Data Interpretation Framework for Pile Thermal Integrity Testing

Abstract

Given the inherent nature of how deep cast in-situ concrete foundations (piles and diaphragm walls) are constructed, evaluating their integrity is difficult. Several well-established methods for testing integrity have been established, but each has its own advantages and disadvantages. In recent years, a new integrity test method called thermal integrity profiling (TIP) has been put into use in deep foundation construction. The primary characteristic utilised in this test is the early-age concrete release of heat during curing; abnormalities such as voids, necking, bulging, and/or soil intrusion inside the concrete body lead to local temperature fluctuations. During concrete curing, temperature sensors installed on the reinforcing cage collect precise temperature data along the entire pile, allowing empirical identification of these temperature variations. This paper proposes a staged data interpretation framework for pile integrity assessment, with the thermal integrity test serving as the initial step. The framework, which is adaptable to different concrete mixtures and pile designs, utilises the heat of hydration and the theory of heat transmission, as well as numerical modelling with the Finite Element (FE) method. It also adopts a staged procedure to assess the as-built quality; for a particular pile, more details are revealed about any anomalies being investigated (including location, size and shape) at each subsequent stage. The primary advantage of this staged process is that it enables practitioners to follow a risk-based approach and decide whether or not to pursue subsequent stages of construction depending on the results they get at the end of each stage. This provides practicing engineers with vital information about the quality of the pile immediately after pile building, so permitting immediate and less expensive repair and remedial work if required.