Grout Flow Research Articles

Groutability of Granular Soils Using Bentonite Grout Based on Filtration Model

This paper describes an experimental and a numerical study on the groutability of granular soils using sodium pyrophosphate (SPP)—modified bentonite grout to investigate its possible application in permeation grouting. While the groutability criteria based on the relative grain size of the soil and the grout have been widely used for particulate grouts, such criteria do not account for the change in groutability of soils due to chemical modifications of the grouts. Moreover, the bentonite grout has different physicochemical properties such as particle size and pH from those in the cement-based grout, resulting in different filtration character, and thus different groutability of soils. Therefore, it is difficult to apply the existing criteria developed for the cement-based grout to the bentonite grout. In this study, the apparent viscosities of various bentonite grouts (5, 7.5, 10, and 12 %, wt/wt %) with 0–4 % SPP were measured using an advanced rheometer. The grouts were injected through sand columns having different effective particle sizes (0.2, 0.28, and 0.31 mm) under two constant pressures (35 and 140 kPa). A 1D filtration model was utilized to simulate the grout flow through the sand columns. A lumped parameter that accounts for physicochemical properties of bentonite grouts was evaluated by calibrating the model with the experimental data. The results showed that the apparent viscosity of 7.5, 10, and 12 % bentonite suspensions decreased approximately 50 % with the SPP concentrations of 1, 3, and 4 %, respectively. Moreover, the lumped parameter increased with the decrease in the effective grain size of the sand and decreased with the decrease in the apparent viscosity of the grout. This implies that filtration during the grout flow was reduced with the SPP modification. The parameter also decreased with the increase in injection pressure and relative density. A new groutability criterion for bentonite grout was proposed based on the relationship between the injected pore volume and the lumped parameter. The criterion was compared to the existing criteria, leading to more accurate prediction of groutability in the tested sands. The proposed groutability criterion will be beneficial to design grouting works by more accurately predicting the groutability of granular soils for SPP modified bentonite grouts than the existing criteria.

수치해석을 이용한 파형 마이크로파일의 지지거동 분석

Recently in Korea, the policy is being proceeded to build a intergenerational housing on artificial ground of railroad site for utilizing rental house. Due to narrow space of rail road site, suitable method have to be developed such as micropiles which is known as a method of a fast construction. However, If micropile is used as foundations for the super structure, construction cost is increases compared with other pile. Consequently, new concept micropile proposed to improve both bearing capacity and cost efficiency of general micropile. New concept micropile consists of waveform cement grout surrounding tread bar that formed by grouting the soil layer with jet grouting method as control the grout pressure and flow. The micropile with waveform is expected to decrease the construction cost by cut down pile length of general micropile. This paper examined the behavior of the new concept micropile with waveform subjected to axial load using two-dimensional axisymmetric numerical analyses method. According to the numerical result, there will cost effectiveness as the pile displacement decreased despite the length of waveform micropile is down about 5% from a general micropile under the same loading condition. Also, the effect of skin friction force which mobilized from the waveform of micropile appeared at relatively soft ground.

Strength Improvement of Loose Sandy Soils Through Cement Grouting

Grouting, which has several applications in the field of civil engineering, was once considered as a mysterious operation. The effectiveness of grouting requires a lot of understanding, skill, meticulous attention and an intuitive perception. Even though grouting was started 200 years ago, it was treated for a long time, as an art which eluded scientific investigation and improvement. Grout is injected under pressure into the material to be grouted until it fills the desired volume of material around the hole or until the maximum specified pressure is attained and a specific minimum grout flow is reached. This paper discusses the strength improvement of loose sandy soils through cement grouting. Various cement percentages (2, 4 and 6 %) were used for grouting medium sand beds in the loosest state. The effectiveness of grouting was evaluated based on the actual cross sectional area of the intact grouted mass at different depths and by determination of cement content at various depths and laterals distances of the grouted medium. The improvement in strength due to grouting was assessed with the help of load tests. 4 % cement grout was found to be more effective in medium sand compared to 2 and 6 %. The results undoubtedly prove the effectiveness of using grouting as an efficient technique in improving the foundation beds of loose sandy soils.

Numerical and analytical analyses of the effects of different joint and grout properties on the rock mass groutability

In this study, an attempt has been made to propose a numerical model to predict grout flow and penetration length into the jointed rock mass using UDEC. The numerical model is adjusted using practical data and presence analytical methods for grouting process. Input data included geomechanical parameters along with grout properties obtained from a case study. The effect of rock mass properties as joint hydraulic aperture, roughness, spacing, trace length, dipping and grout properties as yield value, viscosity and grout pressure was considered on grout flow rate and penetration length. Barton–Bandis joint model has been used to assign joint roughness and strength (JRC and JCS) in the modeling. The results were in a good agreement with analytical and field database. A general function is defined to demonstrate the effects of rock and grout properties on penetration length of grout.

Numerical modeling of the effects of joint hydraulic aperture, orientation and spacing on rock grouting using UDEC: A case study of Bakhtiary Dam of Iran

This study aims at presenting a numerical model for predicting grout flow and penetration length into the jointed rock mass using Universal Distinct Element Code (UDEC). The numerical model is validated using practical data and analytical method for grouting process. Input data for the modeling, including geomechanical parameters along with grout properties, were obtained from a case study. The effect of rock mass properties such as joint hydraulic aperture, spacing, trace length, orientation and grout properties as yield stress and water to cement, w/c ratio was considered on grout flow rate and penetration length. To illustrate the effect of aforementioned properties, models were constructed with dimensions of 40×20m. A vertical borehole with diameter of 60mm and 10m depth was drilled in a jointed rock media. The results were in a good agreement with analytical method. It was observed that by increasing joint hydraulic aperture, grouting flow increases using a power law function. The optimum grout penetration observed with joint sets intersection of 40°-60° as experienced in practice. With an increase in joint spacing grout penetration increases around borehole when spacing exceeds two meters it decreases, gradually.

Gel Characteristics of Urea-Formaldehyde Resin under Shear Flow Conditions

Urea-formaldehyde resin (UFR), one of chemical grouts in which the major ingredients are urea-formaldehyde and resin, is widely used in Chinese coal mines grouting. The gel characteristics of urea-formaldehyde resin (UFR) chemical grout under static conditions have been studied by many researchers. However, there is little research carried out on the gel characteristics under shear flow conditions. In fact, chemical grout like UFR keeps in shear flow conditions before gelling in the grouting process. In order to investigate the gel characteristics of UFR in shear flow conditions, an apparatus which consists of a magnetic stirrer and a viscometer was established. Magnetic stirrer was used to shear UFR at different velocity. Then the changes of UFR viscosity could be recorded by viscometer. As a result, the gel characteristics were summarized under different shear rates, and a formula of gelling is derived. The results show that the grouting flow rate influences the gelling time. Faster flow rates will cause longer gelling time, which means that the time for the grout to gel during the flowing process under shear flow conditions is longer than that under static conditions.

New experience in ground treatment by permeation grouting

In the last few years, ground treatment has made significant progress. Innovative products include environmentally friendly grout mixes based on colloidal silica, which are capable of permeating fine sand even with some silt content. Different mix designs were studied in depth and refined in laboratory trials, in order to define a range of products that could be used for the consolidation and reduction in permeability of soil and fissured rock. In the case of fine and soft soil conditions, low grouting pressure and flow rate need to be utilised, increasing the grouting schedule significantly. In order to carry out the work properly and efficiently, a new injection system was developed, allowing the simultaneous and selective grouting of specific layers. These new mixes and injection system were recently tested in a test programme performed in the very fine and soft soil of Rome, as part of the soil improvements for the construction of the new tunnels and stations for the expansion of the subway system (Roma Metro).

Simulation of repair grout flow in external tendon system

The corrosion of voided tendons has been a long-standing issue in Post-Tensioned (PT) systems because it can lead to the failure of tendons and deteriorate bridge performance. Repair grouting in voided tendons can be one of many rehabilitation options if there are no galvanic couples between the new grouts and original grouts. To identify an appropriate repair grouting method for voided tendons, numerical analysis using a commercial Computational Fluid Dynamics (CFD) program, FLUENT, is utilized in this research. The geometry of voided tendons is a complicating factor when creating reliable models for numerical analysis; thus, a research for the simulation of repair grout flow proposed a simplified model and verified the model with experimental results. Thus, this research performs numerical analyses using the simplified model and assesses various parameters of repair methods and materials. The numerical results indicate that the Pressure-Vacuum Grouting (PVG) method with repair grouts having low viscosity exhibits the best performance for filling voids. If it is determined that filling voids with repair grout is appropriate and prevents future corrosion, it is recommended that voids in the field be filled using the PVG method with grouts exhibiting low viscosities.

Modeling and Validation of Repair Grout Flow in Voided Ducts

External post-tensioned (PT) tendons in bridges are installed inside box girders with high-density polyethylene ducts. Voids in these ducts can lead to corrosion of the PT strands, which could lead to tendon failure. A grout injection is commonly used to protect exposed tendons. Although experiments using external PT tendons have been performed to investigate effective grouting repair methods and materials, these experiments cannot simulate all parameters of grouting repair encountered in the field. In response, the current study uses a commercial computational fluid dynamics program to investigate grout flows in void-containing ducts. A simplified numerical model then is developed based on previous experimental results. This model can consider all parameters of repair grouting methods not covered by experiments. A validation of the proposed model shows close agreement between numerical and experimental results regarding grout flow and repair performance.

Study on Permeation Grouting Using Cement Grout In Sandy Soil

Grouting is the process of ground improvement techniques which is used to improvise the foundation where there is loose state of the soil. Grouting can be classified as permeation grouting, compaction grouting or hydraulic fracturing. Permeation grouting is an effective way to send the grout into the ground without disturbing the soil structure. In this investigation, an attempt is made to study the effect of cement grout in improving the bearing capacity of the sandy soil. Cement grout with different ratio of 10:1 ( Water: Cement) , 9:1, 8:1, 7:1, 6:1, 5:1, 4:1 are injected into the soil. Grouting experiment is performed with perforated PVC pipe in a tank of 20cm x 20cm x 20cm sandy soil. To study the improvement in the strength property of the grouted soil the plate load test is performed with 5cm x 5cm plate on the grouted sand after 3 days curing and 7 days curing. The experimental results revealed that the increase in cement content increases load carrying capacity of the sandy soil. I. Introduction Grouting is the process of ground improvement attained by injection of a fluid like material that is capable of forming a gel and binding the soil particles. Grouting can be permeation grouting, compaction grouting or hydraulic fracturing. Permeation grouting involves the free flow of grout into the soil voids with minimal effect. Grout materials may be solution grouts or suspension grouts. Permeation grouting technique is generally used to reduce ground permeability and control ground water flow, but it can also be used to strengthen and stiffen the ground (CIRIA, 2000). Suat Akbulut et al. (2002) concluded that the soil particle size and the cement maximum particle size have important effects on the successful grouting. Purbi Sen et al. (2011) concluded that, it is desirable to use a mixture of lime and cement or pretreatment of soil with lime before use of cement or use of lime only if possible. Costas.A.Anagnostopoulos, (2005) has concluded that the combination of such material with cement in grouting purpose with respect to water cement ratio contributes significantly to the improvement of grouted soil.

Development and validation of a CFD model predicting the backfill process of a nuclear waste gallery

Nuclear waste material may be stored in underground tunnels for long term storage. The example treated in this article is based on the current Belgian disposal concept for High-Level Waste (HLW), in which the nuclear waste material is packed in concrete shielded packages, called Supercontainers, which are inserted into these tunnels. After placement of the packages in the underground tunnels, the remaining voids between the packages and the tunnel lining is filled-up with a cement-based material called grout in order to encase the stored containers into the underground spacing. This encasement of the stored containers inside the tunnels is known as the backfill process. A good backfill process is necessary to stabilize the waste gallery against ground settlements. A numerical model to simulate the backfill process can help to improve and optimize the process by ensuring a homogeneous filling with no air voids and also optimization of the injection positions to achieve a homogeneous filling. The objective of the present work is to develop such a numerical code that can predict the backfill process well and validate the model against the available experiments and analytical solutions. In the present work the rheology of Grout is modelled as a Bingham fluid which is implemented in OpenFOAM – a finite volume-based open source computational fluid dynamics (CFD) tool box. Volume of fluid method (VOF) is used to track the interface between grout and air. The CFD model is validated and tested in three steps. First, the numerical implementation of the Bingham model is verified against an analytical solution for a channel flow. Second, the capability of the model for the prediction of the flow of grout is tested by means of a comparison of the simulations with experimental results from two standard flowability tests for concrete: the V-funnel flow time and slump flow tests. As a third step, the CFD model is compared with experiments in a transparent Plexiglas experimental test setup performed at Delft University of Technology, to test the model under more practical and realistic conditions. This experimental setup is a 1:12.5 scaled version of the setup of the full-scale mock-up test for backfilling of a waste gallery with emplaced canisters used in the European 6th framework project ESDRED ( Bock et al., 2008). Furthermore, the plexiglas setup is used to study the influence of different backfill parameters. The CFD results for a channel flow shows good comparison against the analytical solution, demonstrating the correct implementation of the Bingham model in OpenFOAM. Also, the CFD results for the flowability tests show very good comparison with the experimental results, thereby ensuring a good prediction of the flow of grout. The simulations of the backfill process show good qualitative comparison with the plexiglas experiment. However, occurrence of segregation and also varying rheological properties of the grout in the plexiglas experiment results in significant differences between the simulation and the experiment.

Experimental Research on Rheological Properties of Cemented Mortar in Tail Void Grouting of Shield Tunnel

Grout flow pattern and rheological parameters determine grouting pressure transfer process in annular tail void and filling rate for shield tail void. However, cemented mortar is a mixture of cement, fly ash, sand, bentonite and water, which lead to grout rheological properties and rheological parameters are difficultly determined. Based on orthogonal experimental design method, grout rheological properties were tested by rotational viscometer. Utilizing variance and poly-nonlinear regression analysis, the qualitative and quantitative relationships between mix ratios and rheological parameters were obtained respectively. It is shown that cemented mortar flow pattern commonly agree with Bingham fluid type, and plastic viscosity varies between 1 and 4Pa•s, and shear yield stress varies between 10 to 40Pa respectively. Water-binder ratio and bentonite-water ratio are key influencing factors for grout rheological parameters. With the water-binder ratio increasing and bentonite-water ratio decreasing, plastic viscosity and shear yield stress present reducing tendency.

Grout and bentonite flow around a TBM: Computational modeling and simulation-based assessment of influence on surface settlements

Adequate consideration of the various interactions between the Tunnel Boring Machine (TBM) and the surrounding underground is a pre-requisite for reliable prognoses in shield supported tunneling based upon numerical analysis. In addition to face support and the grouting of the annular gap the contact conditions along the shield skin between the moving TBM and the surrounding, deforming soil constitute the most relevant component of TBM–soil interactions in mechanized tunneling. This paper is concerned with the analysis of the interface conditions between the shield skin and the soil and its adequate numerical representation in the context of a process-oriented numerical simulation model for mechanized tunneling. The situation around the shield skin is influenced by the design of the Tunnel Boring Machine, the deformational behavior of the surrounding underground and by a possible inflow of process liquids into the steering gap. A novel simulation method is proposed which allows to model the viscous flow of the process liquids into the steering gap and its interactions with the face support, the tail void grouting, the deforming soil and the moving TBM. The proposed numerical model for the TBM–soil interaction is part of a recently developed three-dimensional, process-oriented finite element model for shield tunneling ( Nagel et al., 2010). It allows to investigate the effects of the inflow of process liquids into the steering gap during TBM advance considering realistic machine-related and geological conditions. It is, in particular, capable to compute the pressure distribution within the developing liquid film in association with the face support and grouting conditions and to predict its influence on the surface settlements and the overall TBM–soil interaction affecting, e.g. the hydraulic jack forces or shield deformations.

PC 그라우트의 재료분리 및 PC 빔 그라우팅 충전성에 관한 연구

이 논문에서는 포스트텐션 구조물에 적용되는 그라우팅 품질확보를 위한 재료개선 및 실험과정을 기술하였다. 그라우팅이란 강연선이 삽입된 덕트를 시멘트물질로 채우는 공정이다. 국내에서는 아직 그라우팅의 품질과 포스트텐션 구조물의 내구성에 대한 관계가 인식되지 않아 적절한 품질관리에 어려움이 있다. 국내표준시험법은 강연선에 의한 심지효과(wick effect)를 고려하지 않기 때문에 시공 시 발생할 수 있는 재료분리량을 평가하기 어렵다. 따라서 현 품질기준을 만족하는 그라우트를 사용하더라도, 시공 시 과다한 불리딩 수나 재료수축이 발생할 수 있다. 이 연구에서는 그라우트에 관련된 해외기준과 표준시험법을 조사하여 국내기준 및 표준시험법과 비교한 후 해외기준에 준하는 성능을 나타낼 수 있는 그라우트 구성성분비 및 혼화제를 제시하여 보았다. 개선된 그라우트의 성능을 해외표준시험법에 따라 일반적으로 적용되고 있는 그라우트재와 비교하였으며 PC빔의 덕트형상을 고려한 목업시험을 통하여 흐름유형(flow pattern) 및 충전성능을 관찰하였다. 이 실험을 통하여 그라우팅의 성능은 재료특성에 의하여 높은 영향을 받으며 적용대상의 기하학적 형상에 따라 상이한 충전특성을 가진다는 것 알 수 있었다.

RC기둥의 내진성능평가를 위한 재료비선형 상사법칙

지진에 의한 사회기반 구조물의 손상은 대형참사를 유발할 가능성이 크므로, 적절한 내진성능평가가 이루어져야한다. 특히 지진하중 하에서 구조물의 거동은 상부 하중을 지탱하는 기둥의 거동에 지배되므로 기둥에 대한 해석 및 실험을 통한 내진성능평가는 가장 핵심적인 요소이다. 현재 내진성능평가 실험의 일환으로 준정적실험, 유사동적실험, 진동대실험 등이 대표적으로 수행되고 있으며 이러한 실험을 수행 시 시험체의 크기, 실험장비 성능의 한계, 경제적인 이유 등으로 원형 구조물을 대신하여 축소모형을 통해 실험을 수행하고 있다. 이러한 축소모형실험을 위해서는 적절한 상사법칙을 적용해야 하는데, 현재 일반적으로 적용되고 있는 상사법칙은 탄성범위 내에서 유도가 되어 있기 때문에 지진하중하 구조물의 비탄성 거동을 예측하는데 무리가 있다. 또한 마이크로콘크리트를 사용한 축소모형에 대해서는 필연적으로 재료특성에 있어서 원형재료와 축소모형재료 사이에 왜곡이 발생하여 결과의 신뢰성에 영향을 주게 된다. 따라서 이 연구에서는 재료의 왜곡과 비탄성 거동을 고려하여 새로운 상사법칙을 제시하였다.

Field study of the influence of various jet grouting parameters on soilcrete unconfined compressive strength and its diameter

0. Natures and scopesSoilcrete mass is the result of jet grouting operation, which hasspecial characteristics such as high strength, low deformability andvery low permeability. Specifications of soilcrete columns that areachieved from the jet grouting procedures from the diameter andstrength aspect depend on jet grouting parameters such as groutpressure, lifting speed, number and diameter of nozzles and c/wratio and specifications of local soil. Due to the extensive range ofeffective parameters and dependency of conclusion to local soil, it isdecided to set some trial tests in constant local soil to achieve theoptimized jet grout parameters and c/w ratio. Therefore, this paperpresents new relations between soilcrete uniaxial compressionstrength and its diameter with lifting and rotating speed, c/w ratioand grout pressure. For this purpose, air pressure, air flow, waterpressure, water flow, number and diameter of nozzles and local soilspecifications are held constant, and then the grout pressure values,c/w ratio, lifting speed and rotating speed are changed, respectively,and UCS and diameter of the columns are recorded. According tothe numerical results obtained from experiments: (1) with increasein the grout pressure, UCS (MPa) of soil and diameter of soilcreteincreases logarithmically; (2) with increase in the c/w ratio, UCS(MPa) of soil and the diameter of soilcreteincreases logarithmically;(3) with increase in lifting and rotation speed, UCS (MPa) of soil anddiameter of soilcrete decrease logarithmically.1. IntroductionJet grouting is a very attractive method for various applicationsand has been effective in many instances. One of the mostimportant advantages of jet grouting is that different types of soilscan be used in such a method. Also, the strength and permeabilitycan be improved by means of this technique. This method is asuitable substitution for common injection methods, chemicalinjection, trenching (plastic concrete and grab), piling system,foundation and/or using compressed air with the freezing methodin tunnel building. In this method, the mixture of groutingpenetrates in pore spaces, joints, cracks and voids of rock and soilstructures and optimizes the physical and mechanical character-istics of these structures, thus the penetrateability and deform-ability of layers will become low and on the other hand thestrength of these layers will be increased [1]. The jet groutingmethod is frequently used as a mean for ground improvement,especially in shield tunneling, and also in all sorts of foundationtreatment in recent years [2,3].Generally, the most important parameters that affect jetgrouting designing are soil type, mixture influx between soiland grout, exiting jet energy from nozzle, grout flow rate, rotatingspeed and lifting speed [4]. The parameters that should beassigned in the single fluid system are: grout pressure, numberand dimensions of nozzles, cement/water ratio, rotating speedand lifting speed. In the double fluid system, in addition toparameters that have been mentioned in single fluid system, airpressure and its flow rate should be assigned as well. But in thetriple fluid system, the number and dimension of water and airnozzles should be assigned in addition to the seven parametersthat have been previously mentioned [5].In discussion of the effects of soil material properties on the jetgrouting process, many researchers have described the soil’sbehavior, using the various parameters. Nikbakhtan and Osanloo[1] have shown that by increasing the grout pressure and flow, theUCS (MPa) of soil increases logarithmically. Xanthakos et al. [5]and Covil et al. [4] showed that in soft grounds and also groundswith high cohesion, effective diameter of soilcrete will decreasewith increasing the standard penetration test ‘N’ values. Yoshitakeet al. [3] suggested a nozzle with 4mm diameter to prevent it ofbeing obstructed. Covil et al. [4] and Xanthakos et al. [5] has

Experience with the real time grouting control method

AbstractA new concept of “real time grouting control method” is described by which grout penetration and grouting control are made applicable in real time by applying theories for grout spread. The stop criterion with this method can be related to achieved grout spread, and grouting may be considered complete when the grout penetration for the smallest fracture to be sealed is above a predetermined target value, or before the grout penetration for the largest fracture aperture reaches a certain maximum limiting value. It might also be possible by online monitoring of the process to predict the course of the grout spread and flow and to analyse the risk of uplift and jacking. Four tunnel projects in Sweden are presented in the paper. These references indicate that the real time grouting control method may be applicable to real grouting design and control.Nachfolgend wird ein neues Konzept einer “Echtzeit Kontrollmethode für Injektionen” beschrieben, das für das Eindringen von Injektionsgut im Fels und für die Prozesskontrolle neuartige theoretische Überlegungen zur Ausbreitung des Injektionsguts im Untergrund ansetzt. Das Abbruchkriterium kann mit dieser Methode auf die erreichte Ausbreitung bezogen werden. Die Injektion kann danach dann als abgeschlossen angesehen werden, wenn die Verfüllung der kleinsten zu behandelnden Kluft ein vorgegebenes Maß überschritten hat oder bevor die Verfüllung der größten zu behandelnden Kluft einen vorgegebenen Maximalwert erreicht. Mit dieser Methode kann bis zu einem gewissen Grad auch der Verlauf, die Rate und die Ausbreitung von Injektionsgut vorhergesagt werden. Weiterhin kann analysiert werden, wann das Risiko von örtlichen oder generellen Hebungen eintritt. Vier Schwedische Tunnelprojekte dienen in diesem Beitrag als Beispiele der Anwendung dieser Kontrollmethode. Diese Referenzen sollen auch zeigen, dass die Methode praxistauglich ist.

The PenetraCone, a new robust field measurement device for determining the penetrability of cementitious grouts

One of the most crucial parameters for successful grouting is to ensure that the grout can penetrate the necessary apertures. For the most commonly used grout, cementitious grout, the available methods for determining the ability to penetrate apertures involves several measurements with different meshes or similar, which need to be evaluated. However, during the grouting process in the field there is rarely any time for evaluation and the most commonly used field method today stipulates a mesh width through which a certain volume need to pass. This implies that only an indirect measurement of the penetrability is performed. In order to perform direct and fast field measurements of the penetrability, a new, robust measuring device has been developed at Chalmers University of Technology in Gothenburg, Sweden. The device is named PenetraCone and the measuring part consists of a gap that is formed between two conical cylinders. The penetrability characteristics are measured by decreasing this gap as grout flows through. The gap is measured using a dial indicator gauge. Initial tests with the PenetraCone show that two characteristic gaps or widths can be evaluated. The width as the grout flow goes from continuous flow to dripping is termed b filter and when the flow stops completely it is termed b stop . The parameter b filter is related to the commencement of clogging or filtration of the cementitious grout. This means that for apertures larger than b filter the cement passes unrestricted but for narrower apertures filtration will commence. This filtration process will occur in apertures down to b stop , which indicates the smallest aperture that the cement can pass through and for apertures below b stop the cement will not penetrate at all. The device is easy to use and the tests show that consistent values are obtained. The accuracy seems good enough for use as a control of the penetrability of cementitious grouts in the field. For use in production, the PenetraCone should be placed on the grouting rig, after the mixer, so that direct measurements can be performed on the grout that will actually be used for grouting. By relating the measured parameters to the penetrability requirements, quick decisions regarding the quality of the grout can be made directly on the grouting rig.

The influence of grout and bentonite slurry on the process of TBM tunnelling

AbstractThe bentonite and grout flow around a TBM is elaborated, as well as grout flow along the lining. The calculated grout flow along the lining is compared with the results of measurements. Measurement data for the flow around the TBM are not available. Both the bentonite and the grout are modelled as a Bingham liquid and it will be shown that, due to the relatively low flow velocities, the yield stress is the governing parameter. The results of the calculations show that both the flow around the TBM and the flow around the lining may significantly influence loading on the TBM, the soil, and the lining. The bentonite and grout flow around the TBM may result in a lower volume loss than calculated when assuming that the soil follows the tapered TBM. The grout flow and especially grout consolidation lead to lower pressures around the lining if the tunnel is constructed in sandy soil.

Effect of grout pressure and grout flow on soil physical and mechanical properties in jet grouting operations

Jet grouting is a method for improving soil characteristics. In this method, grouting of cement slurry with high pressure and velocity causes damage to soil structure. Excavated grains of soil are then removed from the borehole and are replaced with cement slurry. The grains that remain around the borehole mix with cement slurry and produce an improved soil mass of soil. This mass is called “soilcrete”. Soilcrete has special characteristics such as high strength, low deformability and very low permeability. The jet grouting process and its results are affected by various parameters of the soil material and jet grouting system. This paper discusses the effects of jet grouting process on the soil properties before and after the operations, and the effects of grout pressure and grout flow on soilcrete's uniaxial compression strength (UCS). For these purposes, five types of the laboratory tests have been done on the jet grouted soil: uniaxial compression, triaxial compression, direct shear, Brazilian indirect tension, and Schmidt hammer tests. According to the numerical results obtained from experiments, by increasing the grout pressure and flow, the UCS (MPa) of soil increases logarithmically. In addition, jet grouting dramatically increases properties such as cohesion and friction angle.