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目的 通过无损检测方法评估故宫石质螭首风化和安全程度.方法 首先在现场选取6个螭首进行无损检测,获取各项风化指标(表面风化程度、裂缝大致情况、孔洞、回弹强度、酥粉质量)和安全等级指标(裂缝性质、裂缝数量等具体值,超声波波速、回弹强度).在实验室模拟风化、破损试验,建立超声波波速、回弹强度与抗折强度的曲线关系.最后通过德尔菲法建立评价体系,采用加权平均法获得各螭首的风化等级、安全等级.结果 石材的抗折强度、超声波波速和回弹强度的曲线关系式为fk=0.0004V0.4393R2.9302.确定了6个螭首的风化程度和安全状况水平,其中构件2的表面风化程度最弱、最安全;构件6的安全情况最差,急需采取有效防范措施.结论 该无损检测和健康程度评估研究方法是一种简单、快速、可量化的评价方法,其成果可用于石质文物健康状况的检测和评估工程,以获得其风化等级、安全等级,并作为文物管理决策的依据.

The work aims to study the weathering and safety degree of the dragon heads in Forbidden City by performing a nondestructive testing (NDT). The weathering indices (degree of surface weathering, cracks overview, pores, rebound strength, mass of powder) and safety level indices (crack property, specific values such as crack quantity, ultrasonic velocity, rebound strength) were obtained from non-destructive testing of 6 dragon head samples. Weathering and destructive tests were simulated in the laboratory, curvilinear relationship between bending strength, ultrasonic velocity and rebound strength was established. An evaluation system was built by means of Delphi method, weathering level and safety level of all dragon heads were obtained by means of weighted average method. Weathering level and safety conditions of 6 dragon heads were determined by fk=0.0004V0.4393R2.9302, a curve relation involving bending strength, ultrasound velocity and rebound strength of stone relics. The weathering level of component 2 was the weakest and safest. The safety condition of component 6 was the worst and effective precautionary measures should be taken timely. The nondestructive examination and health status evaluation method provided a simple, rapid and quantifiable method. The test results can be used in test and evaluation project of stony relics, so as to obtain the weathering and safety level of stony relics, and can be regarded as basis for decision-making of cultural relic management.