Application Of Jet Grouting Research Articles

Increasing of strength-rigidity parameters of bases of metallic silos

To date, effective codes of Ukraine limit settlement of foundations of metallic silos to 15 cm. To provide normative settlement of foundation with diameter up to 40 m and more is not always possible without additional essential measures for strengthening or changing base soils. Taking into account high levels of loads, soils of bases in natural condition can not carry stress under the base of foundation and require strengthening. Execution of works on change of soils of bases or installation of soil cushions is not always possible taking into account underflooding of territory, building development that exist near at hand, or other complicating factors. Soil cement after Deep Soil Mixing (DSM) technology, Jet Grouting, injection and micropiles were considered for different types of strengthening taking into account application in great volumes. From analysis of the obtained results, it was determined that soil cement after Deep Soil Mixing technology is the most economically justified method. Application of Jet Grouting is justified during strengthening of soil thicknesses locally separated by depth. Injection and micropiles are used appropriately only in conditions of reconstruction under absence of direct access to the base.

Field study on performance of jet grouting in low water content clay

One drawback to the application of jet grouting for soil improvement is quality control, especially the determination of the diameter and strength of the column, which depends on the technical specifications of the injection and soil type. It has been reported that the initial water content of the clay effects the erosion of cohesive particles. The compressive strength and diameter of a soilcrete column in clay/sand at different jet grouting specifications have been well documented. However, the effect of the initial water content of clay on the performance of the jet grouting method has not been reported. Researchers have not proposed technical specifications for single-fluid jet grouting in remoulded clay with a low water content. The present study carried out 10 full-scale tests to analyse the effect of single-jet grouting specifications on the diameter and uniaxial compressive strength of soil-cement columns in a reclaimed area with low water content clay. The clay-jet grout interaction was evaluated using a microstructural approach and revealed that there is insufficient cohesion between the particles of remoulded clay. The mechanisms of interaction between the particles and the jet grouting is a combination of erosion and penetration of the grout into the soil and into air-filled cracks. In this case, it caused the particles to behave in a manner that is similar to that of silt and sandy soil. The efficiency of jet grouting in this type of soil was better than in clayey soil with a high water content. Thus, the equation previously used to estimate the diameter of the column has been modified by increasing the reference diameter from 50 to 60cm for clayey soil with a low water content. The results show that an increase in the time interval and decrease in lifting step reduced the number of clayey clods in the core and increased the strength of the soil-cement. The maximum strength and diameter were achieved at an energy of 25MJ/m with an optimum injection pressure of 45MPa for single-fluid.

Cyclic lateral response and failure mechanisms of semi-rigid pile in soft clay: centrifuge tests and numerical modelling

Previous studies on laterally loaded piles in clay have mainly focused on flexible and rigid piles. Little attention has been paid to semi-rigid piles (whose pile–soil stiffness lies somewhere between those of rigid and flexible piles), which may behave as either flexible piles or rigid piles, depending on the change in soil stiffness during cycling. This study aims to understand the cyclic lateral response of a repeatedly loaded semi-rigid pile in soft clay and the failure mechanisms of the soil around the pile, through a series of centrifuge model tests and three-dimensional finite element analyses using an advanced hypoplastic clay model. Numerical parametric studies were also performed to investigate the evolution of soil flow mechanisms with increasing pile rigidity. It is revealed that the semi-rigid pile behaved as if it were a flexible pile (i.e., flexural deformation dominated) during the first few cycles, but tended to behave like a rigid pile (i.e., rotational movement prevailed) during subsequent cycles, which progressively softened the surrounding soil. As a result, the mechanisms of soil flow around the semi-rigid pile exhibited an intermediate behaviour combining the mechanisms of both flexible and rigid piles. Three distinctive mechanisms were identified: a wedge-type mechanism near the surface, a full-flow mechanism (within the transverse sections) near the middle of the pile, and a rotational soil flow mechanism (in the vertical symmetrical plane of the pile) near the lower half of the pile. By ignoring the rotational soil flow mechanism, which has a much lower resistance than the full-flow mechanism, the American Petroleum Institute code (published in 2007) underestimated the cyclic bending moment and the lateral pile displacement by 10% and 69%, respectively. Application of jet grouting around the semi-rigid pile at shallow depth significantly altered the soil flow mechanism (i.e., it was a solely wedge-type mechanism around the grouted zone).

Extending chemo-thermal quality assessment for jet grouting

Today quality assessment of jet grouting focuses on the determination of the diameter of the column and the cement content of the improved soil exploiting the exothermal nature of the hydration of cement. This is accomplished by in situ temperature measurement followed by a back-calculation employing a simplified one-dimensional chemo-thermal finite-element simulation model. The underlying assumptions, such as simple geometric properties and disregarding the construction process, lead to the questions of the range of applicability of the existing quality-assessment tool and, in what cases a more refined simulation approach becomes necessary. By means of a two-dimensional simulation, the influence of the geometric properties (height/radius ratio) of jet-grouted columns and of adjacent columns on temperature development is investigated. Finally, the simulation results are compared with the measurements from a construction site, showing the benefit of the proposed model and the simulation approach in the case of complex jet-grouting applications.

A novel approach to prediction of rheological characteristics of jet grout cement mixtures via genetic expression programming

Highly nonlinear flow behavior of cement-based grout mixtures has always become an important issue for experimenters during jet grouting applications. In this viewpoint, an investigation has been addressed in this paper on the applicability of a recent soft computing prediction tool, genetic expression programming (GEP), to the prediction of rheological characteristics (i.e., shear stress, viscosity) of the grout mixtures with various stabilizers (clay, sand, lime) for jet grouting purposes. The experimental data (shear stress versus shear rate with respect to stabilizer dosages) of grout mixtures obtained from rheometer tests have been collected from previous study conducted in a wide range of stabilizer dosage rates (0–100 %, by dry weight of binder). For predicting the shear stress and viscosity as the output variables during the train and testing stages, the input variables in the GEP models included shear rate and stabilizer dosage primarily. As a consequence of GEP modeling compared with measured data, this study reveals satisfactory GEP formulations in a good accuracy (R ≥ 0.86) for predictions of shear stress and viscosity regarding the stabilizer additions. The GEP formulas are also found adequate for modeling the flow behavior of the shear stress–shear rate, alternatively to conventional nonlinear regression and rheological models (Herschel–Bulkley, Robertson–Stiff). For assistance of preliminary evaluations, the derived GEP formulas could be potentially considered in practice for estimations of pumping pressure (shear stress), pumping rate (shear rate) and viscosity of jet grout mixtures.

Technical Note: Example of the Application of Jet Grouting to the Neutralisation of Geotechnical Hazard in Shaft Structures

Abstract The article presents a geotechnical hazard neutralisation technology for shaft structures. The diagnosis of problems with uncontrolled subsidence of the ventilation duct provided by the authors enabled the development of a schedule of works required for the protection and reinforcement of foundation soil in the shaft area. The technology of protection works was selected after the analysis of the technical condition of shaft structures as well as hydrological and geomechanical conditions. Due to the closeness of the shaft lining, it was necessary to form grout columns using jet grouting and low-pressure grouting technologies. The article presents the issues related to the selected technology and its application to the neutralisation of the emergent geotechnical hazard. The method of performance of recommended works was also described together with their impact on the technical condition of structures discussed as well as their functionality and usage.

Prediction of the diameter of jet grouting columns with artificial neural networks

The prediction of the diameter of columns is a fundamental step for the design of jet grouting applications, as harmful consequences may derive from an inadequate selection of the treatment setup. Starting from different perspectives, empirical or theoretical correlations between the mean diameter of columns, the treatment parameters and the mechanical properties of native soils have been provided in the literature. However, the margin of uncertainty with these relations is still relatively large, mostly because of arbitrary assumptions made in their formulation. In order to reduce as much as possible the role of preliminary choices, a method based on artificial neural networks (ANN) is proposed. It consists in training a computer code with a set of experimental observations and in using the established correlations between input and output variables to predict future occurrences. After a brief introduction of the principles and limitations of ANN’s, the paper describes the logical procedure followed for the selection of the variables which better describe the mechanism of columns formation. A database of more than 130 case studies, where jet grouting parameters, properties of soil and diameters are simultaneously reported, has been collected from the literature to train the network. Systematic analyses have been then performed, parametrically varying the structure of the network and the use of data, in order to improve the accuracy of prediction. The comparison with other methods recently published in the literature confirms the good predictive capability of the proposed method. For its practical application, a set of design charts has been produced where the mean diameters of columns are expressed, for all injection systems and soil types, as functions of the soil penetration index NSPT and the specific energy of treatment. Safety factors have been finally computed to take into account the inaccuracy of prediction.

Rheological properties of alkaline activated fly ash used in jet grouting applications

The application of alkaline activated fly ash to soil stabilisation has been recently studied, and although the structural behaviour was adequate, some concerns were raised regarding its apparent viscosity, which proved to be an important issue in jet grouting applications. Therefore, this paper deals with the experimental study of rheology of alkaline activated fly ash-based grouts, namely with: setting time of the freshly mixed grout; fluidity; capillary absorption; shrinkage and expansion behaviour; mass variation during the curing process and density. In order to establish some correlation points with structural performance, uniaxial compression strength (UCS) at 28days curing was also determined. Six different grout compositions, defined based on Na2O (alkali)/ash and activator / ash ratios, were analysed. The activator was composed of sodium silicate and two different sodium hydroxide concentrations: 10.0 and 12.5molal. Results show that the fluidity of the grouts correlate very well with UCS, with an increase of the former resulting in a decrease in the latter, which is a concern in jet grouting applications since this parameter controls the velocity of the grout at the nozzle and the soil/grout mixing capability. In terms of porosity, this type of material seems to be less porous than cement-based grouts. However, drying shrinkage values obtained were in general higher than usual for concrete, which is in accordance with results obtained by other researchers.

Application of jet grouting during foundation reinforcement and reconstruction of historic buildings on land occupied by the state museum and reservation "Tsaritsyno"

Information on the organization and execution of work involving application of jet technology to soil stabilization during reinforcement of the foundations of historical buildings on land occupied by the State Museum and Reservation "Tsitsyno" is presented.

Application of jet grouting on the various contracts in the Lower Inn Valley

AbstractThe jet grouting process is being applied in a number of ways never attempted before as part of the four‐track improvement of the Lower Inn Valley line. In addition to the production of waterproof invert, ground improvement to reduce settlement and for the homogenisation of the excavation cross‐section in mixed face sections, special mined solutions in particular have been made possible by jet grouting. A horizontal jet grout screen for advance tunnel support was produced for the first time under compressed air conditions; the protection of a complete ringshaped jet‐grouted surround also made a mined compressed air drive possible. The jet grouting process was also used to carry out sealing blocks to enable the mined connection of various mechanically tunnelled rescue tunnels to the main tunnel driven by a TBM.The specific conditions on the project combined with the difficult ground conditions typified by Inn gravel sediments, dejection fan deposits and man‐made fill demand all the knowledge and ability of the parties involved. The successful application of the jet grouting technique under these conditions assumes a very high quality of construction and a specifically adapted quality assurance system. Using the example of the contracts H7‐1 Fritzens Tunnel, H4‐3 Stans Tunnel and H8 Jenbach Tunnel, the various applications of the jet grouting technique are described, and also the difficulties that arose during construction.Im Zuge des viergleisigen Ausbaus der Unterinntaltrasse wird das Düsenstrahlverfahren in einer noch nie dagewesenen Vielfalt angewandt. Neben der Herstellung von Dichtsohlen, Bodenverbesserungen zur Setzungsminimierung und zur Homogenisierung der Ausbruchquerschnitte in so genannten Mixed Face Bereichen wurden vor allem bergmännische Sonderbauweisen durch die Anwendung des Düsenstrahlverfahrens erst ermöglicht. Erstmalig wurde ein horizontaler DSV‐Schirm als Tunnelvoraussicherung unter Druckluftbedingungen hergestellt; im Schutz einer ringförmigen vollständigen DSV‐Umschließung konnte ebenso ein bergmännischer Druckluftvortrieb bewerkstelligt werden. Weiter wurden mit dem Düsenstrahlverfahren Dichtkörper ausgeführt, um den bergmännischen Anschluss verschiedener maschinell vorgetriebener Rettungsstollen an die mittels TBM aufgefahrenen Hauptröhren zu ermöglichen.Die projektspezifischen Randbedingungen, verbunden mit den schwierigen Baugrundverhältnissen geprägt von Innschottersedimenten, Schwemmfächerablagerungen und anthropogenen Auffüllungen, verlangen sämtlichen Projektbeteiligten alles an Wissen und Können ab. Die erfolgreiche Anwendung des Düsenstrahlverfahrens unter diesen Umständen setzt eine sehr hohe Ausführungsqualität und ein spezifisch abgestimmtes Qualitätssicherungssystem voraus. Anhand der Fallbeispiele Los H7‐1 Tunnel Fritzens, Los H4‐3 Tunnel Stans und Los H8 Tunnel Jenbach werden die unterschiedlichen Anwendungen des Düsenstrahlverfahrens und auch die im Zuge der Bauausführung aufgetretenen Schwierigkeiten dargestellt.

Jet grouting applications in soft rocks: the Athens Metro case

The Athens Metro is an underground project, which is constructed mainly in soft rock conditions (the Athenian schist formation), and has provided extensive experience for all stages of soft rock tunnelling: the geotechnical investigation, the design and the construction. The present work gives an overview of the geological and geotechnical aspects, which are related to the design of the Athens Metro, and places emphasis on the application of jet grouting techniques for the needs of the project. Features and limitations of the applied jet grouting techniques are examined with the aid of executed full-scale trial tests in two sites of the project, where anticipated extreme surface subsidence and severe over-break incidents needed to be adequately confronted. The results from these tests are appropriately evaluated, and conclusions that can be applied to similar geological and geotechnical conditions are derived. Finally, the efficiency of the applied jet grouting techniques, relative to the acceleration of TBM tunnelling operations and to the minimisation of surface settlements, is addressed, with reference to the detailed work progress records and to the settlement measurements obtained by a comprehensive monitoring programme.

Jet grouting applications in soft rocks: the Athens Metro case

The Athens Metro is an underground project, which is constructed mainly in soft rock conditions (the Athenian schist formation), and has provided extensive experience for all stages of soft rock tunnelling: the geotechnical investigation, the design and the construction. The present work gives an overview of the geological and geotechnical aspects, which are related to the design of the Athens Metro, and places emphasis on the application of jet grouting techniques for the needs of the project. Features and limitations of the applied jet grouting techniques are examined with the aid of executed full-scale trial tests in two sites of the project, where anticipated extreme surface subsidence and severe over-break incidents needed to be adequately confronted. The results from these tests are appropriately evaluated, and conclusions that can be applied to similar geological and geotechnical conditions are derived. Finally, the efficiency of the applied jet grouting techniques, relative to the acceleration of TBM tunnelling operations and to the minimisation of surface settlements, is addressed, with reference to the detailed work progress records and to the settlement measurements obtained by a comprehensive monitoring programme.

Quality control of jet grouting on the Cairo metro

This paper presents a review of the jet grouting works of Line 2 of the Greater Cairo metro system. During the project over 80 000 m3 of ground was treated using the jet grouting method, making this one of the largest jet grouting endeavours worldwide to date. Demanding design requirements for the various jet grouting applications coupled with the difficult Cairo ground conditions provided new challenges to the current jet grouting technology. Inherent difficulties with jet grouting were identified when relying on the method for watertightness at great depths. This paper summarizes the main jet grouting applications used on Line 2 of the Cairo metro and the quality control solutions implemented to overcome difficulties in the work.