Natural‐gradient tracer experiments in epikarst: a test study in the Acqua dei Faggi experimental site,southern Italy

Two natural‐gradient tracer experiments were carried out using borehole fluorometers in order to characterize the internal structure of epikarstic horizons and analyze subsurface flow within these high‐conductivity layers. The experiments were carried out in a test site in southern Italy where the epikarst is made up of an upper part with pervasive karstification and a lower part without pervasive karstification. Injection and observation boreholes were 6.9 m apart. An initial experiment demonstrated that wider (conduits) and narrower (fractures and bedding planes) openings coexist in a well‐connected network within the lower epikarst. The adjusted aperture of the opening network (105 μm) suggests that conduits are subordinately developed. The lower epikarstic horizon is hydraulically similar to granular porous media and Darcy’s law can be applied to describe groundwater flow. A small value of longitudinal dispersivity (0.13 m) shows that variations in the velocity field in the direction of flow are less significant than those typical of carbonate systems at the same experiment scale. A second experiment demonstrated that longitudinal dispersivity (2.42 m) in the upper epikarst is in agreement with findings in other carbonates at the same experiment scale. However, despite the higher dispersivity and more pervasive karstification, the mean tracer velocity (3.7 m day^?1) in the upper epikarst is slightly lower than the velocity in the lower epikarst (13.6 m day^?1).     

秦俑二号坑出土一件彩绘跪射俑的保护修复

本研究针对秦俑二号坑出土的一件彩绘跪射俑进行了保护修复,是在考古出土现场保存状况、文物病害及病害机理科学分析的基础上进行的现场保护与实验室保护修复。现场保护重在稳定文物状态和应急处理;实验室保护则依据文物保护程序进行保护修复,在进行文物表面清理工作后,使用AC33(丙烯酸乳液)及PEG200(聚乙二醇)加固彩绘层,使用环氧树脂对陶俑进行了粘接修复,收到了良好的效果。此彩绘陶俑的保护修复工作可为以后大型彩绘文物的保护修复提供参考和借鉴。     

Experimental Investigation on the Seismic Behavior of the Semi-Rigid One-Way Straight Mortise-Tenon Joint of a Historical Timber Building

ABSTRACT

This article aims to disclose that the deformation and damages of the one-way straight mortise-tenon (OWSMT) joint, the key force transmission connection of traditional wood buildings, lead to a significant reduction in structural safety of ancient timber structure. For this purpose, the damage of mortise joint in practical engineering wassimulated by controlling the gap and width between mortise and tenon. A total of 23 groups of scaled 1:2 OWSMT joint specimens were fabricated and tested subjected to cyclic loadings, and the hysteretic curves of OWSMT joint with different damage degrees were obtained. Through skeleton curves, stiffness degradation curves, and equivalent viscous damping curves of the OWSMT joint, the seismic performance of damaged wood joints was quantitatively analyzed. The results show that, with the increase in the gap between the tenon and the mortise, the slip between them became increasingly obvious, the fullness and peak of the hysteresis curve gradually decreased, the gradient of the skeleton curve also dropped, and both the stiffness degradation curve and the equivalent viscous damping curve are gradually reduced. The research findings shed new light on the seismic assessment of aging timber buildings.     

Structural Assessment of Ancient Masonries before and during a Rehabilitation Process

ABSTRACT

The rehabilitation of old buildings requires detailed knowledge of the mechanical characteristics and stress state of the structural elements, which play an important role in the intervention process. In this sense, non-slightly destructive tests can estimate structural characteristics with good precision at relatively low costs. Consequently, this article presents a device, based on the flat jack technique, applied to continuous stress monitoring over time. It also focuses on the onsite determination of service stresses and its continuous monitoring in several masonry buttresses of a historic building, as well as the assessment of the structural safety before, during, and after an intervention process. A brief analysis of the research is performed, and the motivation and the methodology adopted are described. Finally, the evolution of the measurements recorded and the analysis of the results achieved are detailed. The study enabled recommendations to be made to the intervening agents that guarantee structural safety.     

红茶菌发酵液清洗丝织文物表面结晶盐的应用研究

在我国考古出土的丝织品数量多,种类丰富,但由于墓葬环境的特殊性,如棺液的浸泡等原因,丝织文物的表面形成很多结块,影响了文物的品质。因此,对此类丝织文物的清洗成为文物保护工作的重要一环。为此,本研究以唐代出土丝织文物残片表面的结块为研究对象,利用拉曼光谱和X射线衍射仪检测技术对其表面结块的成分进行分析。结果表明,结晶盐的主要成分为CaSO4.2H2O。本研究针对其结晶盐的成分,再利用显微观察、抗拉强度检测等手段分析了红茶菌发酵液对老化的现代蚕丝影响。在得出没有损伤的基础上,利用红茶菌发酵液中的生物有机酸和生物酶作为生物清洗剂清洗唐代丝织文物残片表面的结晶盐,取得了良好的清洗效果,对丝织文物本身无损伤。     

Sonic Tomography for Masonry Walls Characterization

ABSTRACT

Nowadays, Sonic Pulse Velocity tests (SPV tests) are widely applied for detecting the morphology, hidden defects, and voids within structural elements. This technique, largely applied because non invasive and easy to perform, reveals particularly adapt in the case of ancient buildings, where usually any damage is not tolerated due to the historical preservation requirements. Moreover, recently the SPV tests have been also applied with tomography technology to obtain images of sonic speeds from which it is possible to rapidly reconstruct the internal elements morphology.

In this article, the results of some SPV tomographies regarding masonry elements are presented. The tests are carried out with the aim of establishing consistency and accuracy of this technique in determining the morphology of the investigated elements. The influence of investigation points number and noise smoothing is taken into account, too. At first, the results of a tomography derived from synthetic data of an ideal section are shown. Then, the SPV tomographies of some masonry specimens and of elements sections of a real case study are illustrated and compared among them.     

制备方法对土遗址重塑样稳定性的影响研究

土建筑遗址本体的保护受遗址土的物理、水理、力学及所处环境差异的影响，重塑样是替代土遗址测试其各种性质的重要手段，重塑样拌制土性质的稳定性是科学评价、对比分析试验研究的基础和前提。本研究基于不同拌制土的方法，通过观察、拍照、量取土团粒大小以及同条件制备样品的无侧限抗压强度等，综合评价不同拌制土方法的影响条件。研究发现，采用人工拌土、闷土时间在24 h的土所制的试样最具稳定性，随着闷土时间再增加，土样强度在逐渐降低。本研究为土建筑遗址室内试验研究和工程现场拌制土料提供理论参考和技术支撑。