# Reasonable Support Parameters for Loess Tunnel Under Different Water Contents: A Case Study  
[PERSON] 1  
[PERSON] 1  
[PERSON] 1  
[PERSON] and [PERSON]  
School of Highway, Chang'an University, Middle Section of Nan Erhuan Road, Xi'an 710064, China 1 Correspondence: [EMAIL_ADDRESS] (H.C.); [EMAIL_ADDRESS] (Y.L.) School of Highway, Chang'an University, Middle Section of Nan Erhuan Road, Xi'an 710064, China 1 Correspondence: 202  
to surface buildings caused by unstable support structures in some shallow buried loess tunnels [6; 7; 8; 9; 10], has attracted widespread attention, as shown in Figure 1.  
In order to solve the engineering problems caused by the instability of the support structure during the construction of loess tunnels, [PERSON] relied on a large number of loess tunnel projects to study the mechanical characteristics of the support structure. He used vibrating wire sensors to analyze the deformation and mechanical state of the support structure, and proposed a new type of primary support combination structure with a steel rib, shotcrete, and a locking foot anchor bolt (pipes), which accelerated the construction progress, reduced the construction cost, and ensured the safety and stability of loess tunnels [1; 11; 12; 13; 14]. Some experts and scholars have analyzed the deformation of the rock surrounding loess tunnels through on-site testing and numerical simulation techniques, discovered the deformation laws of the surrounding rock at different construction stages, and pointed out the key processes that affect the deformation of the surrounding rock [15; 16; 17; 18; 19]. These studies provided important construction references for loess tunnels, and their achievements are widely applied in highway and railway loess tunnel engineering. With the deepening understanding of the structural characteristics of loess, engineers have recognized that the stability of loess is intricately linked to its water content [20; 21]. Due to its unique structural morphology and physical-mechanical properties, loess exhibits high sensitivity to water. Research on support structures alone cannot meet the needs of tunnel engineering development. Therefore, extensive research has been conducted on the strength of loess. These studies have determined that soil strength is fundamentally related to its shear strength [22; 23], and variations in water content are the primary factors influencing the deformation and strength characteristics of loess [24; 25; 26; 27]. [PERSON] and [PERSON] found, through their study on the shear strength of loess, that the strength of loess decreases significantly with increasing water content, and the influence of water content on cohesion \(c\) is greater than that of internal friction angle \(\varphi\)[28; 29]. In order to study the relationship between tunnel stability and surrounding rock moisture content, [PERSON] and [PERSON] conducted a large-scale test on collapsible loess at a site with existing tunnels, marking the first such test domestically and internationally, studied the mechanism of the impact of loess collapsibility deformation on tunnel support structures, and revealed the collapsibility process of loess and the variation of stresses in the support structure under long-term immersion [30; 31; 32]. [PERSON] and [PERSON] took the water-rich highway and railway loess tunnels in Ningxia Province as the engineering background, proposed a predictive function model for surrounding rock deformation, compared large deformation control methods through numerical simulation, and conducted in situ control effect tests [33; 34]. The deformation behaviors and stress are  
Figure 1: Engineering problems during the tunnel construction stage. different for loess tunnels under different water content strata. Although the above studies have proposed some measures and provided some help for follow-up study, there is no research on support parameters, especially on reasonable support parameters for loess tunnels with different water content strata, resulting in unnecessary economic waste.