Statistical Analysis of the Effects of 3D Printing on Concrete-Soil Interface Properties

With the gradual emergence of application scenarios in which construction 3D printing technology is used to build underground structures, the interface characteristics of 3D-printed concrete-soil systems have become a key factor affecting the service performance of underground structures. Aiming to study the difference in interface behavior of 3D printed concrete compared with conventional concrete in ground soil, the interface direct shear tests for different construction surfaces of 3D printed concrete embedded in ground soil were carried out by improving the specimen preparation method to obtain the 3D printed concrete-soil interface shear strength indices. Combining with the data digging in literature analysis, a sample database of concrete-soil interface behavior was established with and without the data obtained in the presented tests, including the shear strength indices of the concrete-soil interface, the physical parameters (coefficient of non-uniformity and dry density) of the soil, and the mechanical parameters (shear strength indices) of the soil. The statistical analysis of the above sample database was carried out by the Bayesian bootstrap method, and the statistical evolution model for the strength indices of the concrete-soil interface was established. The findings obtained are as follows: the dimensionless concrete-soil interface shear strength indices (i. e., the ratio over the shear strength indices of the soil) show a hyperbolic statistical evolution pattern with respect to the coefficient of non-uniformity and the dry density of the soil; the consideration of 3D printing construction imposes negligible influence on the statistical evolution pattern of the dimensionless concrete-soil interface shear strength indices over the coefficient of non-uniformity of soil; the consideration of 3D printing construction leads to the significant narrowing of the ranges of confidence intervals for the dimensionless concrete-soil interface cohesion, and the overall decrease of the upper and lower ranges of confidence intervals and the mean values for the dimensionless concrete-soil interface frictional angle. The findings in this work can provide a scientific reference for the design calculation of 3D printed concrete structures embedded in soil.