并在工程稳定分析中也具有重要影响。利用Ansys 数值模拟平台，借鉴花岗岩岩爆试验，分别模拟花

岗岩以0. 025 s /MPa、0. 05 s /MPa、0. 1 s /MPa、20 s /MPa 速率抬升至地表过程中卸荷节理特征。模拟结果表明: 花岗岩卸荷节理的形成主要与围压卸载速率有关，当以0. 025 s /MPa 卸载时，花岗岩成层性明显，在超过0. 025 s /MPa 卸载时，花岗岩出现破裂剧烈、碎裂状和成层性较弱的特点。花岗岩在地下550 m 处出现水平卸荷节理，在700 m 处出现竖直卸荷节理，未出露地表时上覆岩体卸载是卸荷节理出现的主要因素。当接近并出露地表后花岗岩水平卸荷节理受风化、剥蚀作用影响显著，竖直卸荷节理除风化作用还受岩体自重影响。

of the shallow tectonic hierarchy of the crust，and also have an important influence in engineering stability analysis．Using the Ansys numerical modeling platform and referring to the granite burst test，the authors simulate the

characteristics of unloading joints in granitic plutons during the uplifting process to the surface at a rate of 0. 025 s /MPa，0. 05 s /MPa，0. 1 s /MPa，and 20 s /MPa，respectively． The modeling results show that the formation of unloading joints in granitic plutons is mainly related to the unloading rate of confining pressure． When unloading at 0. 025 s /MPa，the granite has an obvious stratification． When unloading more than 0. 025 s /MPa，the granite

cracks violently，showing the characteristics of fragmented shape and weak stratification． The starting point of horizontal unloading joints appears at 550 m underground，while vertical unloading joints appear at 700 m underground．

The unloading of the overlying plutons is the main factor for the appearance of unloading joints of granitic rocks that are exposed underground． When the granites approached and are exposed to the surface，the horizontal unloading joints in granitic plutons are significantly affected by weathering and denudation． In addition to weathering，the vertical unloading joints are also affected by the weight of the granitic plutons．