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Du J.-G.,The Third Engineer Scientific Research Institute of the Headquarters of the General Staff | Guo S.-X.,The Third Engineer Scientific Research Institute of the Headquarters of the General Staff | Chen P.,Luoyang Ship Material Research Institute | Guo Q.-L.,Dunhuang Academy | And 2 more authors.
Yantu Lixue/Rock and Soil Mechanics | Year: 2017

The wall-paintings of Mogao Grottoes have suffered from cracks initiated under the influence of external micro-vibration environment for a long time. Therefore, it is necessary to study the mechanism of crack initiation in the wall-paintings, which provides scientific basis and technical support for the wall-paintings protection and repair. Tensile strength is obtained by experiments of four-point bending on the plaster ground of the wall-paintings. Digital image correlation technique is used to measure the strain variation and distribution in real time. Besides, the crack initiation on the plaster ground is analyzed when tensile damage occurrs to obtain the strain limit of the wall-paintings. Moreover, the influences of initial flaw, loading method and fatigue cycle number on the bearing capacity and the strain limit of the specimen are studied. The results show that the initiation of cracks and even their development to some extent will not affect the bearing capacity of the grottoes wall structure. The initial flaw of the plaster ground can increase the risk of cracking around the flaw. Fibers such as hemp improve the plaster ground with better plasticity and durability, and reduce cracks within the fatigue limit. In order to avoid crack occurrence, maximum normal strain of the plaster ground should be strictly controlled less than 0.40%. © 2017, Science Press. All right reserved.


Chen W.,CAS Institute of Geology and Geophysics | Li L.,Chinese Academy of Cultural Heritage | Li Z.,Dunhuang Academy | Zhao L.,Lanzhou University | And 2 more authors.
Construction and Building Materials | Year: 2017

The ginger nut has been used as building materials in Dadiwan site in Qin'an County, Gansu Province, China, and it was confirmed as the earliest lightweight concrete in China. However, the ginger nut is not a proper construction material because it does not contain cementitious components. In this paper, original ginger nut were calcined under different temperatures and the properties of the resultant modified ginger nut were analyzed. 1100 °C was chosen as optimal calcination temperature according to CaO, β-CaSiO3 and Ca2Al2SiO7 content. Based on mortar workability and strength as result of curing time, 0.33 was selected as the optimal water binder ratio of the ginger nut mortar. The results of the mechanical tests revealed that the mortar exhibited ductile behavior, and it is possibly due to the special structure between aggregates and hydration or carbonation products. Finally, several tests carried out to determine weathering resistance abilities of the ginger nut mortar showed that they will probably serve as restoration material for stone or soil relics. © 2017 Elsevier Ltd


Zhang H.-Y.,Lanzhou University | Yan G.-S.,Lanzhou University | Wang X.-D.,Dunhuang Academy
Journal of Zhejiang University: Science A | Year: 2012

Moisture adsorption-desorption tests (MATs) were conducted on simulated mural plaster specimens under different air temperatures (ATs) and relative humidity (RH) to investigate the possible effect of seasonal alteration and visitors' breath on the deterioration of Mogao Grottoes, Dunhuang, China. Saturated salt solutions were used to maintain a constant RH, and plant growth cabinets were used to maintain a constant or varying temperature in the simulation test. The weight of specimen was periodically measured to determine the adsorbed or desorbed moisture. Test data illustrate that the desorption process is far quicker than the adsorption one, indicating that it is possible to inhibit the disadvantage effect from visitors, such as shortening the staying time in caves. In case of high humidity, an accumulated moisture adsorption was found to correspond to the varying temperature. On the other hand, in case of low humidity, accumulated moisture desorption corresponded. Test data imply that opening caves more often to visitors in humid seasons should be avoided so as to prevent continuous wetting of wall paintings. © 2012 Zhejiang University and Springer-Verlag Berlin Heidelberg.


Mikayama A.,Kyoto University | Hokoi S.,Kyoto University | Ogura D.,Kyoto University | Okada K.,National Research Institute for Cultural Properties | Su B.,Dunhuang Academy
Energy Procedia | Year: 2015

The Mogao caves, which are designated as a World Heritage site, house the remains of one of the largest collections of Buddhist mural paintings. The cave investigated in this study is cave 285, which has paintings on the walls and ceiling. The purpose of this research is to identify the causes for the deterioration of the paintings, particularly on the east wall. Emphasis is placed on collision and adhesion of sand particles driven by the wind into the cave as a candidate cause of deterioration on the east wall. © 2015 The Authors.


PubMed | Tianjin University, University of Strathclyde and Dunhuang Academy
Type: | Journal: Scientific reports | Year: 2015

Although a significant amount of work has been performed to preserve the ancient murals in the Mogao Grottoes by Dunhuang Cultural Research, non-contact methods need to be developed to effectively evaluate the degree of flaking of the murals. In this study, we propose to evaluate the flaking by automatically analyzing hyperspectral images that were scanned at the site. Murals with various degrees of flaking were scanned in the 126th cave using a near-infrared (NIR) hyperspectral camera with a spectral range of approximately 900 to 1700nm. The regions of interest (ROIs) of the murals were manually labeled and grouped into four levels: normal, slight, moderate, and severe. The average spectral data from each ROI and its group label were used to train our classification model. To predict the degree of flaking, we adopted four algorithms: deep belief networks (DBNs), partial least squares regression (PLSR), principal component analysis with a support vector machine (PCA+SVM) and principal component analysis with an artificial neural network (PCA+ANN). The experimental results show the effectiveness of our method. In particular, better results are obtained using DBNs when the training data contain a significant amount of striping noise.


Liang H.,Nottingham Trent University | Lucian A.,Nottingham Trent University | Lange R.,Nottingham Trent University | Cheung C.S.,Nottingham Trent University | Su B.,Dunhuang Academy
ISPRS Journal of Photogrammetry and Remote Sensing | Year: 2014

PRISMS (Portable Remote Imaging System for Multispectral Scanning) is designed for in situ, simultaneous high resolution spectral and 3D topographic imaging of wall paintings and other large surfaces. In particular, it can image at transverse resolutions of tens of microns remotely from distances of tens of metres, making high resolution imaging possible from a fixed position on the ground for areas at heights that is difficult to access. The spectral imaging system is fully automated giving 3D topographic mapping at millimetre accuracy as a by-product of the image focusing process. PRISMS is the first imaging device capable of both 3D mapping and spectral imaging simultaneously without additional distance measuring devices. Examples from applications of PRISMS to wall paintings at a UNESCO site in the Gobi desert are presented to demonstrate the potential of the instrument for large scale 3D spectral imaging, revealing faded writing and material identification. © 2014 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS).


Zhang J.-K.,Lanzhou University | Chen W.-W.,Lanzhou University | Li Z.-X.,Dunhuang Academy | Guo Q.-L.,Dunhuang Academy | Sun M.-L.,Northwest University, China
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2015

To scientifically reveal the characteristics of the setting and long-term performance of PS-(C+F) slurry which is applied in the anchoring conservation of earthen sites, the slurry with the optimum mix ratio (0.39) is studied by means of aging strength, aging moisture, aging wave velocity and shrinkage tests, and its durability is investigated by using the temperature-humidity cycling, frozen-thaw cycling, water stabilizing, soundness and alkali resistivity tests. The test results indicate that the aging strength can firmly meet the requirements of the anchoring craft, and that the elastic-fragile mechanical performance of the slurry is compatible to the earthen sites on the appearance, density, void ratio and strength. Furthermore, the very low shrinkage guarantees the interfacial mechanical property. Besides them, the consolidation has a strong durability to resist the arid and semi-arid climate in Northwest China. However, the slurry is not suitable for the earthen sites with high-content sodium sulphate. In conclusion, with strong compatibility and durability, the PS-F slurry with mix ratio of (C∶F=1, PS∶( C+F) =0.39) can satisfy the need of the anchoring conservation of earthen sites in Northwest China. ©, 2015, Chinese Society of Civil Engineering. All right reserved.


Zhang H.-Y.,Lanzhou University | Wang X.-D.,Lanzhou University | Wang X.-D.,Dunhuang Academy | Lu Q.-F.,Lanzhou University | Zhang Y.-J.,Lanzhou University
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

The bamboo-steel cable composite anchor (BSCC anchor) is a new anchor with phyllostachys heterocyclavar as pipe material, and was applied to reinforce earthen ruins bequeathed on the ancient silk road in Northwest China, which can get high anchorage strength due to its big cross-section. Field test illustrated that the failure of BSCC anchor was characterized by pulling-out of steel strand from inner binder. In order to understand the working mechanism between inner binder and steel strand, laboratory tests were conducted on four species of specimens, to investigate the bond-slip property between them. The test results indicate that there are three stages for the bond-slip process between inner binder and steel strand which are exponential-enhancing stage, softening-declining stage and residual stress stage. Moreover, the length of softening-declining stage is short, and the bond-slip process can be described by a simplified model and an exact model. It is found that the shear stress is not uniform distributing between the interface of inner binder and steel strand; and it approaches a peak near the loading end; and the peak stress increases and shifts far further from the loading end when pulling load is increased. The average shear stress between inner binder and steel strand, submits exponential decay regularity, and decreases along with the anchor length during the bond-slip process. It acquires the differential equation of bond-slip through theory analysis, and the variation rules of the axial force of steel strand and relative displacement between the interface of inner binder and steel strand. From results, it is found that the axial force of steel strand and relative displacement decrease along with the anchor length; and the results can be used for anchor design and application.


Wu J.,Dunhuang Academy | Yu T.,Dunhuang Academy | Zhao L.,Zhejiang University
Proceedings - 2013 4th World Congress on Software Engineering, WCSE 2013 | Year: 2013

We present a novel approach called Uniform Sample Compositing (USC) to improve the efficiency of gradient-domain compositing of large image, which could be implemented in significantly reduced time and memory. Firstly, our algorithm divides an original source image into many quadrilateral patches, and discards inner pixels and reserves the border pixels of patches) to constitute two low resolution images (Uniform-Sample-images) on which the image compositing operator is implemented. Finally according to the solution of Uniform-Sample-images the result image is evaluated by concurrently computing inner pixels of every quadrilateral patch on GPU. The evaluation of these patches is independent to each other so that our algorithm has better parallelism. The reduction of time and memory is achieved by solving Poisson equation on low resolution and inner interpolation on quadrilateral patches. The major merits of our approach are demonstrated by performing large image composite (whose size is about multi-Gigabyte) in significantly reduced time and memory while achieving visually identical results. © 2013 IEEE.


Shao M.-S.,Lanzhou University | Li Z.-X.,Lanzhou University | Li Z.-X.,Dunhuang Academy
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2011

SEM was employed to analyze the micropore structure of remolded samples which were reinforced by PS or not. The effects of clay mineral, pore structure and shrinkage on the soil-water characteristic curve (SWCC) of remolded unsaturated clay after consolidating by PS were analyzed. The results show that PS can improve the mechanical property through binding separate earthen relics particle together, and a series of physical and chemical reactions between PS and particle surface also improve the clay behaviors of the remolded unsaturated clay, such as pore structure, psephicity and shrinkage, which lead to the change of SWCC of the unsaturated clay. The results also suggest that the characters of the samples including saturated water content, residual water content, air entry value and the slope of the SWCC are changed after consolidating by PS, the saturated water content and residual water content are lower while the air entry value and the slope of the SWCC become higher than that without PS. Van Genuchten model (i.e., VG model) fits the experimental data well. The conclusion proves the good performance of PS consolidation for earthen sites well.

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