Abstract
Tianluoshan site (5000∼2500 BC), which belongs to the Hemudu culture, has suffered damages from the hydraulic effect like other Chinese earthen sites in moist circumstance. Tung oil and sticky rice juice, as Chinese traditional building materials, were chosen as the additives in this study. Tung oil has the property of good waterproofness, fast dry-up, and quick film-forming by oxidation. Sticky rice juice has the advantage of high glutinousness, good tenacity, and low expandability. The study is to figure out the best performing mixture of tung oil and sticky rice juice to decrease the permeability of soil and increase its strength to facilitate excavations at archeological sites enlarging the display of layers of cultures. Meanwhile, the color of the site soil after reinforcement must be maintained for a long time. From the direct shear tests and the falling head test of 9 specimens mixed in different mass ratios, it was confirmed that the optimal mass ratio of the tung oil, the sticky rice juice, and the soil was 5 : 10 : 85. The treated soil specimen of the optimal mass ratio had the largest increment of shearing strength. The self-standing height of the vertical soil wall increases correspondingly from 2.63 m to 6.18 m, which could enlarge the step height when excavating a deep earthen site and extend the display height at the protection stage. The treated soil at the optimal mass ratio also showed the largest decrement of permeability coefficient from 1.257 × 10−5 cm/s of the untreated soil to 1.627 × 10−6 cm/s, which could reduce the hydraulic effect to the soil. The microstructures of the 9 specimens in different mass ratios were observed by SEM. The results showed that the glutinousness of sticky rice juice could cohere soil particles together, and the tung oil could then form oxidation film wrapping around the particle groups. In order to meet the aesthetic requirements of earthen sites conservation, the surface color contrast tests were used to measure the color change induced by the two additives. The surface contrast tests showed that the treated soil at the optimal mass ratio had the minimum variation of the surface, which could satisfy the basic requirements of earthen sites protection.
Highlights
In China, many immoveable historical earthen sites are facing severe threat due to the natural environment and human activities, such as shrinkage, cracking, collapse, and erosion [1, 2]
According to air humidity or soil water content, the historical earthen sites are commonly divided into dry or moist earthen sites at present [3]. ereupon, the damages of the historical earthen sites in dry or moist states in China present regional differences on account of the climate variation in different zones [4]. e research of conserving methods applied to the dry earthen sites is much more mature than to the moist earthen sites [5]. us, it is imperative and necessary to conduct the research of conserving methods applied to the moist earthen sites
Distinct differences exist in the protective measures between the earthen sites conservation and the modern foundation engineering [7]. e materials used in earthen sites to improve the property of soil mass are forbidden to change the appearance of soil mass and bring about other damages [8]
Summary
In China, many immoveable historical earthen sites are facing severe threat due to the natural environment and human activities, such as shrinkage, cracking, collapse, and erosion [1, 2]. Seepage is the most important factor, which leads to much more severe damages [6] It is of great significance and urgency to figure out how to strengthen the soil mass and increase the resistance of the hydraulic effect to protect the earthen sites. A large-scale reinforced concrete has been commonly used to reduce the permeation and increase the strength of the soil in modern foundation engineering, while could not be used in the conservation of historical earthen sites. Most of the existing studies have shown that tung oil and sticky rice juice can provide good effects of reinforcement, respectively, along with other additives. There have been few studies to examine the improved effects by the mixture of tung oil and sticky rice juice together. This study focused on the improvement of the silt soil provided by the sticky rice juice and tung oil. The surface color contrast tests were conducted to make sure the treatment of tung oil and sticky rice juice could maintain the aesthetic surface color
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