Stability monitoring and evaluation of the modeled test square for prehistoric earthen sites during excavation period

In order to explore the stability of test square during archaeological excavation for prehistoric earthen sites in Hangzhou, a modeled test square with 2. 3 min depth, inplane dimensions of 5 min width by 5 m in length, and an archaeological column in the middle was excavated by means of a top-down excavation technique. To investigate the stability performance of the modeled test square and the associated effect on the adjacent area, a real-time comprehensive instrumentation program was conducted during the excavation. Field observations included ground settlements, lateral displacement, pore pressure and underground water level. Monitoring data indicates that the ground settlement induced by dewatering and unloading action basically decreases with the increase of the distance away from the pit edge, and the lateral displacements at four sides showa nonlinear variation along the depth. The maximum value is far below the acceptable value regulated by the related standard,which validates the stability of the modeled test square during excavation. Variations of pore pressure and water level suggest that long-term stability should be paid more attention due to the slowconsolidation of soft soil. Meanwhile, it is proved that the step shape of the wall can resist lateral displacement more effectively than the vertical shape of wall. This case study provides insights into the real archaeological excavation in Hangzhou, in particular Liangzhu prehistoric earthen sites.

Nondestructive testing and assessment of consolidation effects of earthen sites

Earthen sites are widely distributed throughout China, and most of them belong to archaeological sites with significant values, which not only directly witness the origin, formation and development of Chinese civilization, but also possess important values for conservation and exhibition. Many researches and practices on their conservation and consolidation have been carried out; however, the consolidation effect is mainly judged by visual observation and expert evaluation. Scientific assessment of conservation and consolidation effects is a challenging issue. Many instruments in other fields cannot be directly applied to the conservation of cultural relics due to their peculiarity. In order to assess the effects of field conservation experiments, this paper tries to understand the consolidation effects at Liangzhu site using nondestructive or micro-damage methods, including thermo-physical parameters testing, infrared thermal imaging, high-density microelectrode resistivity testing, portable microscope observation, and hydrophilic and hydrophobic testing, and thereby explores the practicable methods for evaluating the properties of consolidation materials for earthen sites treatment.

Numerical simulation of the behaviors of test square for prehistoric earthen sites during archaeological excavation

During the process of archaeological excavation in the regions of Southeast China, collapse of test square usually occurs due to poor site-specific conditions. In this paper, the fast Lagrangian analysis of continua in three dimensions（FLAC3D） is employed to reveal the behaviors of test square. Taking the archaeological works in Liangzhu prehistoric earthen sites as the research background, the paper first introduces the geological setting, excavation procedure and monitoring scheme of the studied test square. Then, the deformation of four sides of the test square is modeled using FLAC3D. By comparison, it shows that the numerical results are consistent with the results from field monitoring. The result suggests that the numerical simulation can be effectively applied to representing the actual behaviors of the test square,which is helpful for determination of excavation scheme and stability evaluation of the test square during archaeological excavation.

Research progress on the development mechanism and exploratory protection of the scaling off on earthen sites in NW China

The scaling off is among the most pervasive and severe deterioration types.The scaling off developed on earthen sites in Northwest China has a special and complex binary structure composed of crusted and loose layers.Under the synergistic functions of external environmental elements such as rainfall,temperature,and wind,and rammed earth properties,this deterioration has gradually created the crust on the site’s surface,and has then evolved into exfoliation and finally fallen off,leading to the reciprocating progressive destruction of earthen sites.Therefore,determining the development mechanism of scaling off and implementing targeted protection measures for the scientific conservation of earthen sites has become essential.In this review study,the properties of the building material causing the binary structure and the coupling effects of water,temperature,salt,and wind on the development of scaling off were determined,and the quantitative evaluation system for this deterioration development was elaborated.After interpreting the reasons for the development of the scaling off,protective measures including chemical grouting,electro-osmosis grouting,and overlay applications were stated.This study also pointed out the research hotspots and shortage in the study process on the scaling off.The hotspots generally focused on the development mechanism of binary structure,quantitative assessment of the degree of development,and related scientific consolidation measures.The shortcomings around the above directions include less attention to the development characteristics and mechanism of scaling off on earthen sites under special environment types,optimization and applicability of quantitative evaluation models,and the development and feasibility of reinforcement slurries and methods.This study can be beneficial in providing theoretical support for the scientific conservation and engineering practice of the scaling off on the earthen sites.

Discussion on the environmental adaptability of weather-resistant measures for earthen sites in China

Earthen sites are important remains of past human societies.Weather-resistant measures comprise a major part of conservation eforts for earthen sites.Marked advancements in weather-resistant techniques have been made in recent years.Earthen sites are characterised by large numbers,large scales,various types,complex compositions,and diverse existing environments.Weather-resistant measures difer signifcantly in their environmental adaptability.The environmental adaptability of weather-resistant measures severely restricts further development and popularisation of weather-resistant technology at earthen sites.Based on the environmental and weathering characteristics of existing earthen sites in China,the consolidation and failure mechanisms of several weather-resistant measures(penetrating consolidation,sacrifcial layers,soft capping,protective structures,and backflling protection)were examined.The potential areas to increase the success of the diferent weather-resistant measures were obtained combined with the characteristics of various environmental boundaries.

Conservation of Jiaohe ancient earthen site in China

Earthen sites, which are mainly made of earth, are cultural heritages with historical, artistic and scientific values. Many extremely valuable earthen sites have been preserved in the arid areas in China. The earthen site of Jiaohe Ancient City is one of the earliest National Protected Important Cultural Heritage Sites. The Jiaohe Ancient City site exhibits all kinds of deteriorations, which can be found in the earthen sites in arid environments in China. Through a case study of the Jiaohe ancient earthen site, we present in this paper the comprehensive conservation technologies, including the mud bricklaying and reparation, wooden rod anchorage, crack grouting, surface potassium silicate （PS） penetration consolidation, and suspended steel beam ceiling, etc. Results of this case study showed that better conservation effects could be achieved by selecting proper PS penetration and crack grouting processes based on the deterioration characteristics of the earthen sites. The technology of mud bricklaying and reparation was also an effective method for preventing the earthen body from collapsing. Compared with traditional conservation technologies, the suspended steel beam ceiling technology could effectively reduce the negative impacts to the original state of the earthen site. As for unstable cliffs, a new method using composite anchor rod of bamboo and steel with massive loose earth was applied. Deformation monitoring and temporary supports were critical and indispensable measures for the safe of site conservation projects. Through years of monitoring and practical operation at the Jiaohe ancient earthen site, deterioration at the site has been effectively controlled.

A new inorganic-organic hybrid material as consolidation material for Jinsha archaeological site of Chengdu

An organic-inorganic epoxy-silica-acrylate(ESA) hybrid material was used for the consolidation of Jinsha archaeological site of Chengdu in China.The hybrid materials have multiple functional groups,such as anhydride,epoxy,hydroxyl and carboxyl,which can form networks at room temperature and result in an enhanced chemical and water resistance of the consolidated soil.With increasing of TEOS content,the hybrid materials keep colorless with only some reduction of transparency,while the hybrid materials obviously turn from moderate yellowish to brown yellow with the increase of the epoxy resin(EOR) content after 120 min UV irradiation.SEM observation indicates that the hybrid soil consolidation materials can effectively penetrate into the soil substrate,fill up most of the pores,decrease the area porosity and consolidate the Jinsha archaeological soil.The consolidation performances are in the sequence:ESA > K2SiO4(PS) > tetraethyl orthosilicate(TEOS).