The use of non-invasive investigation methods is becoming frequent as a support for the monitoring of water reservoirs and for the management of dam safety. In this context, geophysical techniques are much less invasive than geotechnical tests and allow to obtain two-dimensional or three-dimensional representations of the mechanical parameters of an engineering structure. A case of application of constrained inversion and joint interpretations of non-invasive seismic techniques is discussed, in order to monitor the Dirillo gravity concrete dam, in Sicily. To investigate the foundation soil, a stratigraphic borehole and a vertical seismic profile, carried out in the same hole, were used to constrain the inversion of a MASW. This latter allowed to generate the starting model for a seismic refraction tomography. The results of the seismic surveys on the ground surrounding the dam allowed a detailed seismic characterisation the foundation soil.

Furthermore, for the characterisation of the concrete of the dam, a vertical seismic profile was acquired, using a vertical inspection duct in the dam body, and three seismic refraction tomographies were performed placing sources and receivers on the two opposite walls of the dam. Also in this case the tomographic inversions were constrained by the P wave velocity values obtained from the vertical seismic profile. 2D representations of P wave velocity and the trend with depth of S wave velocity and Poisson ratio allowed an accurate reconstruction of the state of the concrete conservation of the dam. The high velocity values of the P and S waves, together with normal values of the Poisson ratio, suggest that the concrete is still of good quality and local decreases in the P wave velocity are due to moisture and infiltrations.

The results obtained confirm the efficacy of seismic refraction tomography, if appropriately constrained, for the characterisation and validation of concrete in large-scale infrastructures that are difficultly investigable using direct methods.

非侵入性调查方法的使用越来越频繁，以支持对水库的监视和对大坝安全的管理。在这种情况下，地球物理技术的侵入性比岩土工程测试小得多，并且可以获取工程结构机械参数的二维或三维表示。为了监控西西里岛的Dirillo重力混凝土大坝，讨论了一个应用反演和联合解释非侵入性地震技术的案例。为了研究基础土壤，在同一孔中进行的地层钻孔和垂直地震剖面被用来限制MASW的反演。后者允许生成地震折射层析成像的起始模型。

此外，为表征大坝混凝土，使用大坝主体中的垂直检查导管获得了垂直地震剖面，并进行了三个地震折射层析成像，将震源和接收器放置在大坝的两个相对壁上。同样在这种情况下，层析成像反演受到从垂直地震剖面获得的P波速度值的限制。P波速度的2D表示以及S波速度的深度和泊松比的趋势可以精确地重建大坝的混凝土养护状态。P波和S波的高速度值以及正常的泊松比值表明混凝土仍然质量良好，P波速度的局部降低是由于水分和渗透引起的。

所获得的结果证实了地震折射层析成像（如果受到适当限制）对于表征和验证大型基础设施中的混凝土的有效性，而这些基础设施很难使用直接方法进行研究。