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Zhang J.,Lanzhou University | Zhang J.,National Research Center for Conservation of Ancient Wall Paintings | Chen W.,Lanzhou University | Chen W.,National Research Center for Conservation of Ancient Wall Paintings | And 4 more authors.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2014

The field experiment was carried out in Jiaohe ruins(the largest earthen sites of the world), and two bolts with different lengths were pulled out according to the requirement of the basic experiment, meanwhile, strain monitoring points were set up along the interfaces of the bolts. The results show that the bolt of 8 m can get the anchorage force of 408 kN, which meets the conservation demand of large-scale earthen sites; with the increase of the bolt length, the maximum anchorage force increases and the average anchorage force decreases. There are single-peak and multi-peak distributions in the interfaces along the bolt. With the increase of the load, interfacial shearing stress increases and transfers to the end of the bolt as well as the peak shearing stress of the interface; the condition transformation of shearing stress takes place under large load during experiment.

Zhang D.,Shanghai JiaoTong University | Wang T.,Shanghai JiaoTong University | Wang X.,Conservation Institute of Dunhuang Academy | Wang X.,National Research Center for Conservation of Ancient Wall Paintings | And 2 more authors.
Engineering Geology | Year: 2012

As a new kind of inorganic reinforced material, potassium silicate can greatly improve the mechanical strength and the anti-wind erosion ability of ruins' soil in arid areas after being reinforced. The research developed a test device and test method of determining the thermal conductivity of earthen ruins' soil. The disturbed soil taken from the site of Jiaohe Ruins was made into soil specimens, and then, to study the reinforcement effect PS has on the thermal conductivity of ruins' soil by a thermal conductivity determination test and a laboratory model test. Test analysis showed that the thermal conductivity of PS reinforced specimens was reduced, furthermore, the larger the PS concentration, the smaller the thermal conductivity. Because PS decreased the soil's thermal conductivity, the heat transfer process of the reinforced soil was changed, and when external temperature had a change, the PS reinforced soil had a slower response to temperature than the unreinforced soil. From the analysis above, it is known that PS reinforced soil can slow down the physical weathering caused by temperature difference. And this viewpoint provides very useful scientific basis for studying the mechanism of PS and the earthen ruins' soil in northwest China arid regions. © 2011 Elsevier B.V.

Zhao L.-Y.,Lanzhou University | Zhao L.-Y.,National Research Center for Conservation of Ancient Wall Paintings | Li L.,Chinese Academy of Cultural Heritage | Li Z.-X.,Lanzhou University | And 2 more authors.
Wuji Cailiao Xuebao/Journal of Inorganic Materials | Year: 2011

Silicate is one of the most typical materials in both traditional and modern buildings. A comparative analysis on two silicate materials (ginger nut and Aga soil) used in the ancient buildings of China was presented. The research suggests that ginger nut and Aga soil have similar chemical composition and physical properties. After they are calcined at 700-1400°C, they will have a combining characteristic of hydraulicity and nonhydraulicity. As the calcinations temperature rises, the nonhydraulic constituent is firstly increased and then decreased, and the hydraulic constituent is increasing regularly. Both chemical compositions and characteristics of the calcined ginger nut and Aga soil are similar to those of the "Hydraulic lime" in Europe. Thus the properties change of ginger nut and Aga soil can be used for repairing and reinforcing the stone, earthen, brick and ceramic relics.

Li Z.,Lanzhou University | Li Z.,National Research Center for Conservation of Ancient Wall Paintings | Zhao L.,Lanzhou University | Zhao L.,National Research Center for Conservation of Ancient Wall Paintings | Li L.,Chinese Academy of Cultural Heritage
Science China Technological Sciences | Year: 2012

During 1970s, the residential remains of the Yangshao Period were discovered at the Dadiwan site in Qin'an County, Gansu Province, China. With carbon-14 dating, scanning electron microscope (SEM), thermal expansion analyzer, polarizing microscope (PLM), and X ray diffraction (XRD), the microstructures and chemical compositions of the pottery shard, floor materials of the housing site, kunkur, calcined kunkur, ginger nut (calcium concretion) from the Dadiwan site were analyzed and researched. Analysis and simulation tests were also carried out to study the hydratability of calcined ginger nut and calcined kunkur, and the manufacturing process of the residential floors. The research shows that the floor was made of a light concrete formed by the mixture of aggregate of calcinated ginger nut (locally deposited), red clay and kunkur. The dicalcium silicate (C 2S) from the floor material of the housing site is one of the main constituents of modern cement, and the floor is also similar to modern concrete in nature. Therefore, the floor material of the housing site at the Dadiwan site was the earliest man-made concrete in the world ever discovered. © Science China Press and Springer-Verlag Berlin Heidelberg 2012.

Li H.,The Conservation Institute of Dunhuang Academy | Li H.,National Research Center for Conservation of Ancient Wall Paintings | Wang W.,The Conservation Institute of Dunhuang Academy | Wang W.,National Research Center for Conservation of Ancient Wall Paintings | And 6 more authors.
Geomorphology | Year: 2014

A survey found that sand wedges are widely distributed in the extremely extra-arid Gobi region of Dunhuang, China. The sand wedges are still developing. Well-developed sand wedges are surrounded by polygonal areas showing fractal structures. The depth of a well-developed sand wedge is 50-60. cm and its maximum width is 50-60. cm, so the depth/width ratio is 1.0. The interface between the wedge and matrix is arc-shaped. The mechanical composition of the sand wedges compared to the matrix is such that 76.72% of the particles have diameters ≤. 0.25. mm and show vertical sand laminations in the sand wedge, while 55.19% of the particles in the matrix are ≥. 2.00. mm in diameter. The particle diameters are consistent with the width of the sand-wedge fractures. The salt content in the sand wedges is 3.13. g/kg, while that of the matrix is 40.86. g/kg. The large salinity difference shows that the sand in the wedges comes from drift sand or cladding layers where salinity is lower, and that the sand wedge was formed in an arid climate. Displacement and pressure are closely associated with the daily temperature variation; they fluctuate significantly following the temperature. Measurements reveal the movement of thermal-contraction fissures. Pressure monitoring identified that wet expansions occurred after rainfall, which made the sand wedges become tightly joined to the matrix. Following this, as the soil became desiccated and shrank, a crack opened in the middle of the sand wedge. This was then filled with drift sand. With the next rainfall, the system moved into another development cycle. The current article reveals a new mechanism for forming sand wedges in extra-arid conditions. Arid sand wedges are a unique drought-induced surface landmark resulting from long-term, natural, dry-climate processes. © 2014 Elsevier B.V.

Zhang J.-K.,Lanzhou University | Zhang J.-K.,National Research Center for Conservation of Ancient Wall Paintings | Chen W.-W.,Lanzhou University | Chen W.-W.,National Research Center for Conservation of Ancient Wall Paintings | And 4 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

The researches on anchorage mechanism of wood bolts are of great value to the excavation of traditional materials and crafts and the current conservation of earthen sites. Taking a typical earthen site (Jiaohe ruins) as an example, field anchorage tests are carried out, including survey of anchorage performance and monitoring of shear strain on the first interface (bolt vs. grout) of the anchorage system. The test results shows that (1) there are huge differences among wood bolts due to their natural selection, however, the anchorage can afford enough forces; (2) during loading, the shear stress varies non-uniformly with peaks along the interface; (3) with the increase of the load, the peak of shear stress shifts gradually toward the end of bolt; (4) apparent shearing expansion improves anchorage performance; and (5) the anchorage of wood bolts exhibits the features of tension-type and compression-type.

Wang X.-D.,Lanzhou University | Wang X.-D.,National Research Center for Conservation of Ancient Wall Paintings | Guo Q.-L.,Lanzhou University | Guo Q.-L.,National Research Center for Conservation of Ancient Wall Paintings | And 4 more authors.
Yantu Lixue/Rock and Soil Mechanics | Year: 2010

Influenced by the material and natural environment, the wall paintings of Dunhuang Mogao grottoes have many diseases: flaking, disruption, detachment and loss; and many researches have proved that these diseases are caused by moving of salts; however the moisture is the main factor for the activation and moving of the salt. So, research on rock permeability of the Mogao Grottoes can explain regulations of water migrations and help us to learn the mechanism of wall painting deterioration. This article adopted the test of designated water level in situ to get the permeation coefficient of different groups of surrounding rocks, the test of high-intensively resistivity permeation monitoring in situ experiments; X-Ray CT account the void ratio to study the permeability of the surrounding rocks. We know that different rock strata of Mogao Grottoes have different permeabilities; even the rocks from the same stratum have very different permeability coefficients. Some stratum with good permeability makes it possible that the water permeates inside the cave through the rock layers. Due to the particularity of culture relics and some other reasons, high-density electric resistivity method and X-Ray CT scanning are efficient ways to learn the permeability of surrounding rocks under the situation that we can't measure it directly.

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