# Improvement of Subsurface Thermal Characteristics for Green Parks
###### Abstract
Prediction models for subsoil temperature suggested in the literature require many parameters to be employed in order to establish a range of expected temperatures. Models based on computational approaches depend on energy balance calculation and heat transport in the soil to solve the heat equation. Other empirical models involve numerous parameters and measurements, which may not be readily available. [PERSON] et al. [7] stated that the thermal conductivity and thermal diffusivity increased significantly for clays compacted on the dry side of the compaction curve at high temperatures. Prediction models can be formulated based on the thermal characteristics of soils and ambient temperature [8]. More advanced, thermo-enhanced viscoplastic models can also be utilized [9; 10]. The thermal characteristics of soil materials, including thermal conductivity, thermal diffusivity, and specific heat capacity, have a significant impact on how much heat is gained and lost from them. Through laboratory trials, [PERSON] et al. 's [11] research looked into the thermal characteristics of clay and sand mixtures. They discovered that when the clay concentration rose, so did the combination of clay and sand's heat conductivity. With more clay present, the specific heat capacity likewise rose, albeit more slowly. These results contribute to our understanding of clay-sand combination heat transfer behavior. In order to examine the heat gain properties of compacted clay-sand mixes at various temperatures, [PERSON] and [PERSON] [12] conducted laboratory studies. Due to clay's higher thermal conductivity and lesser porosity, they discovered that as the clay content increases, the heat gain in the soil mixture increases. Sand particles changed the heat transmission channels, which also changed how much heat was gained. When studying the heat loss characteristics of compacted clay-sand mixtures, it is expected that as the clay content increases, the heat loss rate will decrease due to the reduction in pore size and the increased moisture content within the mixture. When conducting laboratory experiments on compacted clay-sand mixtures subjected to different temperature conditions, the heat gain can increase significantly as the temperature increases from 30 \({}^{\circ}\)C to 50 \({}^{\circ}\)C. Similarly, the clay-sand mixtures at different temperatures will show a decrease in heat loss as the temperature drops from 50 to 30 degrees Celsius. Knowledge of temporal fluctuations in soil temperature is also necessary for vegetation cover or plants. Many plant processes rely on the ambient and surrounding environment [13]. [PERSON] et al. [14] utilized [PERSON]'s law of cooling, which relates the heat transfer coefficient \(\lambda\) to soil temperature Tsoil,t as follows:  
\[\text{Tsoil,t}=\text{Tenv,t}-\Delta\text{T exp }(-\lambda)\]  
Based on the fundamental rules of thermodynamics, several empirical models were developed to forecast soil thermal conductivity measurements [6; 15; 16]. Due to the complexity of the fabric and the nonhomogeneous character of soils, such models need to use a lot of parameters in order to make accurate predictions. In order to arrive at a reliable estimation, predictions were primarily made based on summing up the proportions of composite materials. Moreover, the use of clay-based liners may be complicated by desiccation fissures, which lower thermal conductivity and hydraulic efficiency. Under such circumstances, geosynthetics may be employed to improve mechanical crack resistance [17; 18]. [PERSON] and [PERSON] [19] reported that there were noticeable improvements in the hydraulic performance of liners during various thermal wet-dry cycles, particularly for low-plastic clays. Although high-plasticity clays have a high ability to resist the effects of heat change, the medium-plasticity clays may also provide a comparable benefit [20]. This work is composed of laboratory and field measurements for predicting soil temperature changes at different clay contents when subjected to variable-temperature environments.