关于恐龙化石在发掘过程中因应力释放造成风化破坏的研究

Study on Weathering Damage of Dinosaur Fossils Caused by Stress Release in the Process of Dinosaur Fossil Excavation

在恐龙化石发掘过程中不仅机械扰动会直接导致化石或围岩的破碎,应力释放也会导致化石及围岩表面裂隙的产生及扩张,这些节理裂隙又为水和空气的活动提供了通道,使风化破坏作用更加迅速。作者以分层开挖理论为基础,建立了模拟化石开挖过程的数值模型。通过计算机模拟开挖过程中0m、11m、14m、19m四个深度的等效应力变化过程和XZ方向应力的变化过程发现:开挖前后化石表面的最大等效应力差达到0.34MPa,围岩表面的最大等效应力差达0.3MPa;埋深越大的化石,在开挖露出地面后等效应力的回弹现象越明显,即应力释放越严重;虽然化石表面所受剪应力不大,但其对化石风化的影响比在压应力条件下要大的多,这是导致卸载裂隙产生的主要原因。因此,恐龙化石发掘要逐层缓慢开挖,使化石逐渐达到新的应力平衡,以便减少应力快速释放对化石造成的风化破坏,特别是要做好护坡,最大限度地防止剪应力的产生。

In the process of dinosaur fossil excavation,mechanical disturbance will directly lead to the fragmentation of fossils or surrounding rocks,and stress release will lead to the generation and expansion of surface cracks of fossils and surrounding rocks.These fractures will provide a channel for the movement of water and air,and make weathering damage more rapid.Based on the theory of layered excavation,a numerical model has been established to simulate the process of fossil excavation.Through computer simulation of the process of equivalent stress change and XZ direction stress change at the depths of 0m,11m,14m and 19m,the maximum equivalent stress difference on the suface of fossils before and after excavation is 0.34MPa,and the maximum equivalent stress difference on the surface of surrounding rocks is 0.3MPa.It is found that the more obvious the bullet phenomenon is,the more serious the stress release is.Although the shear stress on the surface of the fossils is small,its influence on the weathering of the fossil is much greater than that under the compressive stress condition,which is the main reason for the unloading cracks.Therefore,the excavation of dinosaur fossils should be slowly excavated layer by layer,so that the fossils gradually reach a new stress balance,so as to reduce the weathering damage caused by stress release to fossils,especially to do a good job of slope protection to prevent the generation of shear stress to the maximum extent.