Grout Volume Research Articles

Measurement and analysis of surface settlement caused by construction of quasi-rectangular shield tunnel in rich water-sand stratum.

The study is based on a section of the Zhengzhou Metro Line 8 quasi-rectangular shield tunnel. Field excavation trials were conducted to analyze the surface settlement patterns caused by the construction of a large-section quasi-rectangular shield tunnel in the rich water sand layer in Zhengzhou. Based on the characteristics of the rich water sand layer, ground settlement control measures were proposed. The research findings show that the surface settlement caused by the construction of the large-section quasi-rectangular shield tunnel in the rich water sand layer exhibits a temporal curve pattern of slow settlement (Stage I: pre-arrival of the shield), rapid settlement (Stage II: shield passage, Stage III: shield tail exiting 14.4 ~ 18m), and stable settlement (Stage IV: late settlement). In Stage I, controlling the excavation rate to maintain balance between the cutter face pressure and soil pressure is effective. In Stage II, injecting lubricating mud between the shell and the sand layer to reduce soil friction and shear slip is recommended. In Stage III, increasing the synchronous grouting volume at the shield tail and adjusting grouting pressure, as well as timely filling the shield tail construction gap, are effective methods to reduce surface settlement. The Peck formula was used to fit the transverse settlement trough on the surface, with a linear correlation coefficient R²=0.983, validating the use of the Peck formula to predict surface settlement troughs for quasi-rectangular shield tunneling in the rich water sand layer. These research findings can provide data support and reference for similar projects.

Study on the Diffusion Characteristics of Polymer Grouting Materials Applied for Crack Filling in Underground Mines Based on Numerical Simulation and Experimental Methods.

Polymer grouting materials are increasingly used in the filling of mine fissures. Unlike conventional inorganic grouting materials, the self-expansion of polymers adds complexity to their diffusion process within the crack. The objective of this research was to examine how polymer grouting material spreads in cracks at ambient temperatures and pressure. The investigation involved conducting grouting tests and performing numerical fluid simulation calculations using the finite-volume method in the computational fluid dynamics software, ANSYS FLUENT 2022 R1. The fluid volume approach was employed to determine the boundary between fluid and air and to ascertain the variation patterns of density in the slurry and the fracture system. This study applied the principles of fluid mechanics to investigate the patterns of variation in the physical characteristics of polymer grouting materials, including their density, pressure, flow velocity, and movement distance, during the diffusion process. The results indicated that the density of the polymer grouting material decreased exponentially over time throughout the diffusion process. With the increase in the grouting's volume, the grout's pressure and the permeable distance of the grout increased. The slurry's pressure near the grouting hole exceeded the other points' pressure. The physical parameters of the slurry were numerically simulated by ANSYS FLUENT 2022 R1 software, and the results were compared with the experimental data. After comparing the numerical simulation results with the test data, it was clear that the numerical simulation method was superior in accurately predicting the distribution pattern of each parameter of the polymer slurry during diffusion. The grouting volume, pressure distribution, and real-time change in the position of the flow of slurry could be efficiently determined through numerical calculation and simulated grouting tests. This work can offer valuable information for designing polymer grouting materials used in underground mine fissures.

Horizontal bearing capacity of post-expanded arm grouting pile foundations

In order to effectively improve the horizontal bearing capacity of pile foundations, this study proposes post-expanded arm grouting technology and associated pile foundations. The horizontal bearing characteristic of the post-expanded arm grouting pile was explored through model tests. The test results indicate that the post-expanded arm grouting pile can increase the contact area between the pile and soil, and can improve the strength of the soil. The horizontal bearing capacity of the post-expanded arm grouting pile was approximately 3 times that of the conventional pile. It also shows that the larger the plate diameter ratio or grouting volume, the higher the horizontal bearing capacity of the post-expanded arm grouting pile. The maximum bending moment of the post-expanded arm grouting pile was located at the pile plate, and the displacement zero point of the new pile was higher than that of the conventional pile. The soil resistance at the pile plate was significantly higher than that of conventional piles, indicating that the pile plate effectively enhances the soil resistance. The improved p-y curve model and horizontal bearing capacity calculation method for the post-expanded arm grouting pile were proposed by considering the pile plate diameter factor. This method was finally verified by experimental results. The results of this study can provide a reference for calculating the horizontal bearing capacity of the post-expanded arm grouting pile.

The influence range of the biogas desaturation method for mitigating sand liquefaction

To clarify the influence range and saturation distribution after the biogas desaturation method is applied, a three-dimensional model is established with TOUGH2 software to analyze the effect of construction parameters such as grouting volume, grouting rate, grouting depth, nitrogen source concentration, and soil porosity. After that, the sensitivity of the parameters on the influence range is determined. The grouting volume and soil porosity are the most sensitive to the lateral and vertical influence range, respectively. This study provides a basis for the engineering practice of treating liquefiable subgrade by the biogas desaturation method.

Numerical analysis of underground displacements stirred by compaction grouting during tunnel construction

Compaction grouting is widely accepted to mitigate the surface settlements during tunnel excavation. Currently, compaction grouting relies heavily upon field observations due to the limit understanding of the amounts of soil displacements induced by a given volume of grout. In this study, parametric studies and probabilistic investigations are performed to examine the underground displacements caused by compaction grouting during tunneling. Under high injection pressure, soils flow around the center of a circle, which is approximately 2 m ∼ 2.8 m above the elliptical grouting bulbs and 3.3 m away from the far-end elliptical grouting bulb. An influenced zone, outside which effect of the burial depth of grouting bulbs can be neglected, is determined by connecting the intersections of vertical displacements curves. Influence of burial depth of elliptical grouting bulbs on vertical displacements is greater than that of the total length of elliptical grouting bulbs. When the total volume of elliptical grouting bulbs is identical, better grouting efficiency is achieved by increasing the volume of the elliptical grouting bulbs adjacent to the tunnel center, especially for deeper monitoring points. Locations of the maximum lateral displacements in soils are within a band underground. Moreover, probability of exceedance of vertical displacements on the tunnel center line and formulas describing the distributions of heaves in soils are presented for the benefit of assessing the project risk and liability and predicting the heaves in soils.

Surface Settlement of Shallow Shield Tunneling: Face Pressure, Tail-Void Grouting Pressure, and Grout Volume

Surface Settlement of Shallow Shield Tunneling: Face Pressure, Tail-Void Grouting Pressure, and Grout Volume

Model tests and numerical simulations of deformation repair effect for operating shield tunnels under horizontal lateral grouting

To address the large deformation problem of operating straight-joint assembled shield tunnels in soft soil, horizontal lateral grouting is often used. Using an independently designed and developed lateral grouting test device, a horizontal lateral grouting model test was conducted to study the tunnel force state and deformation repair law under the action of lateral grouting. The mechanical responses of tunnel under single-hole grouting (SHG) and two double-holes grouting (DHG) cases were comparatively analyzed, and the test results were further validated via numerical simulations. The results indicate that several key indicators of tunnel behavior, including additional pressure, bending moment, radial displacement, convergence deformation, and ellipticity, exhibit a positive correlation with the grouting volume and a negative correlation with the distance to the grouting point when implementing SHG. Expect for radial displacement, all of these metrics caused by DHG were greater than those caused by SHG. The horizontal radial displacement increases under same-side DHG but decreases under different-side DHG. Interestingly, same-side DHG is more favorable for reducing internal force and repairing tunnel deformation, and effectively improves tunnel differentiated deformation state along the longitudinal direction. However, different-side DHG can provide a better effect for transverse convergence deformation repair under the premise of minimizing tunnel overall displacement.

An environmental-benign method to enhance hydrate production in clayey silty reservoir via splitting grouting

During the pivotal period of energy transition between carbon neutrality and carbon peaking, it is crucial to develop the natural gas hydrate (NGH) due to the advantages of high energy density and non-pollution. However, the NGH production also faces several significant environmental challenges that need to be addressed such as seawater intrusion, methane leakage, and submarine landslides. Therefore, an environmental-benign method to enhance hydrate production in clayey silty reservoir via splitting grouting was introduced. As a novel method for achieving the two goals of both reservoir skeleton reinforcement and permeability enhancement, is proposed to stimulate NGH reservoir. Herein, the formulation based on foamed ultrafine cement-based grout was established. The results showed that the grout has good fluidity with initial viscosity ∼500 mPa·s and consolidation time in the range of 28–50 min. Meanwhile, the consolidation performance evaluation was studied, and it showed that the consolidation is with porosity in the range of 9.41%–46.59%, permeability in the range of 51.23 mD-789.07 mD, and compressive strength in the range of 3.31 MPa–3.88 MPa. The internal pore channels are uniformly distributed with a large number of stomatal strings, which can be used as a multistage seepage channel for gas and water production from hydrate decomposition. To further examine the stimulating behavior, the effect of hydrate saturation, grouting well diameter, grouting flow rate, and in-situ stress on splitting pressure and grouting volume were analyzed, and it was found that the grout has good ability to split fracturing and grout diffusion under the conditions of axial pressure of 5 MPa, confining pressure of 4 MPa, and hydrate saturation not more than 0.30. In addition, an environmental-benign high-efficient reservoir stimulation method on a laboratory scale was proposed. The findings could provide fundamental insights and recommendations for the implementation of splitting grouting in NGH reservoirs.

Study on Vertical Bearing Capacity of Pile Foundation with Distributed Geopolymer Post-Grouting on Pile Side.

To study the applicability of the new geopolymer grouting material for super-long and large-diameter post-grouting bored piles in silty fine sand geology, this paper compares the bearing capacity of two grouting materials, geopolymer and normal Portland cement, and different grouting volume pile side-distributed grouting piles in silty fine sand based on field model tests are analyzed through the diffusion forms of the two materials in silty fine sand through the morphology of the grouted body after excavation. The results show that the ultimate bearing capacities of P0 (ungrouted pile), P1 (8 kg cement grouted pile), P2 (6 kg geopolymer-grouted pile), P3 (8 kg geopolymer-grouted pile) and P4 (10 kg geopolymer-grouted pile) are 5400 N, 8820 N, 9450 N, 11,700 N and 12,600 N, respectively, and that the ultimate bearing capacity of the grouted pile is improved compared with that of the ungrouted pile since, under the same grouting amount, the maximum bearing capacity of the pile using geopolymer grouting is increased by 133% compared with that of the pile with cement grouting. This further verifies the applicability of the geopolymer grouting material for the post-grouting of the pile foundation in silty fine sand. Under the action of the ultimate load, the pile side friction resistance of P1, P2, P3 and P4 is increased by 200%, 218%, 284% and 319% compared with that of P0. In addition, the excavation results show that the geopolymer post-grouting pile forms the ellipsoidal consolidation body at the pile side grouting location, which mainly comprises extrusion diffusion with a small amount of infiltration diffusion, and the cement grouting pile forms a sheet-like consolidation body at the lower grouting location, which primarily comprises split diffusion. This study can provide a reference basis for the theoretical and engineering application of post-grouting piles using geopolymers.

Numerical investigation into effects of rheological properties on grout flow in rock fracture using Herschel-Bulkley model

Grouting is an essential technique for reducing the hydraulic conductivity and enhancing the strength of rock mass used in the Dongzhuang hydro-junction project. The rheological properties of grout are not to be disregarded during grouting. In this study, a numerical grouting model is established by combining a modified Herschel–Bulkley (HB) rheology model with the level set method. The effects of rheological parameters (power-law index n, consistency coefficient k, and yield stress τ0) on distribution pattern and flow characteristics of the grout are investigated. The HB model is more effective and precise than the Bingham model for predicting rheological characteristics. Numerical results indicated that distribution pattern and grout volume are primarily determined by n. A low shear rate inhibits the horizontal distribution and reduces the filling capacity of the grout, thus resulting in minimal deposition in the fracture. Grouts with a higher n and k require higher pressure to distribute around the fracture. The reduction in water volume in the fracture is calculated to provide comprehensive understanding into the sealing efficiency of the grout by varying the rheological parameters. This study provides valuable guidance regarding the different rheological parameter of grout in fractures, in addition to a novel concept for the optimal design of grouting distribution.

Source reduction and end treatment of acid mine drainage in closed coal mines of the Yudong River Basin.

After the closure of the Yudong coal mine, the pH value was approximately 3.0, and the Fe and Mn concentrations reached 380 and 69 mg/L, respectively, in the acid mine drainage (AMD), causing serious pollution to the water bodies in the nearby watershed. Combined with the formation conditions of AMD, the comprehensive treatment technology of source reduction-end treatment is adopted to treat the AMD. The treatment area of the goaf is 0.3 km3, the filling and grouting volume is about 6.7 m3, and the curtain grouting volume is 4,000 m3. Through the grouting and sealing treatment in the goaf, the water volume is reduced to less than 85% of the initial volume (100 m3/h). After the end treatment, the pH value of the effluent is around 7.0, the content of Fe and Mn is less than 0.1 mg/L, and the removal rate is above 99%. The project was subsequently operated at RMB 0.85 yuan/t. This project is aimed at the treatment of AMD from small coal mines in complex terrain conditions. It has the characteristics of low cost and high efficiency and can provide an effective treatment technology for AMD in southwestern China and areas with the same geological conditions.

Analysis of the effect of grouting parameters on pile-soil interaction of grouted piles

Reasonable control of grouting parameters was the key to improving the pile-soil interaction. However, quantitative analysis on the effect of grouting parameters on the pile-soil interaction was still lacking. This article developed an intelligent post-grouting system for precise control and quantitative analysis of grouting parameters. The conventional preparation method for shear tests were improved in this article. By changing the normal stress of the pile-soil interface during grouting, the test sample could simulate the grout distribution of the pile-soil interface at different depths. Through the improved experimental methods, a more accurate analysis of the mechanism for the pile-soil interaction was achieved. And the effectiveness of the intelligent post-grouting system was further verified by the case application. The results indicated that increasing the grout volume could improve the interface shear strength when the normal stress and grouting pressure were constant. This improvement effect caused by increasing grout volume decreased when the normal stress was high. Increasing the grouting pressure increased the interface shear strength when the normal stress and the grout volume remained constant. This improvement effect caused by increasing grouting pressure decreased when the grout volume was small. By appropriately controlling the two grouting parameters, the cohesion and the shear strength of the pile-soil interface were increased by 5.8–18.8 times and 1.16–2.91 times, respectively. The results indicated that the intelligent post-grouting system could accurately control the grouting parameters and effectively improve the pile-soil interaction of bored piles. The intelligent post-grouting system effectively reduced geotechnical engineering risks and improved the bearing capacity of pile.

Experimental study on the diffusion characteristics of nonaqueous reactive expansive polymers in sand and gravel media under dynamic water conditions

Grouting is an effective method to solve water inrush from sand and gravel. However, due to the self-expandability of nonaqueous reactive expandable polymers, the diffusion behaviour of polymers in injected media becomes more complex, which brings great uncertainty to the selection of grouting parameters in grouting practice. For this reason, a series of diffusion experiments of nonaqueous reactive expansive polymers in sand and gravel media under dynamic water conditions were carried out using a homemade experimental device. The effects of grouting parameters such as dynamic pump pressure, mass fractal dimension, and grouting volume on the effective diffusion length and water plugging rate of the slurry were revealed. The results show that (1) the diffusion behaviour of nonaqueous reactive expansive polymers in sand and gravel media can be summarized as edge dispersion, downstream diffusion, and expansion diffusion. (2) The diffusion consolidated bodies of nonaqueous reactive expansive polymers mostly exhibit a hemispherical or columnar shape with a wide top and a narrow bottom. (3) The greater the pressure of the moving water pump is, the smaller the effective diffusion length of the slurry. Under the same grouting volume, with increasing mass fractal dimension, the effective diffusion length of the slurry first increases and then decreases. (4) Under the conditions of high dynamic water pump pressure and low mass fractal dimension, increasing the grouting volume has a better water plugging effect.

Laboratory Study of Grouting Method to Improve Loose Sand Against Liquefaction

Liquefaction is a phenomenon when soil behaves like liquid during earthquake, and only occurs in saturated loose fine sand with grain size ranging from 0.2 to 0.02 mm. Liquefaction can be devastating, causing failure and deformation to buildings, roads, and bridges. Thus, research study on the application of grouting method for improving liquefiable fine sand in the laboratory is carried out. Grouting is a soil improvement method that injects cementing agent into a soil mass. After the grout has solidified, the soil density and consistency of the soil will improve. This research proves, mathematically and experimentally, that grouting can improve the density and consistency of liquefiable sand, thus reducing the liquefaction potential. Grouting liquefiable saturated sand basically compacts the soil, leading to consolidation as soil pore-water is dissipated during the grouting process. It is found that the volume of grout per unit volume of soil mass treated is directly proportional with the reduction of void ratio and increase in soil density.

Research on the influence of clay shock on inert slurry in shield-tunneling construction

Shield-out synchronous grouting is a new technology used to fill temporarily shield-out spaces between the strata and the shield when creating subterraneous tunnels. The grouting materials are called ‘clay shock’, which is soft, plastic, sticky and easily dispersed by using a pressurized jet. This study analyzes the mixing process of clay shock and backfill grouting material (inert slurry) and investigates the influence of clay shock on the inert slurry through laboratory testing. The findings show that the fluidity and bleeding rate of the inert slurry continuously decrease with the clay shock volume. The unconfined compressive strength and flexural strength of the inert slurry increase initially before decreasing with the clay shock volume ratio. The X-ray diffraction and scanning electron microscopy results reveal that the alkalinity of the clay shock initiates an alkali excitation reaction, which generates more gelling products and increases the strength of the inert slurry. Excessive clay shock causes the inert slurry to retain a loose and porous structure, which then decreases its strength. To ensure the effect of the inert slurry on settlement control, the grouting volume of the clay shock should not exceed one-fourth of the inert slurry volume.

Temperature dependency analysis of the fracture characteristics of semi-flexible pavement (SFP) mixtures using acoustic emission technique

ABSTRACT The poor cracking resistance of Semi-Flexible Pavement (SFP) mixture has limited its wider application. Particularly, the dual skeletal interlocking structure makes its damage process complicated. Its fracture process is expected to change with aggregate gradation and temperature, but the relevant knowledge is very limited. Thus, this study aims to investigate the effects of the two factors on the fracture characteristics of SFP using the acoustic emission (AE) technique and X-ray computed tomography (CT) approach. SFP specimens with three gradations (the target cement grout volume is 22%, 25% and 30%, respectively) were fabricated and subjected to the split tensile tests at three different temperatures (−10°C, 10°C and 25°C). Machine learning-based techniques were applied to analyze the AE signals to improve the understanding of the mesoscale damage process. Although the analysis of macro mechanical parameters showed the diminishing effect of temperature dependency on the fracture process with an increase in cement grout volume, the effect was found to be still significant based on the mesoscale analysis. Besides, it was found that the damage process transferred from the main crack going through cement to distributed meso-cracks in asphalt and cement with the temperature increase.

Performance evaluation of post-grouting for bored piles installed in inhomogeneous gravel pebble stratum overlaid by deep and soft soil layers

ABSTRACT To study the behaviours of post-grouted piles installed in an uneven pebble bearing layer overlaid deep and soft soil layer in Wenzhou, China, static loading field tests of three bored post-grouted piles were conducted, considering the key design parameters of post-grouting including the grout volume, grout pressure, and bearing capacity. According to the on-site geological conditions in the region, the theoretical values were calculated through applying different calculation equations for these three parameters, and the actual values obtained from the field tests were investigated to assess the improvement effect of load-bearing performance of grouted piles installed in these geological conditions as an extremely uneven pebble-bearing layer overlaid by the deep and soft soil layer. The calculation equations of key design parameters of post-grouting in this type of soil layers were then proposed. This study could provide a reference to evaluate the performance of post-grouted piles under various grouting parameters in analogical soil layers.

Grouting mechanism and experimental study of goaf considering filtration effect.

The filtration effect significantly affects the gangue slurry velocity and concentration, making it difficult to evaluate the gangue slurry diffusion range. Based on the Darcy seepage law, a seepage theoretical calculation model is established considering the filtration time and space effect. And the "water-cement ratio change matrix" in the seepage process of coal gangue slurry is deduced, revealing the basic mechanism of the porous media filtration effect, and the water-cement ratio gradually increases in the seepage process of gangue slurry. The visual test platform for slurry diffusion in goaf was independently developed for testing. The active heating optical fiber method (AHFO) was used to monitor the flow and diffusion of coal gangue slurry in the collapse zone of goaf, and the gravity gradient and water cement ratio of slurry in goaf were measured. The law of particle sedimentation in the gangue slurry flow process under the filtration effect was revealed, and engineering verification was carried out. The results show that the average slope of the gangue slurry in the gangue accumulation is 6.34%, and the overall flow law of the gangue slurry in the goaf is the first longitudinal expansion and then transverse diffusion. The water-cement ratio near the grouting mouth is smaller than the initial water-cement ratio, the near-end water-cement ratio is smaller, and the far-end water-cement ratio is larger. During on-site filling, the accumulated grouting volume of a single hole is 700 m3, and the gangue slurry diffusion distance is greater than 45m, indicating that the gangue slurry has good fluidity.

Recovery of longitudinal deformational performance of shield tunnel lining by soil Grouting: A case study in Shanghai

This paper presents a case study introducing the effect of soil grouting conducted to repair the longitudinal performance of shield tunnel in Shanghai. The maximum of cumulative settlement of the shield tunnel was approximately 15 mm with an averaged increasing rate as high as 0.50 mm/d caused by a new tunneling project underneath. The grouting reinforcement for soils under the invert of tunnel was thus carried out in the distorted section. A full process of deformational responses in terms of settlement and horizontal convergence to the grouting was measured to analyze the influence of grouting on performance recovery in the longitudinal direction. Volume-based grouting efficiency was defined for evaluating the contribution of grouting to structural deformation recovery. The results showed that the settlement is reduced linearly with the increasing of grouting volume. However, horizontal convergence increased during the grouting process and the maximum convergence increment was about 63 % of the magnitude of settlement reduction. Meanwhile, grouting efficiency was found to be relatively low. An average of 9.03 % of the grout volume is contributed to the recovery of settlement trough, while 2.75 % acted on the increase of convergence. Besides, continuous grouting can effectively recover tunnel settlement and remain a safe state.

Effects of soil unloading and grouting on the vertical bearing mechanism for compressive piles

The present study conducts a series of model cast-in-place piles tests to analyze the vertical bearing characteristics and the grout returned diffusion mechanism along the pile shaft of tip post-grouting piles with different grouting and pile shaft soil unloading conditions. The model test results show that the pile tip post-grouting technology can improve the weak difference in the bearing characteristics and axial force distribution of the pile foundation caused by pile shaft soil unloading. The pile shaft resistance can be improved by the returned grout in the pile shaft. The pile shaft resistance will mainly bear the pile top load when the pile top load and the grouting volume are relatively small, and the pile tip resistance will mainly bear the pile top load with the increases of the pile top load and the grouting volume. The grouting return height increases with the increase in pile shaft soil unloading degree, and the analyzed values of the grouting returned height based on the pile bearing characteristic results are close to the measured values. The grouting diffusion mechanism of the cement on the pile tip and pile shaft soil during the pile tip post-grouting process is revealed.