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This study was conducted to quantitatively evaluate the reservoir damage caused by waterflood-induced velocity sensitivity in the tight oil reservoirs of Block L in the Ordos Basin. This research investigated changes in reservoir pore–throat structure before and after waterflooding through laboratory experiments. A velocity sensitivity characterization model was established as RcQ=Qexp⁡−βvc01+λQηδ2πϕhvc01+λQη, and the injection volume as Q, and its reliability was validated using both experimental and field data. The results indicate that excessive water injection can lead to permeability damage in the reservoir. Based on this model, the optimal injection rate for Block L was determined to be 16.8 m3/day. Field application of this optimized rate reduced velocity sensitivity-induced particle damage by 21% and improved oil recovery by 1.4%.

Common problems in horizontal grouting engineering projects that it is difficult to evaluate the grouting slurry diffusion range due to theoretical limitations. Here we report a novel experimental design that investigates the influence of grouting parameters (grouting time, pressure, slurry water-cement ratio) and permeability coefficient on grouting slurry diffusion in order to determine the diffusion law of horizontal grouting in shallow sand gravel layer. The results indicate that grouting pressure is sensitive to the most significant impact on the slurry diffusion radius, and the following rank is grouting time > slurry water-cement ratio > permeability coefficient of the stratum. Next, discrete element software was employed for single-factor analysis. Finally, a numerical model of shield tunnel settlement was developed to evaluate the impact of grouting reinforcement on ground settlement. The findings reveal that the slurry diffusion exhibits a non-standard columnar shape with horizontal symmetry, while the permeability coefficient of the sand and gravel influences vertical diffusion.

Grouting technology is an important method that has been widely adopted for the crack repair of tunnel lining, but the diffusion law of grouting slurry is still uncertain in tunnel lining cracks. For the sake of exploring the grouting diffusion law of tunnel lining cracks, this paper investigated the grouting diffusion shape and the relation between the diffusion radius and time with different crack widths in tunnel lining which by means of laboratory experiments and statistical analysis. Meanwhile, the diffusion equation of grouting in lining cracks has been established on basis of the grouting diffusion shape and experimental data. Furthermore, it is analyzed the correlation between the experimental values and the calculated values. The results revealed that the diffusion shape can be divided into a circular zone, excessive zone, and elliptical zone in the tunnel lining cracks, and the calculated values of the equation of grouting diffusion are highly correlated with the experimental values. Additionally, it is shown that the diffusion equation can accurately describe the relationship between diffusion radius and time of grouting in tunnel lining cracks. The study results would provide a theoretical basis for the prediction of diffusion radius on grouting repair for tunnel lining cracks.

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.

In underground project, water inrush disaster often occurs, resulting in a large number of casualties and economic losses. To solve these problems, grouting is one of the main techniques for controlling water inrush. At present, the research results on the treatment of water inrush by grouting are based on anhydrous or hydrostatic grouting. However, the study of dynamic water grouting is relatively few and the grouting materials are a little bit. In this paper, water-soluble polyurethane was selected as grouting material, modified by adding hydroxypropyl methyl cellulose, and the bond strength and microstructure change before and after modification are studied via bond strength experiment and microscopic observation. In addition, the WPU (water-soluble polyurethane) diffusion regularity of dynamic water grouting is studied by indoor flat grouting test. The research also adopts the Bingham fluid model according to the slurry characteristics to derive the grouting diffusion radius. The results show that the compactness of HPMC (hydroxypropyl methyl cellulose)-WPU is improved, the heterogeneity is reduced by 50.4%, and the bonding strength is increased by 153%. Therefore, the anti-scour ability of the HPMC-WPU is enhanced. The deviation of the WPU in the X-axis diffusion radius is 7.7 cm, and the HPMC-WPU is 4.39 cm. What’s more, the formula of grouting diffusion radius is derived. By comparing the formula with experiment results, the deviation is less than 15%, therefore, the formula has the significance of guiding engineering practice.

Previously conducted studies have established that the soil–rock mixture in the Chongqing area has the characteristics of loose structure, poor stability, strong permeability, and so on. When building a tunnel in a soil–rock mixture stratum, it is necessary to reinforce the surface rock mass and surrounding rock by grouting to improve the safety of tunnel excavation. To study the diffusion mechanism of cement slurry (Bingham fluid) in soil–rock mixtures, based on the Bingham fluid flow equation and slurry diffusion model, the Bingham fluid fracture diffusion formula was derived, and field grouting tests and indoor model tests were carried out with soil–rock mixtures in the Chongqing area as the research object. The fracture grouting diffusion formula was verified and analyzed using the test data. The research results show that the theoretical calculation results of various working conditions are close to the actual test results (the error of indoor model test results is less than 3%, and the error of field test results is less than 5%). A Bingham fluid fracture diffusion formula has been developed that applies to various working conditions of fracture grouting of soil–rock mixtures and has a good prediction effect on the value of the fracture diffusion radius.

Due to high reactivity and relatively low cost, nano zero-valent iron (nZVI) has become an alternative material for in-situ remediation of contaminated sites. However, factors such as short transport distance and easy deposition in porous media also seriously restrict its injection remediation effect. The optimum ratio of bentonite and kaolin supported nano zero-valent iron (K-nZVI) in the remediation agent was determined by sedimentation and rheological tests. The transport characteristics of deionized water and bentonite suspensions carrying K-nZVI in porous media under different injection pressures were investigated using simulating column tests. The results show that bentonite suspensions could significantly improve the stability and dispersibility of K-nZVI. The proportion of bentonite and K-nZVI are 5% and 0.4%, respectively, which is the best ratio of the remediation agent. The transport capability of K-nZVI carried by deionized water increases with the increase of injection pressure, while there is a critical injection pressure for bentonite suspensions carrying K-nZVI remediation agent. The numerical simulation results show that the diffusion radius of K-nZVI is positively correlated with the injection pressure and negatively correlated with the viscosity of the remediation agent. The results provide theoretical guidance for the remediation project of heavy metal pollution in non-ferrous smelting sites.

The soft surrounding rock of deep roadways is in the state of “micro-fracture and low permeability”. In order to solve the problem of grouting reinforcement of micro-fractures surrounding rock in deep roadways, the influence characteristics of auxiliary materials and additives on slurry flow were analyzed, and the composition and proportion of superfine cement-based composite grouting materials were determined: superfine cement accounted for 89.4%, superfine coal ash accounted for 5%, ultrafine mineral powder accounted for 5%, naphthalene water reducing agent accounted for 3~5‰, and lignin sulfonate calcium accounted for 1~3‰. The effects of water–cement ratio and water reducer content on slurry viscosity and water bleeding rate were tested by laboratory experiments. Based on the fracture characteristics of surrounding rock and the “Liu Jiacai Formula”, the influence law of fracture opening, grouting pressure and slurry viscosity on the slurry diffusion radius was analyzed. The results show that the slurry viscosity decreases with the increase of water–cement ratio and water reducer content, but the bleeding rate increases obviously with the increase of the two factors; when the water–cement ratio is 1.0 and the water reducer content is 3‰, the slurry has the advantages of “strong permeability, strong flow and low water bleeding rate”; the smaller the fracture opening is, the greater the required grouting pressure and the lower the required slurry viscosity. Aiming at the “micro-fracture zone” of surrounding rock in deep roadways, when the dynamic viscosity of the slurry is 2.0 mPa·s, the reasonable grouting pressure should be 12 MPa to meet the needs of grouting reinforcement engineering. The high-pressure grouting test of surrounding rock in the “micro-fracture zone” was successfully carried out by using the superfine cement-based composite grouting material.

To conduct pro-grouting design and make the prediction of the result of grouting about the chunnel that passes through fractured rock mass, the essay adopts following theoretical formula to calculate the fractured rock mass grouting diffusion radius: Wittke and Wallner Formula、Lombadi Formula and Huang Chunhua Formula. Finally through the analysis of calculation results can conclude: (I) The diffusion radius of the slurry can meet the design requirements under the condition of 3-4 Mpa designed grouting pressure、5 cm grouting holes’ radius and 1800-3600s grouting time. (II) The calculation result of Huang Chunhua Formula is almost the same as Wittke and Wallner Formula and Lombadi Formula, but the margin of grouting diffusion radius’ change as grouting time and grouting pressure growing are different, it’s more close to the real situation.(III) The calculation of these theoretical formula only consider the breadth of fractured rock without considering the variation of its thickness and direction. So all of the calculation results of these formula are generally bigger than the standard.

The influencing factors of grouting diffusion in broken rock mass were divided into four classifications: grouting pressure, grouting time, permeability coefficient and grout viscosity. Relations among similar factors were expressed to each other using an equation. Empirical formulas of relations among grout water-cement ratio, viscosity and time between the joint density of broken rock mass and permeability coefficient, and between water absorption and permeability coefficient were established. The differences among the four diffusion radius formulas grouting in porous continuous media were compared. A new empirical formula of diffusion radius was obtained using multivariate nonlinear fitting analysis based on the mean value of the four empirical formulas. The tests of grouting diffusion in broken rock mass were done in the field. The mean empirical formula is consistent with the measured value of the field tests on grouting diffusion radius, which provide a reference for the design of grouting into broken rock mass.