Experimental study on expansive soil improved by lignin fiber-high calcium fly ash composite
To improve the shortcomings of a single method to improve expansive soil,this paper adopts the method of composite improvement,and selects lignin fiber and fly ash(high calcium)to improve expansive soil.Based on the reuse of production waste,it is used in the improvement project of expansive soil in Mengzi,Yunnan to inhibit the expansion deformation of soil and improve the strength,failure toughness and water stability of improved soil.The optimal dosage of fly ash is obtained by free expansion rate,loaded expansion rate(50 kPa),unconfined compressive strength test,and low-stress direct shear test of improved soil.The mechanical strength test,water stability test,and micro test are carried out by adding lignin fiber,and the composite improvement effect is analyzed by mechanical properties and microstructure characteristics.The test shows that:(1)When fly ash is added alone,the expansion characteristics of the improved expansive soil are inhibited,the expansion rate is greatly reduced,the unconfined compressive strength and shear strength are improved,and the cohesion changes significantly;(2)With the increase of curing age,the unconfined compressive strength of the improved soil can be significantly improved,the failure mode of the sample is improved,the existence of the fiber increases the failure toughness,and the water stability is also greatly enhanced.The composite improvement effect of 20％fly ash and 1.0％lignin fiber is the best.(3)There are tiny pores in the plain expansive soil,and cracks are developed.After the improvement,the pore distribution in the soil is improved,and the large pores become small pores.The generated cemented particles fill the cracks,and the particles gather together to enhance the compactness of the soil.Fiber incorporation inhibits the extension of soil cracks and contributes some strength to the soil's resistance to external forces.
NETL
NSTL
万方数据
维普
