## 1 Introduction  
Weathered granite, including residual soil and highly and completely weathered rocks, is widespread in South Korea and is used as the support base in the construction of major roads, bridges, and tunnels. It is therefore important to assess the geotechnical properties of weathered granite to ensure satisfactory structural performance and safety. Although geotechnical properties are typically assessed by in situ testing, sampling techniques that minimize the disturbance of the weathered granite sample, such as the triple core barrel method, have been in limited use more recently. However, it is challenging to secure sufficient undisturbed samples that are suitable for laboratory testing due to the frequent occurrence of disturbance during the transportation and fabrication of the test specimens. [PERSON] et al. [1] have recommended that in situ testing should be performed to obtain proper geotechnical properties in the case when it is difficult to retrieve an undisturbed sample. The representative in situ tests applied to weathered granite are the standard penetration test (SPT) and pressuremeter test (PMT). The SPT, which is conducted simultaneously with a borehole investigation, is most widely used in the geotechnical field due to its convenience and economic feasibility. It is used to estimate geotechnical properties such as friction angle, unconfined compressive strength, and elastic modulus based on accumulated data and may also be used to calculate the bearing capacity of the foundation and assess ground liquefaction [2; 3; 4]. However, the equations currently used to determine the geotechnical properties should be used witititcaution because most empirical equations are proposed based on the SPT-\(N\) values measured from soils, and penetration into the highly and completely weathered granite during an SPT is quite subtle. The PMT is used to assess the radial stress-strain behavior of the ground around a borehole and can also be applied for the calculation of the pressuremeter modulus (\(E_{m}\)) and limit pressure (\(P_{L}\)) of the base ground according to the obtained stress-strain curve. The \(E_{m}\) is used to calculate the settlement of a shallow foundation and the coefficient of the horizontal subgrade reaction, as well as the strength parameter of the ground, the bearing capacity of a shallow foundation and a pile foundation using the limit pressure. It is applicable to a wide range of ground types, ranging from soils to weak rocks, and particularly to geo-materials in a transition state between rock and soil, such as weathered granite [5]. However, it is more time-consuming and costly than the SPT and thus its use is limited and it often omitted in small-scale projects. Researchers have used simple regression analyses to investigate the correlation between SPT-\(N\) values and the \(E_{m}\) and \(P_{L}\) interpreted from PMTs to assess the geotechnical properties of grounds with a high degree of reliability, because SPTs are relatively convenient and economical. For example, [PERSON] and [PERSON] [6] proposed nonlinear relationships between \(N\) and \(E_{m}\) and between \(N\) and \(P_{L}\) for weathered granite, including highly weathered granite and residual soil, in Hong Kong. [PERSON] et al. [7] proposed linear relationships between \(N\) and \(E_{m}\) and between \(N\) and \(P_{L}\) based on the results of a test conducted in sandy silty clay developed at a shallow depth (within 2 m) in Denizli, Turkey. [PERSON] and [PERSON] [8] proposed nonlinear relationships between the same parameters for sandy soil and claye soil using the results of tests conducted in Istanbul, Turkey, while [PERSON] and [PERSON] [9] did the same for silty sand and silty clay based on SPTs and PMTs conducted in Mashhad, Iran. However, most of these previous studies dealt with soils with SPT-\(N\) values of \(\leq\)50; none considered weathered granite with an \(N\) value of \(\geq\)50.