Consolidation effect of composite materials on earthen sites

Significance 

Based on statistics provided by UNESCO, earthen ancient and traditional sites account for about 10% of the world’s cultural heritage. Unfortunately, of the world’s endangered heritage, these earthen sites make up 57%. Generally, as earth by itself is not a resilient material, continuous exposure to recurrent decay, such as; surface stripping, fissures, gullies, and collapses, has left majority of these sites in a deplorable state. For instance, in China, the Great Wall has undergone severe decays subject to variations in humidity and temperature, hence threatening its durability and preservation. Soil has low mechanical strength hence high solubility in water. Consequently, this reduces the stability of the wall. Therefore, it is imperative to reinforce and repair soil ruins. Several consolidation techniques have over the years been proposed to rehabilitate soil failures. Recently, weather resistant consolidating materials have gained interests. Unfortunately, as there is no single consolidation product that is universally applicable for the protection of earthen sites, there is need to assess the suitability of combined consolidation products, using simple and practical methods for heritage consolidation.

In this view, a team of researchers led by Dr. Wenwu Chen from the School of Civil Engineering and Mechanics, Lanzhou University conducted thorough study in which a comparison of the effectiveness of single and composite materials was undertaken with the purpose of establishing whether composite materials were potential candidates for use in conservation. Particularly, they focused on assessing various consolidation treatments so as to determine the suitability of composite materials for future use in the consolidation of earthen sites. Their work is currently published in the research journal, Construction and Building Materials.

The authors first, considered developing a composite composed of organic and inorganic materials in different orders based on existing materials. Soils from the Great Wall of Yongchang, Gansu Province, China, were treated with five types of materials, namely, inorganic materials, organic products, composite materials composed of organic and inorganic materials in different orders, and ethanol. Changes in the color, weight, mechanical properties, water resistance, microstructures, and element composition were evaluated after treatment. Finally, synthetic evaluation was conducted using the obtained results.

The researchers observed that Better reinforcing effects were obtained by applying an organic material and then using an inorganic material. In addition, they noted that the consolidation effect of inorganic materials was much weaker than those of the composites. Compared with organic materials, organic + inorganic composites exhibited a much lesser change in color, and improved compatibility in appearance of the organic materials. Other results indicated that organic + inorganic composite materials with half the amount of organic materials and half the consumption of inorganic materials yielded obviously enhanced surface hardness, P-wave velocity, unconfined compressive strength, and water resistance.

In summary, Dr. Wenwu Chen and colleagues presented results of laboratory tests conducted on six groups of samples, in a bid to analyze the differences in the strengthening performance between composite and traditional single materials. Based on experiments conducted, the obtained results proved that the consolidation effect of certain composites was better than that of single materials. Altogether, more work considering other parameters such as wind effects, temperature and humidity is necessary as this study was exclusively done under controlled laboratory environment.

Surface stripping on the Great Wall - Advanced Engineering
Fig. 1. Surface stripping on the Great Wall
Location of the Great Wall of the Ming Dynasty in Gansu Province, China - Advanced Engineering
Fig. 2. Location of the Great Wall of the Ming Dynasty in Gansu Province, China
Machine for remoulding samples - Advanced Engineering
Fig. 3. Machine for remoulding samples
(a) Micron lime; and (b) ethyl silicate
Fig. 4. (a) Micron lime; and (b) ethyl silicate
Photographs of the samples after curing for 28 days - Advanced Engineering
Fig. 5. Photographs of the samples after curing for 28 days
Weight changes during the curing period - Advanced Engineering
Fig. 6. Weight changes during the curing period
Surface hardness as a function of curing period - Advanced Engineering
Fig. 7. Surface hardness as a function of curing period
Compression wave velocity of the specimens before reinforcement and after curing for 28 days - Advanced Engineering
Fig. 8. Compression wave velocity of the specimens before reinforcement and after curing for 28 days
Disintegration process: (a) 0 s; (b) 10 s; (c) 30 s; (d) 60 s; (e) 120 s; (f) 300 s; (g) 600 s; (h) contrast between BM+BE and BE; (i) 1 day - Advanced Engineering
Fig. 9. Disintegration process: (a) 0 s; (b) 10 s; (c) 30 s; (d) 60 s; (e) 120 s; (f) 300 s; (g) 600 s; (h) contrast between BM+BE and BE; (i) 1 day
SEM-EDS images of the soils, 500: (a) surface of samples treated with BE+BM; (b) interior of samples treated with BE+BM; (c) untreated samples - Advanced Engineering
Fig. 10. SEM-EDS images of the soils, 500: (a) surface of samples treated with BE+BM; (b) interior of samples treated with BE+BM; (c) untreated samples

About the author

Wenwu Chen

Professor

School of Civil Engineering and Mechanics
Lanzhou University, 222 Tianshui South Road, Lanzhou, Gansu 730000, China

Ph: 0931-8914308, Fax: 0931-8914308, Email: sungp.AT.lzu.edu.cn

Education

Ph.D., Lanzhou University, Geological Engineering, 2004

M.E., Lanzhou University, Geological Engineering, 1992

B.E., Lanzhou University, Geological Engineering, 1989

Professional Experience

Professor, 2002-present
Associate Professor, 2000-2002
Lecturer, 1995-2000
Teaching Assistant, 1992-1995

Research Fields

Cultural heritage conservation, Loess Landslide, Geotechnical Engineering

Professional Service

Committee Member, Geological Teaching Steering Committee of the Ministry of Education, 2013-present

Secretary General, International Society of Rock Mechanics, Professional Committee for Ancient Site Protection, 2013-present

Vice Chairperson, China Society of Rock Mechanics and Engineering Ancient Site Protection and Reinforcement Engineering Committee, 2008-present

Director, Chinese Society of Rock Mechanics and Engineering, 2002-present

Committee Member, Engineering Geology Committee of China Geological Society, 2004-present

Member of International Association of Engineering Geology and Environment, 2004-present

Committee Member, Committee of Investigation and Geophysics, China Association, 2005-present

Director, China Architectural Society of China, 2014-present

Major Academic Achievements, Awards and Honors

Professor Wenwu Chen has hosted more than 70 international cooperation, national, ministries and other horizontal projects, won more than 10 awards at the national and provincial level, and published more than 100 papers.

Publications

  1. Chen Wenwu*, Zhang Yingmin, Zhang Jingke, et al. Consolidation effect of composite materials on earthen sites[J]. Construction and Building Materials, 2018, 187: 730-737.

  2. Chen Wenwu*, Guo Zhiqian, Zhang Jingke, et.al. Evaluation of Long-Term Stability of Mogao Grottoes Caves under Enhanced Loading Conditions of Tourists[J]. Journal of Performance of Constructed Facilities, 2018, 32(4), August 1.

  3. Shen Yunxia, Chen Wenwu*, Kuang Jing, et al. Effect of salts on earthen materials deterioration after humidity cycling[J]. Journal of Central South University, 2017, 24(4): 796-806.

  4. Chen Wenwu*, Yang Guang, Zhang Yingmin, et al. Effect of Moss Soil Crust on the Scaling Off of Earthen Sites in Qinghai[J]. Advanced Engineering Sciences, 2017, 49(5): 22-27 (in Chinese)

  5. Chen Wenwu*, Dai Pengfei, Yuan Pengbo, et al. Effect of inorganic silicate consolidation on the mechanical and durability performance of sandstone used in historical sites[J]. Construction and Building Materials, 2016, 121: 445-452.

  6. Guo Zhiqian, Chen Wenwu*, Zhang Jingke, et al. Hazard assessment of potentially dangerous bodies within a cliff based on the Fuzzy-AHP method: a case study of the Mogao Grottoes, China[J]. Bulletin of Engineering Geology and the Environment, 2016, 1-12.

Reference

Wenwu Chen, Yingmin Zhang, Jingke Zhang, Pengfei Dai. Consolidation effect of composite materials on earthen sites. Construction and Building Materials, volume 187 (2018) page 730–737.

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