## 1 Introduction  
With the rapid development of the global economy, conventional energy sources such as oil and coal have been consumed in large quantities, resulting in high total carbon emissions [1]. To reduce carbon emissions, many countries encourage the development and utilization of new energy [2; 3; 4]. Geothermal energy, as a kind of clean energy, has wide application prospects in energy supply due to its sustainable and recyclable nature. At present, enhanced geothermal systems (EGS) use hydraulic stimulation to create highly permeable flow paths to retrograde reservoirs and to extract geothermal energy by injecting cold water into injection wells to produce hot water or steam from production wells [5; 6]. However, a series of earthquakes has occurred during geothermal exploration projects in many countries, which has become the primary obstacle to further geothermal energy exploration [7; 8; 9]. For example, in 1997, hundreds of earthquakes with a moment magnitude (\(M_{W}\)) of 1.5 were induced by injection beneath The Geysers, a geothermal field in the United States. A cluster of earthquakes occurred in an EGS project in Basel, which brought the project to a shutdown [10]. The largest earthquake of \(M_{W}\approx 5.5\) during an EGS project occurred in Pohang, Korea, as a result of the acquisition of geothermal energy by hydraulic stimulation, and 50 people were seriously injured [11]. The understanding of the mechanisms of fault reactivation is based on the Mohr-Coulomb criterion, which incorporates the effective stress principle, stating that whether a fault is reactivated or not is determined by the critical shear stress \(\tau_{p}\) and the shear stress \(\tau\). The fault reactivation criteria is as follows [12]:\[\tau\geq\tau_{p}=\mu(\sigma_{n}-p) \tag{1}\]  
where \(\mu\) is the friction coefficient, \(\sigma_{n}\) is the normal stress applied to the fault, and \(p\) is the fluid pressure on the fault. Equation (1) indicates that both an increase in fluid pressure and a decrease in the friction coefficient due to fluid lubrication effects [13] and chemical effects [14] drive the fault into an unstable state [15; 16; 17]. However, [PERSON] [18] suggested that a decrease in pore pressure in a reservoir may also induce fault reactivation and generate earthquakes through theoretical analysis. Field and in-situ tests have controlled the number of earthquakes in EGS to some extent by changing the injection parameters, indicating that fault slip reactivation may be sensitive to the pressure, rate, and volume of fluid injection [19; 20; 21; 22]. Moreover, researchers have noted that earthquakes often occur when the injection stops [23; 24; 25]. Even though a large number of researchers have interpreted these field observations by building two-dimensional geological models, little is known about the influence of fluid injection parameters on fault reactivation [26; 27; 28]. On this basis, laboratory experiments can be further used to study the effects of injection parameters on fault reactivation. So far, most laboratory experiments have focused on direct shear tests or displacement-driven triaxial shear tests [29]. Neither of the above two experiments can reveal the real injection-induced fault slip behavior in EGS. Therefore, some scholars have carried out triaxial injection-driven shear slip experiments to characterize the mechanism of fault slip induced by water injection during geothermal exploitation. [PERSON] [30] changed the fluid injection rate, and the results suggested that it was a higher injection pressure that induced fault reactivation. [PERSON] [31] increased the fluid pressure stepwise on fault samples of different roughness levels, and the results suggested that the fluid pressure for fault slip initiation at high speeds was inconsistent with the theoretical value. In the study of slip modes, [PERSON] [32] injected water into rocks with very different permeabilities and believed that fluid injected in impermeable rocks concentrated on the weak surface, resulting in dynamic slip.