干旱环境下土遗址夯补支顶加固变形机制室内试验研究

Laboratory test of deformation mechanism of rammed roof-propping reinforcement at earthen heritage sites in arid environment

在自然力和人为活动影响下,地处干旱半干旱地区的长城、交河故城、北庭故城等土遗址,其墙体根部因掏蚀而大面积悬空,甚至造成局部区域坍塌。针对夯土遗址根部严重掏蚀问题,采用夯筑支顶加固措施既符合文物保护的基本原则,也遵循保存原材料与原工艺的要求,且加固效果显著。然而大体积夯筑支顶体在固结和失水干缩作用下,与原遗址墙体之间形成较大的裂隙,宽度达1~3 cm。如何控制和减小夯补体与原遗址体之间的收缩缝隙,成为实现大体积夯筑砌补加固的关键。基于固结理论和失水收缩特性,在室内制作不同密度和级配的试块进行固结试验,以及不同形状土样试验的失水收缩量的数据统计,对比分析不同密度、级配条件固结变形、干缩变形的特征,拟合基于传统夯筑工艺的夯补支顶体固结、干缩变形的阈值,初步摸索出了预控大体积垂直方向变形的经验式,为预判大体积夯筑支顶体沉降机制提供可靠的理论依据。

Under the influence of natural forces and human activities, earthen heritage sites in arid and semi-arid regions like Great Wall, Jiaohe Ruinsy, Beiting Ruins were hanged in the air largely by sapping at the base of the wall even causing partial collapse. In this study, rammed heritage sites with serious basal sapping were consolidated by rammed roof-propping, which conformed with basic conservation principles of cultural heritage sites protection and followed the requirement to conserve original material and technology, and also had good reinforcement effect. However, large-sized rammed roof-propping body produced big crack in 1-3 mm width from the original wall under the effect of consolidation and dehydration. Control and reduction of shrinking cracks between roof-propping body and original wall were the key to realize reliability and effectiveness of large-sized ramming repair. Based on the theory of consolidation and dehydration, this study conducted consolidation test with different density and gradation samples indoor, and collected the data of dehydration shrinkage of samples with different shapes. This study made a comparative analysis of the regulation of consolidation deformation and dehydration deformation in the condition of different densities and different clay particle gradations, and analyzed threshold value of consolidation and dehydration deformation for roof-propping body, according to traditional rammed technology and laboratory empirical formula. The empirical formula to control large-sized vertical deformation was preliminarily proposed, which can provide theoretical references for controlling shrinkage settlement of large-sized rammed roof-propping body.