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Investigation of the Contribution of Jet Grouting to Soil Improvement and the Effects of the Parameters Used in This Method [ABSTRACT FROM AUTHOR]

Geophysical investigations were conducted using electrical resistivity tomography (ERT) along planned dykes of the HPP Brežice water accumulation basin. The ERT profile is 7.3 km long and is located on the right riverbank of the Sava River on the Krško-Brežice field (E Slovenia). A purpose of the investigations was to determine a boundary between semipermeable Miocene and permeable Plio-Quaternary (Pl-Q) and Quaternary (Q) sediments for the proper design of the jet grouting sealing curtain, which will prevent lateral outflow of water from the accumulation basin. In this paper we present processing of the section between 5100 and 6100 m of the profile line. In this section the measurement template was set to 25 depth levels, because a significant increase in a thickness of the Pl-Q sediments was expected. Modelling of the measured apparent electrical resistivity data was carried out with RES2DINV and RESIX 2DI inversion software. Different inversion parameters were used to create 15 geoelectrical models for each program, which were then compared and evaluated based on borehole data and on previous geological investigations of the area. With the final geoelectrical models it was possible to successfully determine areas of three expected stratigraphic members and limit an electrical resistivity range for each one of them. The boundary is well defined between Q and Pl-Q and also between Q and Miocene sediments with sharp contrast in electrical resistivity between them. A boundary between Pl-Q and Miocene sediments was not that obvious, but it was possible to determine its shape by the use of different inversion parameters. We propose a simplified geological cross section based on the interpreted geoelectrical models and borehole data. Geofizikalne raziskave z metodo električne upornostne tomografije so bile izvedene po 7,3 km dolgemu profilu, ki poteka vzdolž načrtovanih nasipov za HE Brežice na desnem bregu Save na Krško-Brežiškem polju. Namen raziskav je bil določiti mejo med polprepustnimi miocenskimi ter prepustnimi pliokvartarnimi (Pl-Q) in kvartarnimi (Q) sedimenti za načrtovanje t.i. jet grouting tesnilne zavese, ki bo preprečevala lateralni odtok vode iz akumulacijskega bazena. V članku predstavljamo obdelavo odseka med 5100 in 6100 m profila na katerem smo pričakovali začetek pojavljanja večje debeline Pl-Q sedimentov, zato smo meritve izvedli na 25 globinskih nivojih. Modeliranje izmerjenih podatkov navidezne električne upornosti je potekalo s programoma RES2DINV in RESIX 2DI z uporabo različnih parametrov pri izdelavi modelov. Te smo med seboj primerjali in vrednotili na podlagi preteklih geoloških raziskav območja in podatkov vrtin. Z vsakim programom smo izdelali 15 različnih modelov. S končnimi modeli smo lahko uspešno opredelili območja pojavljanja treh pričakovanih stratigrafskih členov in za vsakega podali razpon modeliranih električnih upornosti. Na modelih je dobro viden potek meje med Q in Pl-Q ter med Q in miocenskimi sedimenti z velikim medsebojnim kontrastom v električni upornosti. Nekoliko slabše je definirana meja med Pl-Q in miocenskimi sedimenti, vendar je bilo z uporabo različnih postopkov modeliranja tudi mogoče opredeliti njeno obliko. Na podlagi izdelanih modelov in podatkov vrtin smo za obdelan odsek podali poenostavljen geološki profil, na katerem so predstavljene glavne geoelektrično ugotovljene meje med stratigrafskimi členi. [ABSTRACT FROM AUTHOR]

Utilizando um programa baseado no método dos elementos finitos, analisa-se uma escavação multi-escorada em solo mole, reforçada no fundo com laje de jet grouting. O programa incorpora a teoria multidimensional de consolidação de Biot (formulação acoplada das equações de equilíbrio e de escoamento) com relações constitutivas simuladas pelo modelo de estados críticos p-q-θ. Avalia-se, em particular, da importância da instalação da laje de jet grouting, funcionando como escoramento abaixo da base da escavação, por forma a evitar a rotura do fundo daquela. É dada especial atenção à análise, durante e após o período construtivo, das pressões de água, dos excessos de pressão neutra, das tensões de corte, dos níveis de tensão e dos deslocamentos no maciço, bem como dos esforços axiais nas escoras, dos deslocamentos, momentos flectores e pressões na parede e dos esforços axiais e momentos flectores na laje de jet grouting.

Local scouring is a severe threat to the safety of offshore wind turbines, and it cannot be eliminated completely by traditional protection methods. In this paper, to improve seabed scouring resistance, a new local scouring countermeasure—grouting protection—is proposed, and flume scouring tests are reported. It is found that after grouting, the micro-morphological characteristics of the soil are changed, with the internal friction angle and cohesion of the seabed soil being improved significantly. The grouted seabed has different modes during the development of scouring, i.e., cracking, peeling off, incipient motion, and abrasion. Further analysis shows that the critical shear stress of grouted seabed particles is much greater than that of ungrouted ones, and the ultimate scouring depth of grouted seabed is much lower than that of ungrouted seabed. The protective effect of grouting on local scouring is fully verified: compared with collar protection, grouting protection is more reliable under weak hydrodynamic action, and compared with riprap protection, grouting protection is more efficient under extreme hydrodynamic action. • Proposed a new local scouring countermeasure—i.e., grouting protection. • Found the micro morphology of soil changes before and after seabed grouting. • Revealed the different modes during the development of scouring for grouted seabed. • Verified the protective effect of grouting on local scouring. [ABSTRACT FROM AUTHOR]

Abstract: Many geotechnical projects today have demonstrated a need for improved soil foundation properties, namely physical and mechanical properties. There are currently several soil improvement methods available for this task, including jet grouting (JG) technology. In this method, a slurry grout is injected into the subsoil at high pressure and velocity to destroy the soil structure. The injected slurry (normally cement) and the fragmented soil together create an improved soil mass with better strength, deformability and permeability characteristics. However, due to the inherent geological complexity and high number of parameters involved in this improvement process, the design of its physical and mechanical properties is a very complex task, especially in the initial project stages and in small-scale geotechnical projects, when information is scarce. Consequently, the economics and quality of the improvement can be adversely affected, and it would be beneficial to develop an accurate model to simulate the effects of the different parameters involved in the JG process. In many geotechnical structures, advanced design incorporates the ultimate limit state and the serviceability limit state design criteria, for which the uniaxial compressive strength and deformability properties of the improved soils are needed. A previous study by the author proposed some regression models based on data mining (DM) techniques to predict the uniaxial compressive strength of JG laboratory formulations (JGLF) over time. In the present study, similar tools such as multiple regression, artificial neural networks, support vector machines and functional networks are trained to predict the deformability modulus of JGLF over time. Additionally, the mathematical expressions proposed by the Eurocode 2 and Model Code 1990 that are currently used to estimate concrete stiffness over time are adapted to the JG material. The results show that the novel soft computing model is more accurate and capable of learning the complex relationships between JGLF deformability and its contributing factors. A novel visualisation approach is also applied to the work based on a sensitivity analysis method. Such an approach enables the identification of the most important input parameters and their average influence on deformability predictions for JGLF. Moreover, through the application of DM techniques, a novel approach capable to predict JGLF stiffness based on its unconfined compressive strength and three other variables related to soil and mix properties is proposed. [Copyright &y& Elsevier]

Abstract: Learning from data is a very attractive alternative to “manually” learning. Therefore, in the last decade the use of machine learning has spread rapidly throughout computer science and beyond. This approach, supported on advanced statistics analysis, is usually known as Data Mining (DM) and has been applied successfully in different knowledge domains. In the present study, we show that DM can make a great contribution in solving complex problems in civil engineering, namely in the field of geotechnical engineering. Particularly, the high learning capabilities of Support Vector Machines (SVMs) algorithm, characterized by it flexibility and non-linear capabilities, were applied in the prediction of the Uniaxial Compressive Strength (UCS) of Jet Grouting (JG) samples directly extracted from JG columns, usually known as soilcrete. JG technology is a soft-soil improvement method worldwide applied, extremely versatile and economically attractive when compared with other methods. However, even after many years of experience still lacks of accurate methods for JG columns design. Accordingly, in the present paper a novel approach (based on SVM algorithm) for UCS prediction of soilcrete mixtures is proposed supported on 472 results collected from different geotechnical works. Furthermore, a global sensitivity analysis is applied in order to explain and extract understandable knowledge from the proposed model. Such analysis allows one to identify the key variables in UCS prediction and to measure its effect. Finally, a tentative step toward a development of UCS prediction based on laboratory studies is presented and discussed. [Copyright &y& Elsevier]

This paper presents a generalized approach for predicting the diameter of jet grout columns based on the theoretical framework of turbulent kinematic flow and soil erosion. The proposed calculation method is applicable to all conventional jet-grouting systems and takes into account the full range of operational parameters, fluid properties, soil strength, and particle size distribution, including the effect of the injection time on erosion distance. It was demonstrated that the increase in the jet grout column diameter arising from the use of a compressed air shroud in the double and triple fluid systems is approximately 27-81% for the typical range of air pressure of 0.5-1.5 MPa. The proposed method was applied to four case histories involving four variants of jet-grouting systems, i.e., single fluid, double fluid, triple fluid, and an enhanced triple fluid system. Comparison between the calculated and the measured jet grout column diameters indicated that the proposed method can produce reasonable predictions for a variety of soil conditions. It was shown that jet grout columns formed by the enhanced triple fluid system are larger than those formed by the conventional triple fluid system by approximately 36% on average. The proposed generalized approach allows all the key variables to be considered and is a useful means for the design of ground improvement by jet grouting. [ABSTRACT FROM AUTHOR]

Highlights: [•] Unconfined compressive strength of alkaline activated fly ash grouts increases with density. [•] Fluidity of alkaline activated fly ash grouts decreases with density. [•] Such grouts are more sensitive than cement grouts to curing conditions, being more prone to shrinkage/expansion behaviour. [•] Preliminary results seem to indicate that these grouts have a lower voids volume than cement grouts. [•] Na2O concentration has a significant impact on strength. [ABSTRACT FROM AUTHOR]

The new metro line in Thessaloniki includes, besides the excavation of two twin tunnels, the construction of 13 stations with central platform in settlement-reducing top-to-down construction method. Due to restrictions in available space, it was necessary to dispense with the construction of an inner shell. Further constraints were the soft and highly inhomogeneous soil, the large excavation depths in groundwater, and the earthquake-resistant design of the structures. The special foundation works executed for permanent uplift safety as well for the soil strengthening in front of the excavation walls are described for representative stations. Die neue U-Bahn in Thessaloniki umfasst, neben dem Schildvortrieb zweier Röhren, die Errichtung von 13 Bahnhöfen mit zentralem Bahnsteig in verformungsarmer Deckelbauweise. Wegen der engen Platzverhältnisse musste dabei auf eine Innenschale verzichtet werden. Weitere erschwerende Randbedingungen sind der weiche, stark inhomogene Untergrund, die große Aushubtiefe im Grundwasser und die erdbebengerechte Auslegung der Tragkonstruktion. Für typische Bahnhöfe werden die Spezialtiefbaumaßnahmen zur dauerhaften Auftriebssicherung sowie zur Verstärkung des Fußwiderlagers der tiefen Baugruben vorgestellt. [ABSTRACT FROM AUTHOR]

This paper discusses the seismic retrofit of Tuttle Creek Dam near Manhattan, Kansas, including investigations, seismic analyses, design, construction, and stabilization techniques used. Original plans called for stabilization of the upstream and downstream slopes and installation of an upstream cutoff wall to reduce underseepage. However, constructability and dam safety issues, along with the results of refined seismic deformation analyses, led to cancellation of the jet grouted upstream slope stabilization and cutoff wall. Downstream slope stabilization was to be accomplished by jet grouting or soil mixing, but ultimately was accomplished using a self-hardening cement-bentonite (C-B) slurry to construct transverse shear walls. A total of 351 transverse shear walls were constructed along the downstream toe by primarily clamshell equipment. Typical shear walls are 13.7 m long, 1.2 m wide, and extend 18.9 m deep or about 6.1 m into the coarse foundation sands. The walls are spaced at 4.3 m on center along the downstream toe for a replacement ratio of about 29%. In addition to the transverse shear walls, the relief well collection ditch along the downstream toe was replaced with a buried collector system to further improve downstream stability and underseepage control. [ABSTRACT FROM AUTHOR]

This paper presents a brief overview of artificial intelligence applications in transportation geotechnics, highlighting new approaches and current research directions, including issues related to data mining interpretability and prediction capacities. Several practical applications to earthworks, including the compaction management and quality control aspects of embankments, as well as pavement evaluation, design and management, and the mechanical behaviour of jet grouting material, are presented to illustrate the advantages of using data mining, including artificial neural networks, support vector machines, and evolutionary computation techniques in this domain. This study also propose a novel simplified compaction table for reusing geomaterials and compaction management in embankments and applied one- and two-dimensional advanced sensitivity analyses to better interpret the proposed data-driven models for the prediction of the deformability modulus of jet grouting field samples. These applications show the capabilities of data mining models to address complex problems in transportation geotechnics involving highly nonlinear relationships of data and optimisation needs. [ABSTRACT FROM AUTHOR]

Abstract: When height of retaining walls is small it is rational to install gravity retaining walls. The jet grouting technology often is used installing piles in the sand. Pile diameter can be varied from 0.50 to 1.20 m using single-phase jet grouting with 30÷40MPa pressure. This type of piles applied for the installation of retaining walls too. Low retaining wall constructed using jet grouting pile should be treated as gravity walls. Diameter of the jet grouting piles from which are constructed retaining walls depend on the choice of wall height and from internal friction angle in sand. Influence of interaction between the wall surface and soil on stability is from 10% to 35%. Using of jet grouting technology formed gravity walls allow reduce the volume of mining amount and the installation duration. [Copyright &y& Elsevier]

Abstract: Site remediation involves balancing numerous costs and benefits but often neglects the environmental impacts over the entire project life cycle. Life cycle assessment (LCA) offers a framework for inclusion of global environmental “systems-level” decision metrics in combination with technological and cost analysis. We compare colloidal silica (CS) and cement grouted soil barrier remediation technologies for soils affected by low level radionuclides at a U.S. Superfund site using hybrid LCA methods. CS is a new, high performance grouting material installed using permeation grouting techniques. Cement, a more traditional grouting material, is typically installed using jet grouting techniques. Life cycle impacts were evaluated using the US EPA TRACI 2 model. Results show the highest life cycle environmental impacts for the CS barrier occur during materials production and transportation to the site. In general, the life cycle impacts for the cement barrier were dominated by materials production; however, in the extreme scenario the life cycle impacts were dominated by truck transportation of spoils to a distant, off-site radioactive waste facility. It is only in the extreme scenario tested in which soils are transported by truck (Option 2) that spoils waste transport dominates LCIA results. Life cycle environmental impacts for both grout barriers were most sensitive to resource input requirements for manufacturing volumes and transportation. Uncertainty associated with the efficacy of new technology such as CS over its required design life indicates that barrier replacement could increase its life cycle environmental impact above that of the cement barrier. [Copyright &y& Elsevier]

Abstract: The Twin-Jet method, a newly developed jet grouting technology for the instant solidification of soft ground, is presented. The basic principles of the Twin-Jet method are introduced and sodium silicate (water-glass) is selected as the binder to accelerate the hardening process of an admixture of grout and soil. Two case histories of the Twin-Jet Method, conducted in both a vertical (constructed in sandy soils) and a horizontal (constructed in clay soils) direction, are presented to show their effectiveness. Field construction shows that the admixture of grout and soil can be gelled within 5 to 10seconds. For the case history constructed in sandy soils, coring samples indicate that the jet grout columns are properly formed with a total core recovery of 80–100%, a rock quality designation (RQD) of 81–95% and a column diameter reaching 1.1m, while unconfined compressive strength (UCS) tests suggests that the 28-day UCS is within the range of 5.0–6.0MPa. For the case history constructed in clay soils, field cone penetration tests (CPT) suggest that the column diameter can reach 1.2m, and the UCS test results show that the 14-day UCS can reach 0.5MPa. All of these test results demonstrate the applicability of this newly developed technology in both sandy and clay soils. [Copyright &y& Elsevier]

The use of jet grouting columns to increase the bearing capacity and reduce the settlements of foundations is dealt with, the aim being to formulate a complete design procedure where theoretical analyses and site observations are combined. The study is based on experimental results reported in the literature, which show that jet grouting columns are able to transfer high vertical loads to the surrounding soil but also that structural collapse may locally occur because of a sudden narrowing of their cross sections and/or poor soil cementation. Noticeable attention has been then given to these aspects by interpreting the results of full-scale tests specifically performed to investigate the characteristics of jet grouting columns and their mechanical interaction with the surrounding soil. The results of this analysis form the basis of a numerical method developed to simulate the response of vertically loaded rafts supported by arrays of columns. The nonlinear load-settlement response of axially loaded columns is modeled with the load-transfer curves method customized to account for the irregular shape of jet grouting columns. Extension of the analysis to the whole reinforced foundation is accomplished by considering the mutual interaction between the columns and the upper concrete raft. The variation of column properties is statistically evaluated from the results of field trials, simulated with probabilistic models and introduced into the calculation with a Monte Carlo simulation technique. The main advantages of the proposed method is that the design limit load of the foundation can be expressed in terms of acceptable probability of failure and that the uncertainty arising from the jet grouting process can be experimentally quantified and rationally introduced in the analysis. Benefits and limitations of reinforcement with jet grouting are finally discussed by applying the proposed method to a case study. [ABSTRACT FROM AUTHOR]

Contract B-9528 - Södermalm Tunnel is a good example of urban tunnelling, where tunnel alignments cannot be chosen freely due to existing buildings and subsurface structures. Around ten tunnel crossings and a number of difficult situations underpassing existing buildings were in the scope of Södermalm Tunnel with the main focus on the Maria Magdalena Church. A NATM approach enabled tunnelling of the first double track tunnel in Stockholm's Esker to succeed in very close vicinity of the church. Hauptbaulos B-9528 - Södermalmstunnel ist ein Beispiel für innerstädtische Randbedingungen, wo die Linienführung des Tunnels von existierenden Bauwerken beeinflusst ist und nicht mehr frei wählbar ist. Neben rund zehn Tunnelkreuzungen war eine Reihe von schwierigen Gebäudeunterfahrungen im Auftragsumfang des Projekts B5-9528 - Södermalmstunnel, wobei die Maria-Magdalena-Kirche im Fokus der Bemühungen stand. Ein NÖT-Vortrieb ermöglichte im Nahbereich der Kirche die erste Durchörterung von Stockholms Esker (Oser) mit einem Großquerschnitt. [ABSTRACT FROM AUTHOR]

Deepening foundations is often necessary for renovating old buildings. The process is required for several reasons: first, basement rooms are adapted for activity, since the space of basement rooms is not sufficient, and therefore heightening rooms is essential; second, when the walls of the building are cracked, strengthening foundations is needed; third, renovating buildings increases a load onto foundations. Taking into account the above introduced reasons, an appropriate method for changing the construction of foundations must be chosen. Experience shows that, in most cases, ground resistance under building reconstruction is sufficient and foundations may carry a greater load. Before renovation, the exploitation degree of ground strength must be assessed, which may be expressed as a ratio between foundation pressure and ground resistance. Experience also indicates that, in many cases, the strength of the ground is used irrationally. The foundations of the previously built buildings have a low exploitation degree of strength due to the fact that for designing foundations very simple rules have been used. The other reason is that the ground under foundations takes new characteristics due consolidation over a long period of time. In a compacted soil layer, the angle of shear resistance in sands and cohesion in clays increase. Depending on the maintenance period and soils of base building, ground resistance increases from 1.1 to 1.5 times. Building walls frequently have cracks, as a result of unequal settlements of foundations. In this instance, it is necessary to look for ways to increase the bearing capacity of foundations. Therefore, changing the construction of foundations is required. Foundation basics are often deepened using excavations to adapt the basement rooms for activity and strengthen foundations. The use of this method looks at solving the following questions: excavation depth and width; the distance between simultaneously conducted excavations; the influence of different settlements on building structures; methods for reducing the effects of different settlements. Excavations change the distribution of the pressure under foundations, and therefore excavation depth and width must be calculated considering an increase in pressure under the process of reconstructing foundations. Settlements are inevitable when foundations are deepened. Installing stiffness bands in walls is recommended for reducing the effects from different settlements. Stiffness bands are very effective means of reducing the action of different settlements inevitable when making changes in the con-struction of foundations. Another effective way is the use of jet grouting that accelerates the process of deepening foundation basics. The solid of cemented soil is formed under foundations, and therefore this is a safer and more rapid way than conducting excavations and filling them with concrete. The use of jet grouting reduces uneven settlements. [ABSTRACT FROM AUTHOR]

The Visp bypass is an important link on the Swiss national road A9 from Lausanne to Brig-Glis in the Canton of Valais, which is being improved to provide continuous dual carriageway. About 7 km of the alignment of this 8.8 km long section of the A9 will run through tunnels, with the core structures being the 4.2 km Eyholz Tunnel and the 3.2 km Visp Tunnel. Altogether five underground junction structures have to be constructed for the Visp bypass, of which three will be newly excavated and two are enlargements of the existing Vispertal Tunnel. The following report only deals with the Eyholz Tunnel, which has already been largely excavated. Construction of the main contract of the Visp Tunnel is planned to start in 2012. Die Umfahrung Visp stellt ein wichtiges Teilstück der zukünftig von Lausanne bis Brig-Glis durchgehenden richtungsgetrennten Nationalstraße A9 im Kanton Wallis dar. Die Linienführung des rund 8,8 km langen Teilstücks der A9 verläuft zu rund 7 km in Tunnelbauwerken. Kernstücke sind der 4,2 km lange Tunnel Eyholz und der 3,2 km lange Tunnel Visp. Insgesamt sind für die Umfahrung Visp fünf unterirdische Verzweigungsbauwerke zu erstellen, von denen drei komplett neu auszubrechen sind und zwei aus einer Ausweitung des bestehenden Vispertaltunnels hervorgehen. Die nachfolgenden Erläuterungen beschränken sich auf den Tunnel Eyholz, der bereits zu einem großen Teil ausgebrochen ist. Der Baubeginn des Hauptloses des Tunnels Visp ist für 2012 geplant. [ABSTRACT FROM AUTHOR]

Abstract: Jet grouting (JG) is a soil treatment technique which is the best solution for several soil improvement problems. However, JG lacks design rules and quality controls. As a result, the main JG works are planned from empirical rules that are too conservative. The development of rational models to simulate the effects of the different parameters involved in the JG process is of primary importance in order to satisfy the binomial safety-economy that is required in any engineering project. In this paper, we present a new approach to predict the uniaxial compressive strength (UCS) of JG materials based on data mining techniques. This model was developed and verified using data from a JG laboratory formulation that involves the measurement of UCS. The results of the proposed approach are compared with the EC2 analytical model adapted to the JG material, and the advantages of the new approach are highlighted. We show that the novel data-driven model is able to learn (with high accuracy) the complex relationships between the UCS of JG material and its contributing factors. [Copyright &y& Elsevier]

The article presents a study which investigates the improvement of foundation soil against liquefaction in Romania. The study conducted liquefaction improvement using compaction, permeation, and jet grouting to improve civil engineering foundation soils without inducing vibration that disturb soil mass stability. It determines that the most effective method of underpinning constructions is jet grouting, which offer advantages including in situ workability, strength, and permeability.

In the western part of the Koralmbahn railway line, tests were carried out as part of planned specialised civil engineering works in silty to sandy still water sediments in order to find out about the interaction of jet grouting and dewatering measures with this ground, which is considered to be as geotechnically relatively unfavourable. Small-scale tunnelling work was also carried out to gain experience for the later tunnel construction work in this area. The most important discoveries were: that the jet grouting trials achieved jet grout columns with a diameter of 1.5 m within the still water sediments; and the simulation of a tunnel drive was able to demonstrate that stable conditions at the face can be achieved with the chosen advance support measures. The evaluated results made it possible to optimise the design of the tunnel structures and the forecast performance rates for the grouting works. Im westlichen Bereich der Koralmbahn sind im Rahmen geplanter Spezialtiefbaumaßnahmen in schluffigen bis sandigen Stillwassersedimenten Versuche durchgeführt worden, um Erkenntnisse über die Interaktion von DSV- und Entwässerungsmaßnahmen mit diesem geotechnisch als relativ ungünstig geltenden Gebirge zu erlangen. Zusätzlich wurden durch kleinmaßstäbliche Vortriebsarbeiten Erfahrungen für die späteren Tunnelbauarbeiten in diesem Bereich gewonnen. Als wichtigste Erkenntnisse können genannt werden: Bei den Versuchen zu DSV-Arbeiten waren in den Stillwassersedimenten DSV-Säulen mit einem Durchmesser von 1,5 m zu erreichen; durch die Simulation eines Tunnelvortriebs konnte demonstriert werden, dass mit den gewählten Vorraussicherungsmaßnahmen stabile Verhältnisse im Bereich der Ortsbrust erzielbar sind. Basierend auf den ermittelten Ergebnissen können die bisherige Planung der Tunnelbauwerke sowie die prognostizierten Leistungsansätze bei den DSV-Maßnahmen optimiert werden. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: A great number of damages and injuries affecting buildings are originated either in the foundations or at the supporting ground. This involves a rehabilitation using different techniques of reinforcing and underpinning so as to give the stability back to the architectural collection of buildings. This activity has a great social impact and relevance when dealing with monumental or emblematic constructions where the adopted solution needs to be efficient and safe, and therefore it implies the development of studies before and after the process of rehabilitation to ensure the durability of the intervention. This article shows the research works been done to check the suitability of the adopted solution to consolidate the ground in the restoration of the emblematic building of “La Normal” in Granada. Reinforced jet grouting has been used with the incorporation of fuse elements inserted in the sleeve pipe. It has been defined as a “fuse” since it is a helicoidal tube made of a synthetic material, which can be deformed longitudinally but not transversely and incorporates a spiral steel collar acting as a bellow. With this system, the excessive ground rigidity is avoided as a consequence of the injections which could affect the building if settlements are produced. Seismic techniques have been used, such as the Cross-hole and Down-hole and pressuremetric tests have been carried out to determine the consolidation degree achieved on the supporting soil using reinforced injections. The works carried out serve as a basis to establish actuating and control criteria in soil consolidation treatments using cement–bentonite reinforced jet grouting. [Copyright &y& Elsevier]

Tunnel excavation in cohesionless soils implies the use of a temporary supporting structure prior to lining installation. This temporary structure has to couple safety and economy, and can be conveniently realized using ground improvement techniques (for instance, by creating an arch of partially overlapped subhorizontal jet grouted columns). The adoption of ground improvement techniques results in structures far from having a perfect shape because they are intrinsically affected by defects (in both geometrical and mechanical characteristics), and therefore their design may hide unforeseen risks. As a consequence, this is the typical case in which sophisticated numerical analyses may just give the illusion of being refined, if possible defects are not correctly taken into account. In this paper a simple yet rational analytical method for the design of a nonclosed tunnel supporting structure that may be of some help to this aim is presented. It is done with reference to a simple two-dimensional scheme. In the first part of the paper, a design chart of optimal shape and minimum structural thickness of the cross section of the supporting structure is shown. In the second part, an iterative procedure to verify the stability or to design the minimum structural thickness of an existing supporting structure with a predefined shape is described. This method, coupled with the analysis of structural demand, allows one in principle to plot design charts. This approach can easily take into account structural defects with a semiprobabilistic approach and therefore with a chosen risk level, which is of great help to the designer at least in a preliminary design stage. The proposed semiprobabilistic procedure is applied to the case of a temporary supporting structure realized by partially overlapped subhorizontal jet grouted columns, intrinsically affected by defects in diameter and position. The variability of these geometrical parameters was considered based on the large quantity of experimental evidence collected in field trials by the writers and published elsewhere. [ABSTRACT FROM AUTHOR]

A possible approach is shown for the design of jet grouted umbrellas, which are often used as temporary supports in tunnelling practice. In the current paper it is argued that such an approach should be probabilistic or semi-probabilistic. Based on published experimental data and statistical analyses of diameter and centroid position along the axis of jet grouted columns, a series of Monte Carlo simulations were carried out to find the influence of possible defects within the column in the umbrella static performance, with reference to two extreme subsoil conditions: clay and sand. Geometrical considerations on the minimum overlapping among columns necessary for continuity on the whole span of the umbrella are drawn. It is shown that, owing to defects, the real shape of jet grouted umbrellas is not that of a regular frustum of cone. It is also shown that overlapping decreases along the span. There is a critical length after which structural continuity is difficult to obtain, depending on the statistical characteristics of the jet grouted columns. Defects in axis orientation have a significant effect on this critical length. Static conditions are also analysed, assuming a simplified two-dimensional arch scheme, with reference to the part of the umbrella in which continuity is guaranteed with the assumed level of confidence (95%). The minimum average thickness of the jet grouted umbrella necessary for equilibrium is found, which generally increases as the umbrella opens up along its axis. By combining geometric and static considerations, a simple yet conservative criterion to plan the number of layers of jet columns, their spacing and minimum required diameter-and therefore their initial overlapping-for the design of tunnelling supporting umbrellas is then proposed. [ABSTRACT FROM AUTHOR]

The paper presents a solution executed for the connection of a pre-existing metro tunnel made with a tunnel-boring machine to the structure of a station constructed by the cut-and-cover method. The geotechnical conditions of the site were very difficult: 26 m of man-made fill and alluvial soft silty clay and loose sands, with the water level close to the surface. The tunnel was completely covered by these soft soils. The solution consisted mainly in extending the retaining wall of the station beyond the planes of the portals, in order to confine the tunnel in the stretches adjacent to the station, and creating a volume of treated soil by jet grouting limited by the tunnel lining, the stiff layer underlying the alluvial soft ground, the lateral confining walls and the station wall. The paper presents details of the execution and of the performance of the system. Some conclusions are extracted, emphasising the main advantages of the solution. [ABSTRACT FROM AUTHOR]

This paper deals with the design of jet-grouting cut-offs for dams. Available information from several cases is first reviewed, pointing out the differences between projects concerning dams under construction and operational ones. Various dam types and treatment schemes are considered; functions and requirements of jet-grouting cut-offs are defined; and possible solutions are proposed. Particular attention is devoted to the occurrence of discontinuities along the cut-offs, which may derive from two main factors: deviation of the treatment axes and variation of the jet-column's diameter. A probabilistic design method is developed in order to minimise the risk of such defects. Finally, the drawbacks and advantages of deterministic and probabilistic approaches are discussed. [ABSTRACT FROM AUTHOR]

This paper introduces the superjet-midi (SJM) method, which has been developed to improve the efficiency of jet grouting. The diameters of soilcrete columns constructed with the new method are relatively large (2.4-3.5 m). Advantages and limitations of the SJM method are summarised. To examine the quality of construction, cylindrical SJM specimens were recovered at the site, and field and laboratory tests were conducted. It is found that the jet-sounding technique is a simple and economical measure to estimate the effective diameter of soilcrete columns. The rock quality designation of specimens varies from 79% to 97%, which indicates that the quality of the soilcrete is good. The uniaxial compressive strength qu of jumbo-jet special grout and SJM specimens are similar. The modulus of elasticity Et50 varies from 350 to 1990 MN/m². These data are in good agreement with the range E50 = 100qu -300qu suggested by the JSG Association. Axial failure strains of SJM soilcrete are relatively close to the failure strains for concrete rather than those for soil. [ABSTRACT FROM AUTHOR]

Ome Tunnel is a double-tier highway tunnel with large cross-section of 220–260 m2 excavated at a shallow depth in unconsolidated ground. The tunnel was excavated by NATM. Since the tunnel passes under a road in dense residential area, surface settlement due to tunneling was restricted. Therefore, various auxiliary construction method such as long span steel pipe fore-piling with injection was adopted based on monitoring and analyzing ground behavior during construction. A total of 1060 m of tunneling work was successfully completed without major interruption of work excessive damage on surface residents and other facilities. [Copyright &y& Elsevier]

Jet-grouted columns are commonly used to form cut-off walls in various water-seal project applications. However, affected by geological conditions or other factors, the geometric shapes of jet-grouted columns often deviate from the design values, which affects the water-tightness of cut-off walls. The probability distributions of factors inducing geometric defects in the cut-off walls are analyzed first according to field testing to estimate the water-tightness of jet-grouted cut-off walls with geometric imperfections. Based on this, three-dimensional simulation models of jet-grouted cut-off walls considering geometric defects are established. A simplified theoretical soil seepage model with a cut-off wall is deduced based on Darcy's law. The geometrical parameters in the simulation model are related to the cut-off thickness in the simplified theoretical model according to the equal seepage flow, and a theoretical model of a jet-grouted cut-off wall considering defects is obtained. Finally, the theoretical model is verified by numerical simulation and field observation, and it is found that the theoretical model can get reliable calculation results. This theoretical model can provide a basis for the parametric design of jet-grouted columns and can also predict the degree of seepage flow before soil excavation. [ABSTRACT FROM AUTHOR]