This paper presents a comprehensive summary of data, analyses and findings from the investigations over the past twelve years about the relics of large Longyou rock caverns carved about 2 000 years ago at shallow dept...This paper presents a comprehensive summary of data, analyses and findings from the investigations over the past twelve years about the relics of large Longyou rock caverns carved about 2 000 years ago at shallow depths in argillaceous siltstone. The paper presents the typical features associated with the rock caverns. They include structures, large spans, portals, extreme shallow-buried depths, imprints, drainages, inclined ceiling, inclined sidewalls, slender rock pillars, rock staircases, site and strata selections, caving lighting, carving method, and underground construction surveying. They are used to reconstruct and highlight the design and construction methods adopted by the ancients. The paper further demonstrates that the relics of the complete large rock caverns are a consequence of coincidental combinations of ancient human effort and natural factors. The full occupation of water with weak acidity in the large rock caverns with the soft surrounding rocks of weak alkalinity is found to be the main factor ensuring and preserving the caverns to have been stable and integral over 2 000 years. However, the five unwatered complete rock cavern relics have been experiencing various deteriorations and small failures including cracks, seepage, small rock falls and delaminating ceiling rocks. Although these deteriorations have been repaired and stabilized effectively, the paper demonstrates that an entire roof collapse failure is highly possible in the near future to each of the five unwatered rock cavern relics. The findings presented in this paper are also invaluable both to the long-term protection and preservation of the large rock cavern relics of national and international interests and importance, and to extend and enrich our experience and knowledge on the long-term stability and integrity of man-made underground rock cavern engineering projects.展开更多
Five complete caverns were discovered in Longyou in 1992.They were manually caved in argillaceous siltstone at shallow depths more than 2000 years ago.When they were un-watered,their integrity was maintained completel...Five complete caverns were discovered in Longyou in 1992.They were manually caved in argillaceous siltstone at shallow depths more than 2000 years ago.When they were un-watered,their integrity was maintained completely,and their interior rock surfaces were free of old cracks.Since then,however,the rock's interior faces have initiated and propagated more and more cracks.This paper attempts to address the question of why the rock interior faces were free of old cracks once they were unearthed.To address this question,this paper proposes a hypothesis that the argillaceous siltstone has the ability of self-healing its cracks over a short period of time under weak acid water environment.Data and evidence are presented herewith to prove the hypothesis.They include observations and measurements in the field and test results in the laboratory.Specifically,a three-point bending test is used to form a tensile crack in a rectangular rock specimen and a deadload test for the specimen immersed in initially weak acid water is used for self-healing its crack.The results have shown that the argillaceous siltstone is in a state of weak alkalinity and the rain water at the site is in a state of weak acidity.Therefore,when it is immersed in weak acid water for some time,the argillaceous siltstone would be able to make chemical reactions to generate new minerals such as calcite.The new minerals would be able to infill the cracks and then heal the crack within a few years.Once the crack is self-healed,the rock can regain its strength and integrity.Consequently,the rock interior surfaces could be free of old cracks when the water was pumped out of the caverns.展开更多
基金Supported by the National Natural Science Foundation of China (40902088 and 40672190)the Key Project of Zhejiang Province Science and Technology (2007C23093)
文摘This paper presents a comprehensive summary of data, analyses and findings from the investigations over the past twelve years about the relics of large Longyou rock caverns carved about 2 000 years ago at shallow depths in argillaceous siltstone. The paper presents the typical features associated with the rock caverns. They include structures, large spans, portals, extreme shallow-buried depths, imprints, drainages, inclined ceiling, inclined sidewalls, slender rock pillars, rock staircases, site and strata selections, caving lighting, carving method, and underground construction surveying. They are used to reconstruct and highlight the design and construction methods adopted by the ancients. The paper further demonstrates that the relics of the complete large rock caverns are a consequence of coincidental combinations of ancient human effort and natural factors. The full occupation of water with weak acidity in the large rock caverns with the soft surrounding rocks of weak alkalinity is found to be the main factor ensuring and preserving the caverns to have been stable and integral over 2 000 years. However, the five unwatered complete rock cavern relics have been experiencing various deteriorations and small failures including cracks, seepage, small rock falls and delaminating ceiling rocks. Although these deteriorations have been repaired and stabilized effectively, the paper demonstrates that an entire roof collapse failure is highly possible in the near future to each of the five unwatered rock cavern relics. The findings presented in this paper are also invaluable both to the long-term protection and preservation of the large rock cavern relics of national and international interests and importance, and to extend and enrich our experience and knowledge on the long-term stability and integrity of man-made underground rock cavern engineering projects.
基金The authors would like to thank financial supports from the National Natural Science Foundation of China(Grant Nos.42272122 and 40902088).
文摘Five complete caverns were discovered in Longyou in 1992.They were manually caved in argillaceous siltstone at shallow depths more than 2000 years ago.When they were un-watered,their integrity was maintained completely,and their interior rock surfaces were free of old cracks.Since then,however,the rock's interior faces have initiated and propagated more and more cracks.This paper attempts to address the question of why the rock interior faces were free of old cracks once they were unearthed.To address this question,this paper proposes a hypothesis that the argillaceous siltstone has the ability of self-healing its cracks over a short period of time under weak acid water environment.Data and evidence are presented herewith to prove the hypothesis.They include observations and measurements in the field and test results in the laboratory.Specifically,a three-point bending test is used to form a tensile crack in a rectangular rock specimen and a deadload test for the specimen immersed in initially weak acid water is used for self-healing its crack.The results have shown that the argillaceous siltstone is in a state of weak alkalinity and the rain water at the site is in a state of weak acidity.Therefore,when it is immersed in weak acid water for some time,the argillaceous siltstone would be able to make chemical reactions to generate new minerals such as calcite.The new minerals would be able to infill the cracks and then heal the crack within a few years.Once the crack is self-healed,the rock can regain its strength and integrity.Consequently,the rock interior surfaces could be free of old cracks when the water was pumped out of the caverns.
