Investigation Into The Characteristics And Strength Simulation Test Of The Complex Two-component In Synchronous Grouting Of Shield Tunneling

Shield tunneling method has become one of the main methods in the field of tunnel engineering because of its safety,high efficiency and high quality.As an important step in the process of shield driving,synchronous grouting is very important for the control of surface settlement and the mitigation of surrounding rock deformation.The grouting material is divided into single-component and two-component,overall,two-component has been widely applied in the synchronous grouting of soft soil layer and water rich stratum by virtue of short gel time and high early strength.However,the traditional two-component has poor durability,poor water resistance and high cost.Based on the traditional two-component,the complex two-component with fly ash and slag to replace part of cement,making use of the characteristics of alkali activated fly ash and slag activity,and ultimately forming dense solid structure by C-S-H gel with low CaO/SiO2 and amorphous zeolite like substances with good durability,effectively improves the durability,while reducing the cost.This paper carried out the test on the complex two-component properties,investigating into the effects of powder proportion,sodium silicate content and W/C ratio on flowability,stability and gelling property.Then,the best mix proportion for shield tunnel synchronous grouting was obtained.Meanwhile,the influence of the powder mixing procedures on the properties of the fresh A-component and the influence of curing conditions on the compressive strength of the complex two-component were studied.In addition,the circular specimen was placed in the simulated stratum to study the strength development law of the the complex two-component.The results show that:(1)With fly ash and slag replacing part of cement,grout fluidity decreases about 10%,the early strength decreases from 10%to 15%,but the gel time is prolonged by 40%～80%,A-component bleeding rate decreases by 32%.When the sodium silicate content is 0.25～0.3,the flowability is improved,the gel time is easy to control,and the compressive strength is high enough.With the increase of W/C ratio,the fluidity is increased,and the gel time is prolonged.(2)When mixing,two times adding mixing water causes the A-component bleeding rate increased by about 15%and flowability enhancement;two times adding powder will lead to the A-component bleeding rate decreased by about 20%and flowability enhancement.Under the premise of meeting the engineering requirements of the bleeding rate(<5%),two times adding mixing water is in favor of the A-component flowability.(3)With the power function curve fitting,the rebound strength curve of the complex two-component is obtained.The relative error is less than 10%,and the correlation coefficient is 0.74.The curve can determine the relationship between rebound value and compressive strength.Curing in the simulated stratum,the 7d compressive strength of the circular specimen is 12.5MPa and the 14d is 28.6MPa.This proves that the complex two-component is suitable for synchronous grouting.