# Influence of Alternating Temperature on the Effectiveness of EICP in Consolidating Aeolian Sand
## 1 Introduction  
In recent years, with the development of the economy and the demand for material transportation, the desert highway has gradually become the link of cross-regional economic exchange. However, the natural environment in desert areas is harsh, and sand particles under the effect of wind transport will be deposited near the road surface due to the increase in friction, resulting in sand burial disasters and affecting traffic safety. Microphically induced carbonate precipitation (MICP), a new technology in the field of aeolian sand reinforcement, has received extensive attention from scholars [1; 2]. The basic principle is to use urease from urease-producing bacteria such as _Sporosarcina pasteurii_ to decompose urease and produce carbonate ions. Carbonate ions and calcium ions in the environment use urease bacteria as nucleation sites to produce calcium carbonate crystals, thus filling sand pores and leading to cementation between sand particles [3; 4]. The improved method of using urease to directly decompose urea based on MICP is called enzyme-induced calcite precipitation (EICP) [5]. There are many studies of MICP and EICP in the application of sand defense and solidification. It has previously been observed that calcium carbonate can be cemented on the surface of the sand to form a solid crust layer, which improves the erosion resistance of the sand surface [6; 7]. Similarly, evidence from a number of experimental studies employing wind tunnel tests has established that calcium carbonate is a cementing materialcapable of solidifying sand and exhibits good resistance to weathering [8; 9; 10]. In a desert area, a field experiment of biomineralization crust was conducted, which formed a cured layer of approximately 2-2.5 cm on the aeolian sand surface, indicating that the calcium carbonate cemented layer can also exhibit good strength performance and stability in a desert field environment [11]. However, both the survival and metabolism of microorganisms in MICP as well as the breakdown of urea by urease in EICP are susceptible to temperature variations [12; 13; 14; 15]. When the temperature exceeds 60 \({}^{\circ}\)C, the microorganisms in MICP usually die due to the high temperature and cannot continue to produce calcium carbonate [16]. In terms of EICP, within the temperature range from 15 \({}^{\circ}\)C to 70 \({}^{\circ}\)C, the activity of urease increased with increasing temperature and reached its optimum at 70 \({}^{\circ}\)C, after which further increases in temperature decreased urease activity, and at 100 \({}^{\circ}\)C, urease activity was almost completely inhibited [17; 18; 19]. In desert areas where rainfall is low, the long hours of sunshine and the low thermal conductivity of the sand lead to high surface desert sand temperatures, which can often reach 50 \({}^{\circ}\)C to 60 \({}^{\circ}\)C in summer [20; 21]. The microorganisms in MICP are susceptible to high desert temperatures, which may lead to a reduction in the activity of microorganisms, whereas the urease in EICP is better adapted to temperature variations [22]. Based on solidifying desert sand field tests, [PERSON] et al. found that EICP could be a useful method to improve the resistance of aeolian sand to strong wind erosion [23; 24]. Similar experiments regarding the utilization of EICP to consolidate desert sand can be found in [PERSON] et al. [25]. In addition, the reaction process of the EICP consolidation of sand can last more than three days [26], and the diurnal temperature variation of the desert sand surface can reach more than 20 \({}^{\circ}\)C [27; 21]. Therefore, when EICP is used to consolidate aeolian sand in a desert environment, the influence of diurnal temperature variation must be considered. However, few studies have focused on the influence of alternating temperature on the effectiveness of EICP consolidation, especially in desert areas, where the diurnal temperature variations are significant.