Mechanical Properties Of Fiber Composite Solidified Loess And Its Application In Slope Engineering

With the rapid development of China’s economy,the infrastructure construction in the Loess Plateau is accelerating.Due to its special topography and engineering geological conditions,it is necessary to reinforce the Loess in different degrees in the construction of the project.When the curing agent is used alone,it is easy to have some shortcomings,such as low tensile strength,poor plasticity and large shrinkage coefficient.In order to improve the above situation,based on the solidification treatment of loess,the green basalt fiber material is added for composite improvement.Through a series of indoor geotechnical tests,the effects of fiber length,dosage and confining pressure on soil compaction performance,strength parameters,stress-strain curves and failure modes were studied.The internal mechanism of basalt fiber improving the properties of composite soil is further analyzed through the microscopic experiment of scanning electron microscopy.Finally,based on the experiments,the stability of the improved high fill slope was analyzed by Geo Studio software modeling.The main research contents are as follows:(1)Experimental study on the compaction performance of loess with lime,fly ash and lime ash curing agent under different dosages,and summarize the differences and rules of the performance parameters of loess under different conditions;The results of limited compression test were carried out to analyze the range and variance.The design of the optimum mixture ratio of curing agent,dosage,age and water content of Xi’an loess was proposed.The dip angle of the fracture surface of the specimen was studied and proposed.The range of angle of the rupture angle under different mixing ratios provides a reference for the curing agent improvement scheme in the region.(2)Based on the optimal mix ratio of solidified soil,the complete orthogonal test of basalt fiber composite soil with different lengths and dosages was designed.The fiber length was analyzed by unconsolidated undrained triaxial test.The influence of the amount and confining pressure on the strength parameters,stress-strain curves,etc.,and the evaluation coefficient of the influence on the soil parameters is calculated by the grey correlation theory.The experiment shows that the fiber mainly changes the cohesive force of the loess,and has little effect on the internal friction angle.The stress-strain curve gradually decreases with the increase of the confining pressure,and the sample exhibits obvious plastic deformation and damage.(3)By studying the existing splitting test theory,an experimental device suitable for the splitting and tensile test of the axial fracturing method is proposed,and the reasonable size of the test piece is demonstrated to realize the tensile strength of the fiber composite soil.The tensile strength and stress-filling depth curves of different fiber lengths and dosages were studied.Combined with the above experimental results,the fitting formula of the relationship between tensile strength and cohesion of basalt composite soil was proposed.The principle of fracture mechanics is used to statistically analyze and explain the crack tip extension form and the integrity of the test piece.(4)Electron microscopy scanning of the microstructure of plain soil,lime soil and fiber composite soil,qualitative analysis of the internal strengthening mechanism of soil ash and fiber through the chemical reaction and fiber mesh respectively to improve the strength of the soil,and soil-gluten interface and fiber failure modes are summarized.Through software,the morphological characteristics,spatial arrangement characteristics and fractal dimension of soil pore particles were quantitatively analyzed.The experimental results show that the improved loess has good fractal characteristics.(5)Establishing a high-filled slope model under different improvement schemes,and demonstrating the engineering feasibility of reinforcing the slope with fiber composite soil by analyzing the overall stability of the slope,and the slope safety factor of the slope under different algorithms.Fit,propose an exponential fitting equation for the safety factor.