of1H:1V, 2H:1Vand 3H:1V.Usinginfinite slope methods.The strength parameterincludedcohesion of soil (cS), increased cohesion due to root reinforcements(cR)fromVetiver and Ruzi grassesand internal friction angle ()andwere used as an inputparametersin slope stability analysisusing limit equilibrium (KU) software. The safety factors increased due tograssroot reinforcements. The relationship betweenthesafety of factors and growing periods indicated that the safety factors of combined Vetiver and Ruzi grassesroots reinforced soil were higher than the Vetiver orRuzi grasses root reinforced soil and soilonly, respectively. The relationship between safety factors and growing periods of soilonlyand all types of root reinforced soil with different slope inclinations indicated higher values. |
| Year | 2013 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. GE-12-01 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Bergado, Dennes T. |
| Examination Committee(s) | Pham Huy Giao;Hadikusumo, Bonaventura H. W.;Panich Voottipruex |
| Scholarship Donor(s) | Rajamangala University of Technology Thanyaburi, RMUTT,Thailand |
| Degree | Thesis (Ph. D.) - Asian Institute of Technology, 2012 |