An Innovative Approch for Jet Grouting in Soft Clays

Naresh Gurpersaud, Jim Bruce

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Geotechnical Practice / Risk Assessment and Reliability

ABSTRACT: The expansion of Keswick Water Pollution Control Plant in 2013 included construction of a new effluent outfall into Lake Simcoe. A major section of the outfall sewer was constructed using a microtunnel boring machine. Jet grouting was specified in order to pre-treat the very soft clay below an existing 750 mm sanitary sewer prior to the new outfall sewer tunnel's being constructed beneath it. The jet grouting specification stipulated that no movement of the existing sanitary sewer, resulting from jet grouting operations, was allowed. The double fluid jet grouting process was employed. A pre-production test program was successfully performed to verify jet grouting parameters such as lift rate, rotation rate and injection pressure specific to the soils at this site. During production jet grouting, movement of the sewer was detected, necessitating a temporary stoppage of the work. Without modification to the previously tested jet grouting parameters, an innovative methodology was successfully implemented to eliminate further grouting-induced movement of the sewer. This paper outlines subsurface conditions, results of both the initial and supplemental jet grout test programs, and details pertaining to the innovative methodology employed. RÉSUMÉ L'expansion de Keswick usine d'épuration en 2013 comprenait la construction d'un nouveau point de rejet dans le lac Simcoe . Une section importante de l'égout de l'émissaire a été construit en utilisant une machine de forage de microtunnel . Jet grouting a été spécifié afin de pré-traiter l'argile très molle en dessous d'un égout sanitaire existant de 750 mm avant l'émissaire nouvel égout tunnel de cours de construction en dessous. La spécification de jet grouting stipulait qu'aucun mouvement de l'égout sanitaire existant , résultant d'opérations de jet grouting , a été accueilli. Le fluide procédé d'injection à double jet a été employé . Un programme d'essais de pré-production a été réalisée avec succès pour vérifier les paramètres de jet grouting tels que le taux de levée , le taux de rotation et la pression d'injection spécifique pour les sols de ce site . Au cours de la production jet grouting , le mouvement de l'égout a été détectée , ce qui nécessite un arrêt temporaire de l'ouvrage. Sans modification des paramètres de jet grouting testés précédemment , une méthodologie innovante a été mise en œuvre avec succès pour éliminer la poursuite du mouvement induit par injection - de l'égout . Ce document décrit les conditions du sous-sol , les résultats des deux premiers programmes et complémentaires essai jet coulis et les détails relatifs à la méthodologie innovante employée. 1 INTRODUCTION The community of Keswick, Ontario is located on the east shore of Cook Bay at the southern tip of Lake Simcoe. The Keswick Water Pollution Control Plant was expanded in 2013 to accommodate ongoing significant population growth in the area. Part of the plant expansion included construction, by microtunneling, of a new 1200 mm diameter effluent outfall sewer. Contractor-designed jet grouting of overlapping soil-cement columns was successfully completed to support an existing 750 mm diameter sewer pipe which crosses the new outfall alignment. Jet grouting was required in order to strengthen the ground below the existing sewer to prevent excessive settlement during tunneling at the proposed sewer crossing. The double fluid jet grouting process was used for installation of the soil-cement columns. A test program was undertaken in representative soils in close proximity to the work area. Jet grouting performance was evaluated via exhumation, probing and sampling of the test columns, and no grouting-induced movement concerns were detected. Based on the test program results, production jet grouting commenced using the same parameters employed in constructing the test columns. During production work, movement of the sub-surface monitoring points located along the axis of the sewer was detected and jet grouting was stopped. A comprehensive review of data obtained to that point was conducted and an innovative installation methodology was proposed by the contractor for the installation of the jet grout columns to prevent further movement of the sewer. 2 SUBSURFACE CONDITIONS In the area of the sewer crossing, silty clay and clayey silt materials are present with SPT ‚N' values between 0 and 8, extending from the underside of roadbed down to competent till soil at 13 metres below surface (Fig. 1). The consistency of the native soils vary from a soft to stiff, but are generally soft. In situ vane tests were carried out during geotechnical investigations in 2011, resulting in shear

RÉSUMÉ: novative Approch for Jet Grouting in Soft Clays Naresh Gurpersaud & Jim Bruce

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Cite this article:
Naresh Gurpersaud; Jim Bruce (2014) An Innovative Approch for Jet Grouting in Soft Clays in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper221,author = Naresh Gurpersaud; Jim Bruce,title = An Innovative Approch for Jet Grouting in Soft Clays ,year = 2014}