| Coir fiber is a natural fiber material with the advantage of being renewable and having good tensile properties.When coir fiber is incorporated into the soil,it can be linked with soil particles to form a new soil structure,which has good shear strength and flexibility and can improve the cohesion and internal friction angle of red clay soil.At present,coir fiber reinforced soil has been practiced and researched in China,but most of the researches focus on the improvement of shear strength of soil by coir fiber,but there are few researches on the mechanical properties of coir fiber reinforced soil under static and dynamic action,and there are few cases of simulating actual engineering applications.Based on this,this thesis investigates the effects of coir fiber admixture,fiber length,vibration frequency and surrounding pressure on the static and dynamic properties of coir fiber reinforced soils through triaxial tests using larger triaxial specimens,and analyses the influencing factors.Finally,Midas GTS/NX was used to verify the safety of the slopes reinforced with coir fiber,by determining the parameters of the model material through static and dynamic triaxial tests,inputting some boundary conditions from the actual project into the slope model,and carrying out numerical simulation analysis of the plain soil slopes and the coir fiber reinforced soil slopes.The main research contents of this thesis are as follows.(1)A series of basic geotechnical tests were conducted to measure the mechanical parameters of the red clay and coir fiber to provide a reference basis for the fabrication of specimens for static and dynamic triaxial tests.These include natural moisture content,liquid limit,plastic limit,soil density,specific gravity,optimum moisture content and tensile properties of coir fiber.(2)A static triaxial test was carried out to determine the effects of the amount of coir fiber incorporated,the surrounding pressure and the fiber length on the stress-strain curve of coir fiber reinforced soils.The Duncan-Chang model is then correlated with the properties of the coir fiber reinforced soil,and the equations are fitted by Origin data processing software to produce a modified Duncan-Chang model based on the coir fiber reinforced soil.The modified Duncan-Chang model was used to predict the stress-strain curve pattern of the coir fiber reinforced soil,and the predicted curve was plotted against the test curve.(3)Based on the dynamic triaxial test,the dynamic backbone curve of coir fiber reinforced soil is plotted and the Hardin-Drnevich model is introduced to investigate the properties of reinforcement rate,vibration frequency and surrounding pressure of coir fiber reinforced soil.The Hardin-Drnevich model is then used to correlate the a and b parameters of the Hardin-Drnevich model with the properties of the coir fiber reinforced soil.The Hardin-Drnevich model was then used to predict the dynamic backbone curve of the coir fiber reinforced soil,and the predicted curve was plotted against the test curve.(4)Two numerical slope simulations,one for a plain soil slope and the other for a slope reinforced with coir fiber,were developed using Midas GTS/NX software to investigate the force characteristics of the slope under loading conditions and the effect of coir fiber on the slope displacement and factor of safety,the maximum shear strain and the plastic zone.The results of the model calculations show that coir fibers can also effectively reduce the maximum shear strain,reduce slope displacement and increase the slope safety factor.In addition,coir fibers can effectively reduce the stress concentration in the slope and improve the stress distribution in the plastic zone of the slope,thus improving the stability of the slope.In this thesis,the effect of coir fiber on red clay soils is investigated through static and dynamic triaxial tests,and the influence of different factors such as reinforcement rate,vibration frequency,fiber length and surrounding pressure on coir fiber reinforced soils is studied.A comparative analysis of the applicability of this model was carried out.Finally,numerical simulations are carried out by simulating the plain soil slope model and the coir fiber reinforced soil slope model.Some of the results obtained from the above study provide a reliable test basis for further experimental research on coir fiber reinforced soils and provide an important reference for the future application of coir fiber reinforced soils in engineering. |
