CASE HISTORY A case study on the application of destructive and non-destructive methods for evaluating jet-grouting column integrity for bridge-pier scour protection (Cuneo, NW Italy) Sabrina Bonetto 1 & Chiara Colombero 1 & Cesare Comina 1 & Nicolò Giordano 1 & Andrea Giuliani 2 & Giuseppe Mandrone 1 & Simone Nicola 3 & Paolo Tible 3 Received: 12 April 2016 /Accepted: 26 December 2017 # Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract A case study on the use of direct and indirect investigations for the effectiveness evaluation of jet-grouting interventions for bridge scour protection is presented. The major concern of this scour countermeasure is that a reliable verification and imaging of the exact dimensions and shape of the grouted elements and their related strength and integrity are difficult to obtain. An integrated cost-effective and slightly invasive approach, by means of indirect surveys, is proposed in this work to limit re- drilling and core sampling of jet columns. Tests are performed on a bridge located in the Province of Cuneo (NW Italy). On site, active fluvial activity was scouring four of the 19 bridge piers and jet-grouting interventions were designed to prevent bridge collapse. A dual approach was consequently applied to evaluate the goodness of jet-grouting treatments: results of direct tests (visual and mechanical characterization of core drillings, with Point Load and Uniaxial Compressive Strength tests) have been compared to indirect investigations (seismic down-hole tests and 2-D cross-hole tomography, laboratory Ultrasonic Pulse Velocity measurements). All the techniques showed potentiality in identifying variations of the jet-grouting properties within the columns. Generally, worsening in jet-grouting properties was coherently identified by a decrease in the seismic velocities and in the mechanical parameters and confirmed by visual inspection of core drillings. Local anomalies and discrepancies between the adopted method were however highlighted and critically discussed as a function of the limitations, disturbances and inves- tigated volumes of each method. Keywords Direct investigation . Geophysical methods . Bridge scour . Jet grouting . Quality assessment Introduction Bridge scour is the predominant cause of bridge failures. It consists of a dynamic phenomenon, related to the erosive action of flowing water and occurs around piers and abut- ments. Scour depends on several factors, such as water depth, flow velocity, pier shape, channel protection measures and sediment type. It can be predicted and taken into consideration in the bridge design phases by accounting for all the key factors causing the phenomenon. This can be performed by adopting empirical equations or by modeling the process with numerical or laboratory approaches (Deng and Cai 2010). However, scour design has only recently become a standard practice. Most of the oldest bridges were not specifically de- signed with proper scour countermeasures. In the field, there is consequently a need for proper monitoring activity on struc- tures potentially affected by scour. In the last two decades, several authors have employed surface geophysical methods to evaluate the progression and dimension of the phenomenon around piers (Parker et al. 1997). Adopted techniques involve radar (Millard et al. 1998; Park et al. 2004), sonar (Hayes and Drummond 1995; De Falco and Mele 2002), combined seis- mic refraction and refraction microtremor (Rucker 2006), * Giuseppe Mandrone giuseppe.mandrone@unito.it 1 Dipartimento di Scienze della Terra, Torino University, Via Valperga Caluso, 35, 10125 Torino, Italy 2 AG3 srl – Spin Off Company of Torino University, Via Valperga Caluso, 35, 10125 Torino, Italy 3 Provincia di Cuneo, Direzione Mobilità ed Infrastutture, Settore Viabilità, Corso Nizza, 21, 12100 Cuneo, Italy Bulletin of Engineering Geology and the Environment https://doi.org/10.1007/s10064-017-1223-0