Theoretical Research on Sand Penetration Grouting Based on Cylindrical Diffusion Model of Tortuous Tubes

Abstract

The penetration paths of grouts in sand layers are tortuous, and there is no reasonable penetration grouting theory at present. By employing tortuous circular tubes as the internal penetration pore channels of the sand layer, the cylindrical diffusion model is established for sand-layer penetration grouting. First, the permeability of porous media and average penetration velocity of Bingham slurry were deduced by considering tortuosity. Second, based on the penetration continuity equation, the active steady-state penetration differential equation of Bingham slurry and the pressure distribution function of slurry in the diffusion region were obtained. Finally, combined with the indoor penetration grouting test results, the attenuation law of slurry pressure and the influencing factors of diffusion radius were discussed. The results show that the cylindrical diffusion model of tortuous tubes can better characterize the diffusion process of penetration grouting in the sand layer. The stop condition for diffusion during penetration grouting is the reduction of the pressure gradient of the slurry to its starting value. The slurry pressure attenuation has obvious stages. The slurry pressure attenuation is faster in the area close to the grouting tube. At 50% of the maximum diffusion radius, the pressure attenuation is 70.01~75.41% of the total pressure attenuation within the diffusion region. Increasing the grouting pressure and permeability coefficient and reducing the slurry viscosity ratio can greatly increase the slurry diffusion radius. These results provide a theoretical basis for determining sand grouting parameters in the future.

Pressure Model Study on Synchronous Grouting in Shield Tunnels Considering the Temporal Variation in Grout Viscosity

“…According to the existing research, the grout viscosity considering the temporal variation can be expressed as [20,35]:…”

“…The grout diffusion quantity and range are difficult to obtain during synchronous grouting in shield tunnels. A typical empirical equation of the diffusion distance is proposed by Wang et al (2022) [35]:…”

Theoretical Research on Diffusion Radius of Cement-Based Materials Considering the Pore Characteristics of Porous Media

“…Take a circular tube with radius , and select the stress state of a microfluidic column with radius and length , as shown in Figure 3 . Without considering the gravity of the slurry, the equation of the force balance in the horizontal direction of the micro-fluid column is as follows [ 18 , 36 ]: …”

“…Ye et al [ 9 ], Floar et al [ 10 ], and Yang et al [ 11 , 12 ] studied the column and column-hemisphere diffusion of power-law slurry in sandy (gravelly) strata based on penetration theory, but did not consider the time-varying viscosity of the slurry. Lv et al [ 13 ], Zhang et al [ 14 ], Cheng et al [ 15 ], Liu et al [ 16 ], Li et al [ 17 ], Wang et al [ 18 ], and Liu et al [ 19 ], combined with theoretical analysis and experimental verification, explored the crack diffusion law of a single slab based on the time-varying viscosity of the slurry, and discussed the influence of the time-varying viscosity of slurry on fracture grouting. Guo et al [ 20 ] used COMSOL numerical simulation software to verify the theoretical results of penetration grouting in sandy (gravelly) strata and analyzed the influence of the time-varying viscosity of slurry on the penetration diffusion of slurry in sandy (gravelly) strata.…”

Grouting mechanism and experimental study of goaf considering filtration effect

“…The filtration effect in the slurry infiltration process is an essential factor affecting slurry diffusion [15][16][17]. The main research methods include four [18]: a macro model based on macro experimental phenomena, the study of the analysis method of single particle trajectory of suspension, the method of studying congestion through probability, and the mesh model method.…”