北石窟寺平顶窟顶板剥落机理及保护技术研究进展

Research on the Physical Mechanisms Causing Deterioration at the Beisikusi Grottoes

北石窟寺是甘肃省陇东地区砂岩石窟的典型代表,受赋存岩性、建筑形制、裂隙发育和环境因素协同作用的影响,北石窟寺洞窟顶板水平层间易拉裂剥离,严重威胁着石窟文物的长久保存。本文基于北石窟寺赋存区域地层岩性、砂岩性能和环境特征的调查研究,详细描述了石窟岩体岩性、原生结构、洞窟形制、水环境、气候及可溶盐等因素对石窟岩体稳定性的影响,系统总结了北石窟寺顶板岩体在卸荷破坏和环境扰动影响下的破坏机理,梳理了石窟寺顶板加固的研究进展,包含砌补、支柱、钢梁吊顶和垂直锚固等技术。基于现场试验研究提出了适合北石窟寺灌浆粘结和柔性锚杆锚固综合治理措施,并以北石窟寺第32窟顶板为加固对象,验证了保护技术的有效性,为砂岩石窟寺顶板剥落病害的科学保护和工程实践提供理论和技术支持。

The Beisikusi Grottoes(Northern Cave-Temple Grottoes)site is representative of the sandstone cave temples in the Longdong region of Gansu Province.Due to the combined effects of lithology,architectural structure,environmental factors and the development of cracking at the site,the cave roofs of the Beisikusi Grottoes are highly prone to cracking and flaking between horizontal layers of stone.Moreover,this process of deterioration is likely to repeat again and again upward through the rock bed in vertical step-like layers that will culminate in a natural arch above the grottoes,seriously threatening the long-term preservation of the caves.Understanding the geological factors and development of the physical mechanisms causing the flaking is therefore crucial to implementing targeted protection measures that will ensure the scientific protection of the cave temples.Based on an on-site investigation of the geological structure,stratigraphic lithology and climatic conditions of the grottoes,this paper reviews various conservation technologies based on their suitability for use at this site,including building masonry,supportive pillars,steel-beam ceilings and vertical anchoring.Results from field research and experiments are then applied to propose a comprehensive set of treatment measures suitable for using grouting and flexible anchoring to bind and reinforce the rock surfaces of the caves.Finally,the proposed conservation plan is applied to the roof of cave 32 in order to test the practical efficacy of the conservation technology,as well as the fitness of the theoretical model to further scientific protection projects endeavoring to prevent flaking in sandstone caves.