Soil Grouting Research Articles

Field behavior of pre-bored grouted planted nodular pile embedded in deep clayey soil

This paper presents the results of field tests performed to investigate the behavior of pre-bored grouted planted nodular (PGPN) pile embedded in deep clayey soil. The test piles were all instrumented to measure the shaft and tip resistance and to determine the load transfer along the pile shaft. The test results show that the displacement necessary to fully mobilize the shaft resistance of PGPN pile is in the range of 1.83–3.32% D (D is pile diameter), and that the ultimate skin frictions of grout–soil interface of different soil layers are larger than the conventional proposed ultimate skin frictions for non-displacement piles. Furthermore, the pile tip resistance accounts for about 16% of the total applied pile head load corresponding to a pile head displacement of 0.1 D, and the pile tip resistance continues to increase after tip displacement reaches 5% of pile tip diameter.

Time-dependent empirical model for fracture propagation in soil grouting

The fracture grouting method has been widely adopted to strengthen weak rock masses around tunnels and other underground constructions. However, the current understanding of fracture mechanism, especially in relation to the fracture propagation process, is still limited. This paper presents a time-dependent empirical model to describe the fracture propagation process in soil, and to show its change caused by increase of grout injections, which can also be used to obtain empirical solutions for the fracture thickness and grout driving pressure in two grout injections. The relation between grout behavior and soil reaction is modelled through a modified compression and recompression soil model. In case of two grout injections with the same injection point, a novel fracture geometry schematization has been developed, which can be represented as a radial plane with the injection point at the center. A series of numerical examples show that the grout driving pressure in the second injection can be 5–10 times larger than that in the first injection, while the fracture thickness can be 36–42% smaller. Finally, the fracture grouting test is performed to verify the suitability of empirical model to predict the fracture thickness and grout driving pressure in two injections. Comparison of theoretical values and experimental values shows that they match reasonably well with each other.

Micromechanical investigation of grouting in soils

Grouting and jet grouting are geotechnical consolidation techniques commonly employed to improve the mechanical behaviour of soils. Although these techniques are common, the micromechanical processes taking place at the local level are not yet totally understood and modelled. In this work, such a problem has been approached from a micromechanical perspective via the discrete element method by considering the local interaction among soil grains and pseudo-fluid particles. Homogeneous representative elementary volumes of a virtual analogue of silica sand have been first generated and tiny rigid frictionless particles have been subsequently injected through them, to simulate the grouting in granular materials. Various injection pressures, initial soil pressures and initial soil densities have been considered. The different diffusion patterns, the flow rate, the consequent increase in local stresses and the consequent reduction in local porosity have been discussed. To overcome the DEM computational restrictions and to speed up the injection simulations, a novel procedure based on the replication of pre-equilibrated cells has been adapted for both the initialization and injection phase. Finally, a qualitative laboratory-scale pressure grouting test has been reproduced to validate the results.

Analysis of the influence of soft soil grouting on the metro tunnel based on field measurement

Purpose This paper aims to analyse the effect of soft soil grouting on the deformation of the closed shield tunnel with the measured data. Design/methodology/approach Combining the measured data of vertical, horizontal and convergence deformation of the adjacent tunnel during the grouting construction in foundation pit engineering, the influence of grouting on metro tunnel in soft soil area is analyzed. Findings The researches indicate that early grouting has the main effect on the horizontal displacement of the tunnel; Due to the disturbing effect of the uninterrupted grouting construction on the soil and the transfer pressure of the rheological soil to the bottom of the tunnel, the tunnel is obviously lifted; And the convergence deformation of the tunnel increases caused by the overburden pressure in the vertical direction, so that the tunnel appears the phenomenon of staggered seam, large opening of bolted joint, damaged segment even leakage of water. Originality/value The study based on the field monitoring data is rarely reported, especially the topic about inadvertent grouting in soft soil area is likely to cause severe deformation of adjacent metro tunnel.

Experimental Investigation of Bond Stress and Creep Displacements of GFRP Soil Nails Simulated in a Soil Box

Fiber-reinforced polymer bars, as an alternative for steel bars, are widely used to overcome the corrosion problem especially under severe environmental conditions. In the present research, the soil nail system was physically modeled in the laboratory. Since bond stress and creep displacements of the GFRP nails are not well understood yet, the nail–grout and grout–soil interfaces were experimentally investigated simultaneously in a soil box. In the first step, the bond stress of the GFRP soil nails was studied through pullout tests. Subsequently, experimental creep tests were carried out under sustained loads which were equal to a fraction of ultimate pullout load. Furthermore, the effect of soil density and surcharge pressure on bond stress of both interfaces was evaluated. In addition, the ultimate bond strength of the nail–grout interface was measured by physical tests, and the grout could not move. Finally, the dependency of creep displacements on different load ratios and variable surcharge pressures was explored. The results clearly showed that the ultimate pullout load of the steel nail–grout interface with no surrounding soil was more than that of GFRP. The grout–soil bond stress was affected by the variation of soil density more than nail–grout and an almost linear relationship between soil unit weight and bond stress was observed at both the interfaces. Nevertheless, the increment rate of bond stress decreased with the growth in surcharge pressure at both interfaces. Moreover, creep tests displayed an interdependency of creep displacements at the interfaces and rate of reduction of creep displacements with the decrease in the surcharge pressure increment.

Investigation of hydrogeomechanical parameters of loess massifs in conditions of technogenic underflooding and development of technical recommendations for strengthening of bases of foundations

Based on the analysis of actual data and the results of numerical modeling, dependencies of deformations of the investigated residential complex due to technogenic moistening of a loess massif of soils are investigated. It was established that a dynamics of subsidence of bench marks in time is closely correlated with a moistening mode. In order to form a picture of dynamics of development of moistening phases of the massif and a quantitative estimation of main factors of their formation, a numerical model of the loess massif was built, based on the finite element approximation of the section of built-up area of the residential complex. Stability of a soil massif was estimated by the character of development of plastic deformation zones. Analysis of a stress-strain state of a rock massif indicated that water-saturated soils are partially in a state of plastic flow in a base. The development of shear deformations is most characteristic within a zone of the main moistening, as well as a boundary of its front. Development of rupture disturbances at the edge of the contour of buildings corresponds with the formation of tear cracks. An intensification of subsidence of buildings with simultaneous frontal and subvertical technogenic moistening of loess soils can be noted. Model estimations of a stress-strain state of the pile foundation, considering the uneven subsidence that occurred along the perimeter of residential buildings, show that the elastic mode of their deformation has not been exhausted. Options of redistribution of loads from residential sections onto an additional pile field, regulated base moistening and grouting of soils are considered as engineering measures to prevent further deformation of the residential complex. Stabilization of a soil base by means of high-pressure cementation is the most acceptable in the present conditions. Technological scheme of cementation of the soil base is recommended, as well as measures after the base stabilization, such as monitoring of further deformations of the complex itself and parking structures, and possibilities of constructing auxiliary drainage.

Influence of Grouting Pressure on Bearing Capacity of Pile Foundation Under the Sandy Soil

The aim of the paper is to investigate the increase of bearing capacity of pile after grouting. In this paper, through the soil grouting reinforcement experiment and the numerical simulation of the bearing capacity of the pile, the increase of pile bearing capacity was investigated and compared with the standard method. Thus The relationship between grouting pressure, cohesion force and internal friction angle was obtained through grouting test. Grouting pressure has a great influence on cohesion force and a slight influence on internal friction angle. The lifting capacity of pile foundation obtained by numerical simulation is close to that of pile foundation obtained by formula. It is feasible to calculate the lifting range of bearing capacity of pile foundation by standard method.

Fracture grouting and geonails for soft soil tunnelling

ABSTRACTTo stabilise the tunnel faces and slopes in soft clay for the Airport Link construction in Australia, fracture grouting and glass fibre-reinforced plastic (GFRP) soil nails are proposed for the soil improvement as well as ease of handling. The compensation caused by the fracture grouting and the gain in strength due to consolidation as well as the geonail have stabilised the soft clay during construction. Only a small amount of ground settlement during soft clay box-jacking operation is generated so that the railway traffic above the embankment can be maintained without interference. The design method of the fracture grouting ground improvement study for this difficult project is discussed in this paper. Extensive laboratory and field tests were employed to verify the design assumptions and to fine-tune the ground improvement studies. The success of this project in poor ground conditions results from combined efforts of extensive field tests, an improved ground improvement design method and a realistic numerical analysis to assess the unstable/highly stressed zones for the placement of soil reinforcement.

Bearing characteristics of large-diameter hollow composite pile

Large-diameter hollow composite pile is a new type of pile which is composed of hollow pile, cement mixing pile around the pile and grouting soil around the pile. In order to analyze the influence degree of soil grouting and cement mixing pile around the pile on the improvement of pile foundation bearing capacity, the vertical and horizontal load-bearing characteristics of large-diameter hollow composite pile are studied by numerical simulation, and the structural practicability of the new foundation is analyzed. Research shows that grouting around piles and grouting around piles + cement mixing piles have obvious effects on the improvement of pile bearing capacity, the vertical bearing capacity increased is by 7.4% and 12.1% respectively, while the horizontal bearing capacity is increased by 7.2% and 14.4% respectively. Compared with solid group piles of the same pile side area, the bearing capacity of large-diameter hollow composite pile foundation is increased by 19.1%. The research results can provide theoretical basis and technical support for the design and construction of large-diameter hollow composite pile foundation.

Properties and performance of a high volume fly ash grout

This study investigated the penetrability of high volume fly ash cement suspensions prepared with and without superplasticizer into sandy soil having different relative densities with 30%, 60%, 73%, and 83% through permeation grouting. Class C fly ash was used due to its pozzolanic activity and fineness. Due to engineering characteristics and cost, cementitious grouts are the most commonly used grout in both waterproofing and ground strengthening. Fly ash-cement grouts have relatively constant and low viscosity values for a reasonable period after preparation, exhibit limited or negligible bleed capacity and set and develop satisfactory strength within a relatively short period. Modeling of grouting of soil was done in laboratory and improvements in physical and mechanical properties of grouted soil were analyzed. Unconfined compressive strength, shear strength and permeability characteristics of grouted soil were studied as a result. Unconfined compressive strength values of grouted sand with high volume fly ash ranged between 410 and 1107 kPa. Morover, cohesion values were comparable to microfine cement grouting ranging from 373 to 511 kPa. Furthermore, permeability values were also approximately equal to the permeability of impervious liners, which is around 1 × 10−7 cm/s. The findings support the applicability of grouting in different applications.

Calculation of colloids filtration in a porous medium

Construction of underground storage facilities for hazardous radioactive waste requires soil grouting to prevent the penetration of groundwater. Modern technologies of grouting use a liquid-type colloidal silica grout which is injected in a porous soil and forms a protective waterproof layer after solidification. Colloids filtration in a porous medium is an important problem of underground hydromechanics.The purpose of the study is the numerical solution of the filtration problem of suspensions and colloids in a porous medium. A fluid with fine particles is injected into an empty porous medium. Suspended particles are transported by the fluid flow in a porous medium and partially get stuck in the pores. Calculation of the suspended and retained particles concentrations, depending on time and coordinate, is the theoretical basis of the soil grouting technology.The one-dimensional problem of deep bed filtration with suspended solid particles in a porous medium for variable porosity and permeability is solved by modified finite difference methods. The use of standard methods for solving the problem is impossible because of the solution discontinuity on the mobile boundary of two-phases. To calculate the global solution near the line of discontinuity and away from it, the counter-current scheme, the Lax-Wendroff scheme and the Total Variation Diminishing finite difference scheme are used. To eliminate the effects of dissipation and dispersion in the TVD-scheme various functions-delimiters are used.The result of this work is the numerical solution of the nonlinear filtration problem in a porous medium with size-exclusion mechanism of particles retention. The curvilinear two-phase boundary is calculated. A comparison of obtained numerical solutions using different methods of constructing difference schemes is provided. The graphs of suspended particles concentrations are constructed in dependence on time and coordinates.The comparison of the numerical solutions obtained by different finite-difference methods makes it possible to choose the best way for solving the filtration problem. The counter-current scheme strongly smoothes out the solution on the line of fracture. Using a non-monotonic Lax-Wendroff scheme, a solution with unnatural oscillations near the two-phase boundary is obtained. To calculate the filtration problem, TVD-schemes are the most acceptable. The best result is obtained when using the TVD-scheme with the function-delimiter min2.

Asymptotic model of size-exclusion grouting

In the construction of foundations of buildings and structures on fragile ground, various technologies of soil grouting are used. When pouring fine-grained concrete into the porous soil, the concrete grains are filtered in the pores of the soil. The filtration process depends on the ratio of the pore sizes of the soil and the solid particles of the injected concrete mortar.Injection of a carrier fluid with small solid particles in a porous medium forms a dynamic concentrations front of suspended and retained particles, separating the suspended particles and the hollow part of the porous frame. The purpose of the study is to construct and calculate an asymptotic model near the concentrations front for the filtration of monodisperse suspension in a porous medium with size-exclusion mechanism of particles retention.The classical mathematical model for one-dimensional filtration of suspensions and colloids in a porous medium is based on the geometric ratio of the particles and pores sizes: the particles freely pass through the large pores and get stuck in the pore throats with sizes smaller than the particles diameter. The model is determined by a system of two quasilinear first-order partial differential equations with the gap between boundary and initial conditions. To construct an asymptotic expansion in the vicinity of the concentrations front, a special small parameter is used that specifies the distance to the front. This parameter provides direct determination of the asymptotic terms from the recurrent system of ordinary linear differential equations of the first order.Near the concentrations front of the suspended and retained particles, a nonlinear high-order asymptotics is constructed for the filtration problem of solid particles transported by a carrier fluid in a porous medium. The obtained solution is zero before the front and nonzero behind the front. Approbation of the asymptotic expansion is carried out. It is shown that, for a linear blocking filtration coefficient, the asymptotics coincides with the exact solution.The asymptotic model of deep bed filtration makes it possible to obtain exact formulas for the high-order asymptotic expansion near the dynamic concentrations front of suspended and retained particles. The asymptotics improves the ability to fine-tune the filtration model depending on the properties of the porous soil and the grout.

Modelling of particles retention in a porous soil

Construction of foundations and underground structures requires grouting the soil for groundwater protection. To select the technology of soil grouting and the type of grout, it is necessary to calculate the suspended particles retention for the filtration of bentonite or cement-based suspension in a porous soil in dependence of sizes of the soil pores and the grains of the injected mortar. The study of transport and retention of solid particles in the complex structure of a porous medium makes it possible to calculate the strength and impermeability of a grouted foundation at the stage of pre-construction preparation.The solid particles retention in the nonlinear process of deep bed filtration of a suspension in a porous medium is considered. It is assumed that the retained particles can not be detached from the frame of porous medium by a fluid flow or suspended particles. The purpose of the study is to calculate the dynamics of deposit formation for different types of variable filtration coefficients with the predominance of the size-exclusion mechanism of particles capture.The mathematical model of filtration is the system of mass transfer equation and the kinetic equation of deposit rate with the conditions of injection of a constant concentration suspension into an empty porous medium. In this paper an exact solution of the problem at the inlet of a porous medium is constructed. The dynamics of retained particles growth is studied by numerical modeling method, depending on the type of blocking filtration coefficient.The dependence of retained particles concentration on time at the inlet of a porous medium for various blocking filtration coefficients was obtained. Plots of the dependence of the deposit concentration on time for smooth and non-smooth filtration coefficients are constructed.When reducing the number of free pores of small sizes, the filtration rate slows down. It is shown that slowing down the filtration process and the growth rate of the deposit are determined by the multiplicity of the root of the blocking filtration coefficient. Depending on the type of filtration coefficient, the process of retention of solid particles in a porous medium can last indefinitely, or it may cease after some time with complete blocking of small pores by retained particles. The limiting time for the end of the filtration is given by a compact analytical formula.

Investigating performance of micropiled raft in foundation of power transmission line towers in cohesive soil: experimental and numerical study

This paper captures the behavior of micropiled rafts in power transmission line tower foundations in cohesive soil, concentrating on their uplift performance whether due to the tower position along the line or under wind loading conditions. In this regard, first a number of micropiles were driven into the ground of a project site at the ParehSar power plant, Gilan, Iran. Compression and uplift loading tests were conducted according to relevant standards. On the basis of the field data, a three-dimensional finite element model was developed and subsequently calibrated and verified. The behavior of micropiled rafts subjected to uplift, which is a typical type of loading in foundations of 230 kV four-circuit lattice towers, was then studied by means of this model in terms of a wide-ranging parametric study. In the sensitivity analyses, the impacts of various parameters, such as micropile spacing-to-diameter (s/d) and length-to-diameter (l/d) ratios along with undrained shear strength of the soil, on the uplift capacity of an individual micropile within and out of the group were investigated. Furthermore, interaction factors were computed based on diverse values for undrained shear strength of the soil, s/d ratio, l/d ratio, and grout–soil adhesion. From design and analysis perspectives, the finite element method (FEM) outputs revealed that the efficiency coefficient of micropiled rafts during uplift can be considered equal to one. Moreover, it was found that not only does the behavior of micropiles affect the neighboring micropiles immediately adjacent to the loaded one, but it also influences those in further rows, the result of which would be considering their significance as well.

The differences between soil grouting with cement slurry and cement-water glass slurry

Cement slurry and cement-water glass slurry are the most widely applied for soil grouting reinforcement project. The viscosity change of cement slurry is negligible during grouting period and presumed to be time-independent while the viscosity of cement-water glass slurry increases with time quickly and is presumed to be time-dependent. Due to the significantly rheology differences between them, the grouting quality and the increasing characteristics of grouting parameters may be different, such as grouting pressure, grouting surrounding rock pressure, i.e., the change of surrounding rock pressure deduced by grouting pressure. Those are main factors for grouting design. In this paper, a large-scale 3D grouting simulation device was developed to simulate the surrounding curtain grouting for a tunnel. Two series of surrounding curtain grouting experiments under different geo-stress of 100 kPa, 150 kPa and 200 kPa were performed. The overload test on tunnel was performed to evaluate grouting effect of all surrounding curtain grouting experiments. In the present results, before 240 seconds, the grouting pressure increases slowly for both slurries; after 240 seconds the increase rate of grouting pressure for cement-water glass slurry increases quickly while that for cement slurry remains roughly constant. The increasing trend of grouting pressure for cement-water glass is similar to its viscosity. The setting time of cement-water glass slurry obtained from laboratory test is less than that in practical grouting where grout slurry solidifies in soil. The grouting effect of cement-water glass slurry is better than that of cement slurry and the grouting quality decreases with initial pressure.

Comparative Study of Soil Grouting with Cement Slurry and Cement‐Sodium Silicate Slurry

Cement slurry and cement‐sodium silicate slurry are most widely applied for soil grouting reinforcement project. The viscosity change of cement slurry is negligible during grouting period and presumed to be time independent, while the viscosity of cement‐sodium silicate slurry increases with time quickly and is presumed to be time dependent. Due to the significant rheological differences between them, the grouting quality and the increasing characteristics of grouting parameters may be different. Those are main factors for grouting design. In this paper, a large‐scale 3D grouting simulation device was developed to simulate the surrounding curtain grouting for a tunnel. Two series of surrounding curtain grouting experiments under different initial pressures of 100 kPa, 150 kPa, and 200 kPa were performed. The overload test on the tunnel was performed to evaluate the grouting quality of all surrounding curtain grouting experiments. The results show that the increasing trend of grouting pressure for cement‐sodium silicate is similar to its viscosity; the setting time of cement‐sodium silicate slurry obtained from the laboratory test is less than that in the practical grouting environment where grout slurry solidifies in soil; the grouting quality of cement‐sodium silicate slurry is better than cement slurry, and the grouting quality decreases with initial pressure.

Estimation of borehole heat exchanger thermal properties

An important issue in the design of installations with borehole heat exchangers (BHE) is knowledge of the thermo-physical properties of the grouting material and soil. The objectives of this work is to estimate the thermal conductivity and specific heat of the grouting material and the soil. The estimated values were determined on the basis of two numerical heat transport models in the borehole and using the results of the small sandbox experiment. The design of experiment technique (DOE) and the response surface methodology (RSM) were used to achieve the aim of this work. Numerical calculations were carried out with the use of the new finite element with multiple degrees of freedom (MDF) and a quasi-3D model in ANSYS package. The estimation requires minimization of four output parameters (quality criteria), and therefore it is a multiple-objectives optimization problem. Based on the DOE, RSM and multiple-objective optimization the material properties of BHE and soil was determined. For both models the discrepancies Y1P1 are below 4 %, Y2P1 are below 11.5%, Y1P2 are below 6.5 % and Y2P2 are below 11.5 %. The average discrepancies below 5 % based on the verification measurements with different operating parameters was obtained. It is noteworthy that for the two different models the same values of the estimated parameters were obtained.

Penetrability prediction of microfine cement grout in granular soil using Artificial Intelligence techniques

In connection to permeation grouting present study is aimed to investigate the penetrability of microfine cement (MC) grout in granular soil. Series of laboratory based sand column grouting tests were undertaken to characterize the penetrability of MC grout in granular soil in terms of rheological properties of grout suspension (i.e. yield stress, τ0 and plastic viscosity, µ), properties pertinent to sand and grout material such as fine sand content (FC), relative density of sand (RD) and uniformity coefficient of sand (Cu) and groutability ratio (N2) and grouting procedure (i.e. grouting pressure, P), using permeation grouting technique. Ten (10) different sand types having d10 ranging from 0.17 mm to 2.53 mm and Cu ranging from 1.35 to 5.76 were grouted in laboratory with MC grout suspensions under two different relative densities (i.e. 30% and 70%). MC grout suspensions were prepared with four different water to cement (w/c) ratios viz. 0.8, 1, 2 and 3. Rheological tests of the MC grout suspensions prepared with different w/c ratios were performed to evaluate the flow properties (τ0 and µ). Subsequently, artificial neural network (ANN) and support vector machine (SVM) based penetrability prediction models were developed to correlate penetrability with τ0, µ, FC, RD, Cu, N2 and P. Sensitivity analysis and neural interpretation diagram (NID) was employed to identify the key variables in penetrability prediction, to measure its effect and to explain and extract understandable knowledge from the proposed model.

Evaluation of interface shear behavior of GFRP soil nails with a strain-transfer model and distributed fiber-optic sensors

A glass fiber reinforced polymer (GFRP) material is a newly developed material for slope reinforcement. In this study, distributed optical fiber sensors are developed to characterize the interface shear stress–strain behavior in GFRP soil nails with a strain-transfer model. The GFRP bar with a diameter of 40 mm was used as a reinforcing element in a soil slope subjected to excavations. A newly distributed fiber optic sensors are developed to measure the axial strains of the GFRP reinforcement which was then inserted into a drilled hole together with pressure grouting. The calibration of distributed fiber optic sensors indicated that the strains along the GFRP bar can be accurately measured by the distributed sensors. An analytical strain-transfer model is developed and then verified with a finite element model. The comparisons indicate that the strain-transfer model could be able to obtain the shear strain and stress at the cement grout–soil interface from arbitrary strain of the GFRP bar. Finally, a field project study is conducted for the condition assessment of a GFRP soil nail with the interface shear stress at different excavation depths. The potential failure surface is identified at the position where the maximum shear stress occurs, that is, at the point around 4.5 m away from the soil nail head. Results in terms of the shear stress are able to detect the active and passive zones of the soil nail. A further analysis indicates that the health condition of the GFRP soil nail can be determined with the distributed fiber sensors and strain-transfer model.

Discussion: Ground response and grout distribution by field soil grouting

Discussion: Ground response and grout distribution by field soil grouting