脉动水力压裂技术在瓦斯抽采、页岩气开发及地热开发等储层改造领域中展现出起裂压力低、缝网复杂等优势。目前，通过控制流量实现脉动水力载荷输出是工程中的常用方法，但其裂缝扩展机制还不够明确。为此，以砂岩试件为对象，开展了真三轴流量控制式脉动水力压裂试验，分析了泵注频率和泵注速率对泵注压力、声发射能量、裂缝断裂类型及宏观破裂形态特征的影响。结果表明：流量控制式脉动水力压裂的起裂压力、跌落压力及起裂瞬态能量随泵注频率及泵注速率的增加而增大，裂缝扩展面积随泵注频率的增大而减小，随泵注速率的增大而先增大再减小。相较于常规水力压裂，其声发射能量更密集，起裂压力更低，起裂压力最大降低了21.9%，剪切裂纹占比增加5.6%～17.8%，裂缝扩展面积最大增加2.3倍。其脉动水力载荷变化复杂，起裂阶段表现为固定频率、升压力均值和幅值的坡形载荷，裂缝扩展时为固定压力上限、频率和幅值的水平循环形载荷；压力上限、下限和均值与泵注频率及泵注速率呈正相关，压力幅值与泵注频率呈负相关，随泵注频率的增大而先增大再减小。输出的脉动水力载荷类型不同，压裂产生的裂缝扩展特征差异明显。为了提高压裂效果，压裂参数设计要保证输出的脉动水力载荷具有足够的强度和幅值。

Pulsating hydraulic fracturing technology has demonstrated advantages such as lower initiation pressure and complex fracture networks in reservoir stimulation fields including gas extraction, shale gas development, and geothermal exploitation. Currently, the method of controlling flow rate to achieve pulsating hydraulic load output is commonly used in engineering, but the mechanism of fracture propagation remains unclear. To address this, true triaxial flow-controlled pulsating hydraulic fracturing experiments were conducted on sandstone specimens to analyze the effects of pumping frequency and rate on injection pressure, acoustic emission energy, fracture type, and macroscopic fracture morphology. The results indicate that the initiation pressure, breakdown pressure, and transient energy of flow-controlled pulsating hydraulic fracturing increase with the increase of pumping frequency and rate, while the fracture propagation area decreases with increasing pumping frequency and initially increases then decreases with increasing pumping rate. Compared to conventional hydraulic fracturing, the acoustic emission energy is more concentrated, the initiation pressure is lower, with a maximum reduction of 21.9%, the proportion of shear cracks increases by 5.6% to 17.8%, and the fracture propagation area can increase up to 2.3 times. The pulsating hydraulic load varies complexly, showing a ramp-shaped load with fixed frequency, increasing pressure mean and amplitude during the initiation phase, and a horizontal cyclic load with fixed upper pressure limit, frequency, and amplitude during fracture propagation. The upper, lower, and mean pressure limits are positively correlated with pumping frequency and rate, while the pressure amplitude is negatively correlated with pumping frequency and initially increases then decreases with increasing pumping rate. Different types of output pulsating hydraulic loads result in significantly different fracture propagation characteristics. To enhance fracturing effectiveness, the design of fracturing parameters must ensure that the output pulsating hydraulic load has sufficient strength and amplitude.