超音波檢測技術應用於傳統建築火成岩火害檢測之評估探討

Applying the Ultrasonic Wave Velocity to Evaluate the Fire Damage of Igneous Rocks Used in Traditional Buildings

臺灣早期的建築，多使用木材、磚、石、土作為建造的原料，在寺廟中更以木材及石材作為支撐建築的主要構件，由於火災發生時木材及石材所受火害毀損的狀況有所差異，木材容易辨識其毀害程度，而石材因為耐火而不易察知其內部損傷情形，因此火災後如何判定石材之損壞程度成為古蹟修復工作之重要課題。本文將探討古蹟寺廟中常見之三種火成岩（花崗岩、觀音石、青斗石）石材，受到加溫至200°C、400°C、600°C、800°C、1000°C、1200°C後冷卻至常溫時，其吸水率、比重以及超音波波速的變化，再對以上試體進行單壓強度試驗，分析溫度與強度的變化狀況，建立使用石材的超音波波速評估石材強度之關係，並作為石材受火害損壞程度評估。接著使用傳統寺廟常用的較大尺寸花崗岩、隴石及青斗石進行實際火害試驗，並探討其超音波速及強度的變化，比較石材在室內高溫試驗與實際火場試驗結果的差異性。結果顯示，實際火場試驗中的花崗岩及隴石雖外層因受熱不均導致大片剝落，但內部石材由超音波檢測以及抗壓強度試驗的結果證實為完好的石材。青斗石因尺寸稍小，受熱不均的影響顯著，造成青斗石分裂成數小塊無法以室內試驗的結果相比較。

Granite, andesite and diabase have been widely used for stone pillars in temples in Taiwan. However, the evaluation of these rocks affected by fire disasters have been limited. This study attempts to develop criteria using ultrasonic technology to evaluate the rocks affected by fire through heated to different temperatures in the oven. The temperatures ranged from room temperature up to the maximum temperature of 1200°C in 200°C steps (200, 400, 600, 800, 1000, 1200), and cooling down to room temperature. Subsequent tests evaluated the variations in: absorption; specific gravity; and wave velocities with temperature. The study also analyses the relationships between compressive strength and heating temperature, and evaluates the relationship between the wave velocity and the compressive strength. In the second part of the study, large-sized granite, Jong-shi stone and diabase, used in traditional temples were tested for simulating the actual fire, to measure the variation between wave velocity and strength. Comparing the differences between the laboratory tests and the actual fire damage tests, the results show that although the outer layer of granite and long-shi stone in the actual fire damaged test caused large pieces of stone to flake off due to uneven heating, ultrasonic technology and compressive strength results confirmed that the internal stone was intact. Due to the small size of the diabase, the influence of uneven heating was significant, and the fracture of the diabase into several small pieces cannot be compared with the results of the laboratory tests.