# Characteristics of the Damping Ratio of Undisturbed Offshore Silty Clay in Eastern Guangdong, China
## 1 Introduction  
Guided by the \"Dual Carbon\" goals of peaking emissions by 2030 and achieving carbon neutrality by 2060, China has vigorously developed offshore wind power. By the end of 2023, the total installed capacity had reached 37.6 GW. Looking ahead, China's offshore wind power industry will maintain robust growth. According to the \"2022 Global Offshore Wind Power Conference Initiative\", by the end of the 14 th Five-Year Plan, China's cumulative offshore wind capacity should exceed 100 GW, surpass 200 GW by 2030, and not fall below 1000 GW by 2050. However, in 2021, the Ministry of Finance canceled central government subsidies for offshore wind power. This policy shift aims to promote industry development through market-driven mechanisms and achieve grid parity for offshore wind power. Against this backdrop, there is an urgent need for technological innovation and refined design to optimize offshore wind turbine structures and reduce construction and installation costs. The damping effect from soil-pile interaction plays a positive role in lowering turbine loads and mitigating monopole foundation fatigue, especially under shutdown conditions and misaligned wind-wave scenarios. However, compared to soil-pile stiffness, studies on soil-pile damping in offshore wind turbines remain limited, and no consensus has been reached in the industry. Hysteretic damping in soil-pile interaction refers to the energy dissipated by the soil in the mobilized zone of the pile when subjected to cyclic shear loading. At the microscopic level, the energy dissipation in each soil element is influenced by the soil's intrinsic damping properties and the amplitude of cyclic shear strain. For a given soil type, larger amplitudes of cyclic shear strain lead to higher damping, according to traditional understanding. However, different soils--due to factors such as overconsolidation ratio and plasticity index--demonstrate varying damping behaviors. Within the mobilized zone of the pile, the magnitude of shear strain varies across different regions and distances. Based on extensive finite element parametric analyses, [PERSON] et al. [1] studied the hysteretic foundation damping for a 1 m height horizontal pile slice that was constrained to mobilize a flow-around mechanism, which is thought to represent a _p-y_ segment of a slender pile. Through a comprehensive set of parametric analyses, a scaling relationship between the cyclic horizontal displacement-damping ratio curve of soil-pile interaction at the _p-y_ spring level and the cyclic shear strain-damping ratio curve at the soil element level was established, as illustrated by Figure 1. This soil-pile interaction damping model captures the nonlinear response of soil-pile interaction damping and incorporates the effects of foundation soil properties. Clearly, the damping properties at the soil element level are a prerequisite for studying soil-pile interaction damping. Extensive research on the damping ratio of clay has been conducted by scholars worldwide [2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14], leading to a relatively mature understanding of its damping behavior. A classic study by [PERSON] [15] identified the plasticity index as a critical factor affecting the soil damping ratio and classified all relevant factors into soil physical parameters and static-dynamic loading conditions. Building on this, a damping ratio prediction model was developed using the plasticity index, overconsolidation ratio, effective mean consolidation pressure, number of loading cycles, and vibration frequency as parameters. [PERSON] et al. [16] studied the damping ratios of Quaternary, Tertiary, and older strata, as well as organic soils in the United States, noting significant effects of stratum age and consolidation stress on damping. They proposed a polynomial damping ratio prediction model based on a normalized dynamic shear modulus. [PERSON] et al.