Instantaneous nondestructive evaluation of elastic modulus by using knocking ball test on sedimentary and metasedimentary rock slope

The elastic modulus of rock masses is a critical parameter for many engineering applications. However, in situ measurement of the elastic modulus can be challenging and time-consuming. This study established a new in situ method to measure the elastic modulus of rock masses, enhancing prior technology using Hertz's theory. The method involves using a knocking ball, which strikes the rock surface with a spherical steel hammer, providing an instantaneous measurement. The knocking ball method was tested on a variety of rock types, and the results showed a significant correlation (R2 > 0.8) between the elastic modulus of the knocking ball (Ekb) and the in situ uniaxial compressive strength (UCS-Schmidt). The knocking ball method overcomes the limitations of the Schmidt hammer by offering rapid, direct, and multipoint measurements. The knocking ball method is non-destructive, handheld, and easy to use, making it ideal for use in field applications.