MECHANISED TUNNELLING | TECHNICAL


LOW CARBON BACKFILL GROUT


Sika is launching a new reduced carbon backfill grout for TBMs, called Sika® Stabilizer-7100 TBM.


Mike A. Sposetti, Global Technical Manager (TBM), Underground Construction with Sika Group AG explains the background and provide details


The TBM tunneling industry has lost the technical reasons why backfill grouts are pumped behind the tunnel lining during TBM advance. The primary objective is avoidance of ground


settlements that can be automatically generated by the creation of the annulus void due to the passage of a tunnel boring machine (TBM) in the ground. Secondary objectives, not less important, are the


avoidance of segment floating, the prevention of water ingress into the constructed tunnel, and the mild transfer of longitudinal and radial stresses from ground to the segmental lining. In most of the cases, conventional two-component


(A, B) grouting methods do not fulfill the above basic requirements, thus jeopardizing the quality of the final


tunnel and potentially putting more at risk the life of people using such public infrastructure assets on daily basis. All backfill grouts objectives are strictly linked to


raw material quality, TBM operations and the quality of the final tunnel as a product per se. In this context, the backfill grout durability concept is still, anachronistically speaking, highly dominated by the concrete industry mentality where the Unconfined Compressive Strength (UCS) is measured at 28 days. However, accountability on curing of laboratory samples and detailed procedures of testing and quality control are not yet properly addressed by the industry due to the lack of a proper tailored-made standard to regulate TBM backfill grouts.


Above, figure 1: Example of backfill grout’s quality some time after placement Summer 2024 | 47


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69