Polyurethane Grout Research Articles

Experimental study on the diffusion characteristics of polyurethane grout in a fracture

Although polyurethane grouting has been widely used in fractured rock masses, the understanding of polyurethane diffusion characteristics still needs to be enhanced significantly. To analyse the diffusion mechanism of the polyurethane grout in the fracture, physical simulation experiments were conducted using a self-designed device. Additionally, the influence of grouting quantity on the grout diffusion distance and pressure distribution was investigated. The results indicated that the diffusion radius and pressure field increased with the increase in grouting quantity. Furthermore, the pressure growth rate and grout diffusion rate during the early self-expansion stage is directly proportional to the amount of polyurethane grout injected. However, the change in grout pressure is not synchronised with that of the diffusion radius. Hence, a hysteresis effect was observed for the pressure field change. Additionally, the grout pressure, which was not distributed evenly, decreased along the diffusion radius as it moved away from the grout hole. Furthermore, we derived the relationship between maximum diffusion radius and grouting quantity. Therefore, this study provides a better understanding of the diffusion law of polyurethane grouting in fractured rock masses.

Track settlement restoration of ballastless high-speed railway using polyurethane grouting: Full-scale model testing

Excessive uneven settlements of railway subgrades will reduce the durability of ballastless slab track and jeopardize the train operation safety. In this paper, a technology by injecting polyurethane materials beneath the slab track to uniformly lift the track level is introduced to eliminate track uneven settlement and to ensure its good performance. The mechanical properties and long-term durability of track/roadbed systems that have been rehabilitated by polyurethane grouting are presented. The cyclic uniaxial loading test shows that the polyurethane material has good stability and durability after 3,400,000 cycles of loads; full-scale ballastless track model test shows that the stiffness of track-subgrade system initially decreases by 20% after grouting, resulting in an increase in the track dynamic responses, and after 790,000 cycles of train loads, the stiffness of the grouted subgrade gradually increases while the accumulative settlement is less than 3 mm for maximum 46.12 mm uplift, indicating that the polyurethane-grouted subgrade has good dynamic stability under long-term train loads. Afterwards, this technology was successfully applied in restoring track geometries in an uneven settlement zone of a high-speed railway line on the east coast of China. In-situ tests show that the polyurethane grouting significantly improves the track geometries and control the post settlements after grouting. According to the lab and in-situ tests, it is demonstrated that the polyurethane grouting technology can effectively restore ballastless track uneven settlements and provides adequate long-term durability under moving train loads.

A Field Experimental Study on the Diffusion Behavior of Expanding Polymer Grouting Material in Soil

The diffusion behavior of expanding polyurethane foam, which is widely used in soil improvement, foundation remediation, and road maintenance, was investigated. This study is the first step towards the ultimate aim of examining the feasibility of using polyurethane foam for constructing a vertical impervious curtain in soil dams or dikes. Using a hole-sealing grouting method, experimental grout injection tests were performed in situ on a type of foaming polyurethane grout, comprised of two components. The results reveal that sheet fracturing diffusion was evident in the foaming polyurethane grout, eventually forming wedge-shaped segments in the generated cracks. Moreover, the direction along which the grout fractures the soil exhibits some uncertainty due to the unevenness in the soils and the random distribution of stress inside the dam. The test results show that for the purpose of constructing a continuous cut-off wall in the dam by injecting polymer grouts, some effective measures should be taken to guarantee that the polymers fracture the soil in the required direction, or axis of the dam or dike, and that the final solidified segments overlap one other.

The study on compressive mechanical properties of rigid polyurethane grout materials with different densities

The rigid polyurethane grout materials with different densities show elastoplastic or atypical brittle characteristic, which will significantly affect their performance. To clarify these mechanical characteristics of polyurethane foams with different densities, uniaxial compression tests and SEM experiments were carried out. To further describe these different mechanical characteristics quantitatively, two integral models based on superposition and segmentation methods were proposed, respectively. Moreover, two simplified integral models were developed to make models easy to be applied. Through error analysis, it is found that the average errors of integral models are less than 0.02 MPa and the average errors of simplified integral models are less than 0.035 MPa. The integral models are accurate while the parameters of simplified integral models are less.

Preparation and performance of the modified high-strength/high-modulus polyvinyl alcohol fiber/polyurethane grouting materials

In this study, modified polyvinyl alcohol fiber (MPVA) filled polyurethane (MPVA/PU) grouting materials with high interfacial bonding strength were prepared. Firstly, the high-strength/high-modulus PVA fibers were modified by γ-aminopropyl triethoxysilane (APTES) and diphenyl-methane-diisocyanate (MDI) respectively. The chemical structure, surface morphology and hydrophilicity were characterized by FT-IR, XPS, SEM and contact angle analysis. Second, the performance of PU mixed with different dosages of modified PVA fibers as the grouting material was studied. The results showed that mechanical properties and hot air aging resistance of the MPVA/PU composite weresignificantly increased compared with pure PU. In particular, it also can be found that modified PVA fiber bring better interface adhesion, especially, when the dosage is 0.1%, the best overall performance of MPVA/PU can be achieved. SEM analysis demonstrated that the interface adhesion between modified PVA fiber and PU was obviously improved.

Effects of fracture grouting with sodium hydroxide during electro-osmosis on clay

ABSTRACTElectro-osmosis is a foundation treatment method for clay that is not widely used because of its nonuniform consolidation effect and high cost. To overcome these limitations, this study investigates fracture grouting. To determine the optimal grouting method, anode grouting, polyurethane grouting, and fracture grouting were first compared in one-dimensional electro-osmosis consolidation tests using self-made model boxes under an equal electric potential gradient, and then different solution concentrations were tested. By comparing the current, drainage rate, and coefficient of energy consumption during the electro-osmosis process, as well as moisture content, electrical conductivity, and shear strength after the tests, the moisture and shear strength of clay after electro-osmosis were found to be significantly improved by adding chemical reagents at the fracture. In addition, the optimum concentration of fracture grouting was determined to be 1.5%, and the shear strength after testing of clay that had been treated with sodium hydroxide was found to be higher than that of the control group. However, the effects of fracture grouting in the early stage were clearer than the effects of fracture grouting at later stages.

Strength for Modified Polyurethane with Modified Sand

The Polyurethane grout is an effective method used for improving the soils stabilization without disturbing the original soil structure, which is workable for construction and enhances the performance of soil compressive strength. In order to study the effect temperature, acetone rate, sodium silicate rate, mass fractal dimension of particle, and particle shape on the compressive strength. In order to lighten the workload considerably, the central composite design under response surface methodology was utilized. In this study, different content percentages of PU were injected into the modified sand and the compressive strength of specimens from the modified sand injected was determined by conducting the unconfined compression test. The results indicated that the existence of temperature, beyond which the strength has no change with the increase of temperature. And the strength of specimen increases with the increase of acetone mass ratio, over a critical value, it decreases. And that the strength of the specimen increases with sodium silicate ratio until a critical value (6%), beyond which it decreases slightly. And also the comprehensive strength of specimen is well correlated to the fractal dimension and shape of particles.

Experiment and modeling for compressive strength of polyurethane grout materials

This study conducted comprehensive experimental and modeling investigations on compressive properties of polyurethane grout materials with the density of 0.08-0.5 g·cm-3.SEM and uniaxial compression tests were applied to specimens with varied density.Parameters obtained from SEM images were employed to predict compressive strength.It is found that foams in higher density specimens are spheres owning less contact area,which ensures the system stability based on the minimum energy principle.While majority foams in lower density specimen are polyhedrons and their contact area is larger.The uniaxial compression can be divided into elastic (strain less than 5%),yield (strain from 5% to 50%) and densification (strain higher than 50%) stages.In elastic stage,strain of higher density specimen develops faster with normalized stress,while the corresponding stress at yield stage can be viewed as compressive strength and develops with density,and in densification stage higher density specimens are characterized with brittle failure.Gibson-Ashby model based on geometric parameters of foams obtained from SEM image can be used to predict the compressive strength,and materials with varied density characterized with different strength can be applied in infrastructure maintenance.

Strength Characteristics Of Polyurethane (PU) With Modified Sand

Soil stabilisation is defined as a technique to improve the engineering characteristics in order to improve the parameters such as shear strength, compressibility, density, hydraulic conductivity. There are many techniques that can be used for different purposes by enhancing some aspects of soil behaviour and improve the strength and properties of soil. One of the cheapest techniques is by using Polyurethane grout, which is workable for construction and enhances the performance of soil compressive strength. Polyurethane (PU) foam is non-toxic, having an indefinite life span and non-environment unfriendly. PU is a chemical substance that normally used in polymer industries for instance resilience foam seating, rigid foam insulation panels and microcellular foam seals. In this research, different percentages of PU content are mixed with sand to test the compressive strength of modified sand. The compressive strength of sand is determined by conducting the Unconfined Compression Test (UCT) with the mold samples of 50mm diameter and 100mm height. The test determines the compressive strength and generates the stress-strain relationship of the modified sand. It is shown that the compressive strength of modified sand will gradually increase with an increasing PU content percentage (varying from 10% (20 kPa) – 95% (500 kPa). Conclusively, this research could be used as the benchmark of ground improvement technique.

Experimental characterization of FRP composite-wood pile structural response by bending tests

A special prefabricated fiber reinforced polymer (FRP) composite shield or jacket was developed to repair wood piles in the field. Two types of load-transfer mechanisms between the wood pile and the FRP composite shield were developed and tested: (1) cement-based structural grout; and (2) steel shear connectors with an expanding polyurethane chemical grout. The objective of this paper is to characterize the structural response of full-size pre-damaged wood piles repaired with the FRP composite shield system. A three-point bending test procedure was used to simulate the response of a pile subjected to lateral loads. The load-deformation response, deflected shape profile, relative longitudinal displacements (slip), strain distribution, ultimate bending moment capacity and mode of failure were evaluated. Wood piles were pre-damaged by reducing approximately 60% of the cross-section over a portion of the pile. It was found that a pre-damaged wood pile repaired using the FRP composite shield with cement-based grout exceeded the bending capacity of a reference wood pile. The repair system using the FRP composite shield with steel shear connectors and polyurethane grout did not fully restore the bending capacity of a reference wood pile; however it can be used for marine borer protection when wood damage is not critical.

A study on applications of polyurethane injection material for ground improvement

The physical and chemical properties of polyurethane-yielding two-component liquid injection mixture and those of the resulting polyurethane solid foam for chemical grouting were investigated. From the chemical experiments on the factors influencing the properties of polyurethane, it was investigated that the behaviors of polyurethane-yielding liquid material and those of the produced polyurethane solid foam were greatly affected by the ground conditions such as temperature, water content and density of soil. The ground reinforcing and water-blocking effects of polyurethane grouting were examined through the field case history of tunnel excavation of the subway under construction.

Assessment of rock mass strength for underground excavations

Chemical grouts are used in a variety of application in civil and mining engineering, including strata sealing, ground stabilization, and support anchoring. Historically, cement-based grouts have performed effectively in cable support post-grouting applications in underground hard rock mines. Polyurethane grouts have been used in coal mines to stabilize poor roof or rib conditions and to mitigate problems associated with water inflows in shafts and tunnels. This paper focuses on the advantages of using an alternative, polyester-based grout instead of traditional grouting systems. A fundamental advantage is the fact that the polyester grout is safer than polyurethane because it does not contain isocyanate, which is recognized as a serious health threat. Laboratory investigations performed at Virginia Tech indicate that mechanical properties of the cured product are consistent with those of other grouts used in grouting applications where reinforcement and strengthening, together with deformability, are desired. Field tests performed in underground coal and limestone mines demonstrate the “pumpability” of the product and highlight several unique capabilities of the system, such as variable gel times and physical properties largely unaffected by water.

Development of a polyester-based pumpable grout

Chemical grouts are used in a variety of application in civil and mining engineering, including strata sealing, ground stabilization, and support anchoring. Historically, cement-based grouts have performed effectively in cable support post-grouting applications in underground hard rock mines. Polyurethane grouts have been used in coal mines to stabilize poor roof or rib conditions and to mitigate problems associated with water inflows in shafts and tunnels. This paper focuses on the advantages of using an alternative, polyester-based grout instead of traditional grouting systems. A fundamental advantage is the fact that the polyester grout is safer than polyurethane because it does not contain isocyanate, which is recognized as a serious health threat. Laboratory investigations performed at Virginia Tech indicate that mechanical properties of the cured product are consistent with those of other grouts used in grouting applications where reinforcement and strengthening, together with deformability, are desired. Field tests performed in underground coal and limestone mines demonstrate the “pumpability” of the product and highlight several unique capabilities of the system, such as variable gel times and physical properties largely unaffected by water.

High strain dynamic modulus and damping of chemically grouted sand

Laboratory resonant column and cyclic triaxial tests are performed to determine the dynamic response (i.e. shear modulus and damping) of chemically grouted sand. The effect of chemical grouting is evaluated as a function of shearing-strain amplitude, confining stress, cycling prestrain, number of cycles, grout type, concentration, and curing time. The test results show that the shearing-strain amplitude, grout type and grout concentration have significant effects on the shear modulus and damping ratio of the test specimens. The increased addition of sodium silicate grout, which produces stiff gels, improved the shear modulus of the test sand. The acrylate (AC-400) and polyurethane (CG5610) grout, which produces flexible (rubber-like) gels, improved the damping capacity of the sand with increasing grout concentration. The addition of chemical grout greatly reduces the effect of cyclic prestraining over untreated sands. In the case of dense sands, the reduction of cyclic prestraining is less pronounced than in loose sands, which have a higher potential for particle movement and reorientation.

Methods to identify and reduce potential surface stream water losses into abandoned underground mines

Methods to identify and subsequently seal surface water loss zones in stream channels were tested by the United States Bureau of Mines at Staub Run, a first-order stream near Frostburg, Maryland, that partially overlies abandoned coal mine workings. Conventional stream gauging was conducted to establish discharge patterns before and after stream sealing. Electromagnetic terrain conductivity surveys were performed within the stream channel to identify zones of increased relative water saturation to depths less than 15 m. Zones of increased conductivity were generally found to be associated with areas exhibiting statistically significant (P ≤ 0.05) gauged flow losses. Conversely, zones that exhibited declining conductivity delineated areas where between-station flows were not significantly different. Using this information on potential loss zones, an experimental grouting procedure was applied by injecting an expandable polyurethane grout to a depth less than one meter into the alluvial streambed over a 180-m section of the stream channel. Before grouting, the study section exhibited a 24 I/sec flow loss; first-phase grouting reduced this to a 14 I/sec flow loss; with a second-phase grouting the losses were only 3 I/sec.

Polyurethane grouts for water stop in tunnels and tunnelling : Cornely, W Proc International Congress on Tunnels and Water, Madrid, 15–18 June 1988V1, P413–418. Publ Rotterdam: A A Balkema, 1988

Polyurethane grouts for water stop in tunnels and tunnelling : Cornely, W Proc International Congress on Tunnels and Water, Madrid, 15–18 June 1988V1, P413–418. Publ Rotterdam: A A Balkema, 1988

At-source control of acid mine drainage

At present, there is no general solution to the problem of acid drainage from mined lands. There are, however, many options to diminish acid discharges, especially where the oxidizing pyrite is located at or near the land surface. These techniques include barrier methods that isolate the pyrite from oxygen or water, chemical additives and inhibition of iron-oxidizing bacteria. This paper emphasizes technology developed during the last decade that includes the addition of high volumes of alkalinity and/or phosphate, the use of surface geophysics to identify problem source areas, the sealing of fractured streambeds using polyurethane grout and the use of anionic surfactants to inhibit the activity of iron-oxidizing bacteria.

Use of polyurethane grouts and grout tubes : Kriekemans, B Int Water Power Dam ContrV36, N12, Dec 1984, P24–26

Most polyurethane grouts used for seepage control are one-component, and water activated. They are prepolymers of a polyisocyanate with a polyol. Some of the polyurethane grouts use an accelerator to regulate their geltime. When they come in contact with water, they react, foam and solidify. There are hydrophobic and hydrophilic water activated polyurethane grouts.

Use of polyurethane grouts and grout tubes : Kriekemans, B Int Water Power Dam ConstrV36, N12, Dec 1984, P24–26

Use of polyurethane grouts and grout tubes : Kriekemans, B Int Water Power Dam ConstrV36, N12, Dec 1984, P24–26