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| Vacuum preloading sealing performance and field test of soft soil foundations with silty sand layer |
| FU Hongtao1，2，3，4，WANG Xiaofeng1，WEN Zuojia1，GAO Ziyang1，2，5，WANG Jun1，2，3，4，LI Xiaobing1，2，3，4，YE Shuxiang6，LIN Zhongzhe6 |
| (1. College of Civil Engineering and Architecture，Wenzhou University，Wenzhou，Zhejiang 325035，China；2. Key Laboratory of Engineering and Technology for Soft Soil Foundation and Tideland Reclamation of Zhejiang Province，Wenzhou University，Wenzhou，Zhejiang 325035，China；3. Zhejiang Engineering Research Center of Disaster Prevention and Mitigation for Coastal Soft Soil Foundation，Wenzhou University，Wenzhou，Zhejiang 325035，China；4. Collaborative Innovation Center of Tideland Reclamation and Ecological Protection，Wenzhou University，Wenzhou，Zhejiang 325035，China；5. International Cooperation Base for Science and Technology on Ultra-soft Soil Engineering and Smart Monitoring，Wenzhou University，Wenzhou，Zhejiang 325035，China；6. Wenzhou Education Bureau，Wenzhou Education Infrastructure Center，Wenzhou，Zhejiang 325035，China) |
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Abstract When using vacuum preloading for soft soil foundations that contain high permeability sand layers，it is effective to establish a clay sealing wall to maintain the integrity of the vacuum system. The silt mixed with silt forms a flocculent structure at a microscopic level，which significantly affects the soil permeability when subjected to external disturbance. Experiments were conducted to determine the relationship between soil permeability coefficient(kv)，effective stress(?′)，and clay content(Nc). This relationship can be used as a basis for evaluating the construction of sealing walls. Subsequently，field tests were conducted on this type of foundation with different PVD spacing. The test results revealed that the permeability coefficient of silty sand and silt is less than 10－5 cm/s，considering the effect of ?′. The vacuum pressure under the membrane was maintained at around 83 kPa，indicating good sealing performance of the vacuum system and suggesting that a sealing wall is unnecessary for this type of foundation. After reinforcement，the moisture content is reduced by 20% and the void ratio of silt is reduced by 30%. The vane shear strength increased by 22.3–32.23 kPa.
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[1] 中华人民共和国行业标准编写组. JTS147—2—2009真空预压加固软土地基技术规程[S]. 天津：人民交通出版社，2009.(The Professional Standards Compilation Group of People?s Republic of China. JTS147—2—2009 Technical specification for vacuum preloading reinforcement of soft soil foundation[S]. Tianjin：People?s Communications Press，2009.(in Chinese))
[2] 胡利文，王永平. 真空预压淤泥搅拌墙气密性试验分析与应用技术[J]. 岩土力学，2005，26(3)：427–431.(HU Liwen，WANG Yongping. Test study and application technique for airtight capacity of mixing silt wall under vacuum preloading[J]. Rock and Soil Mechanics，2005，26(3)：427–431.(in Chinese))
[3] CHAI J C，JOHN P CARTER，MARTIN D LIU. Vacuum consolidation and deformation analyses – case studies in Japan[C]// Proceedings of the International Conference on Ground Improvement and Ground Control. [S. l.]：[s. n.]，2012：307–319.
[4] TANG M，SHANG J Q. Vacuum preloading consolidation of Yaoqiang Airport runway[J]. Géotechnique，2000，50(6)：613–623.
[5] 刘增荣，刘春原，梁 波. 土力学[M]. 上海：同济大学出版社，2005：20–21.(LIU Zengrong，LIU Chunyuan，LIANG Bo. Soil mechanics[M]. Shanghai：Tongji University Press，2005：20–21.(in Chinese))
[6] BELKHATIR M，SCHANZ T，ARAB A. Effect of fines content and void ratio on the saturated hydraulic conductivity and undrained shear strength of sand–silt mixtures[J]. Environmental Earth Sciences，2013，70(6)：2 469–2 479.
[7] 孔令伟，李新明，田湖南. 砂土渗透系数的细粒效应与其状态参数关联性[J]. 岩土力学，2011，32(增2)：21–26.(KONG Lingwei，LI Xinming，TIAN Hunan. Effect of fines content on permeability coefficient of sand and its correlation with state parameters[J]. Rock and Soil Mechanics，2011，32(Supp.2)：21–26.(in Chinese))
[8] ONG C Y，CHAI J C，HINO T. Degree of consolidation of clayey deposit with partially penetrating vertical drains[J]. Geotextiles and Geomembranes，2012，34：19–27.
[9] CAI Y Q，XIE Z W，WANG J，et al. New approach of vacuum preloading with booster prefabricated vertical drains(PVDs) to improve deep marine clay strata[J]. Canadian Geotechnical Journal，2018，55(10)：1 359–1 371.
[10] 中华人民共和国国家标准编写组. GB 50021—2001 岩土工程勘察规范[S] 北京：中国建筑工业出版社，2009.(The National Standards Compilation Group of People?s Republic of China. GB 50021—2001 Code for investigation geotechnical engineering[S]. Beijing：China Construction Industry Press，2002.(in Chinese))
[11] 曹圣华. 滨滩相互层土工程特性初步研究[J]. 地质学刊，2010，34(1)：61–66.(CAO Shenghua. A preliminary study on engineering characters of interbedded soils in littoral and river facies[J]. Journal of Geology，2010，34(1)：61–66.(in Chinese))
[12] TANAKA H，OKA F，YASHIMA A. Sampling of soft soils in Japan[J]. Marine Georesources and Geotechnology，1996：14(3)：283–295.
[13] 中华人民共和国国家标准编写组. GB/T 50123—2019 土工试验方法标准[S]. 北京：中国建筑工业出版社，2019.(The National Standards Compilation Group of People?s Republic of China. GB/T 50123–2019 Standard for test method[S]. Beijing：China Construction Industry Press，2019.(in Chinese))
[14] 崔先泽，文 韬，李志祥，等. 水位波动下砂层中颗粒运移及沉积特性试验研究[J]. 岩土工程学报，2024，46(5)：1 094–1 101.(CUI Xianze，WEN Tao，LI Zhixiang，et al. Retention and transport behavior of silicon micropowder in sand under periodical water level fluctuations[J]. Chinese Journal of Geotechnical Engineering，2024，46(5)：1 094–1 101.(in Chinese))
[15] 王 军，蔡袁强，符洪涛，等. 新型防淤堵真空预压法室内与现场试验研究[J]. 岩石力学与工程学报，2014，33(6)：1 257–1 268. (WANG Jun，CAI Yuanqiang，FU Hongtao，et al. Indoor and field experiment on vacuum preloading with new anti-clogging measures[J]. Chinese Journal of Rock Mechanics and Engineering，2014，33(6)：1 257–1 268.(in Chinese))
[16] WANG J，CAI Y Q，NI J F，et al. Effect of sand on the vacuum consolidation of dredged slurry[J]. Marine Georesources and Geotechnology，2018，36(2)：238–244.
[17] 吴子龙，朱向阳，邓永锋，等. 砂–黏土混合物的压缩性状及其粗颗粒骨架形成机制[J]. 土木工程学报，2016，49(2)：121–128.(WU Zilong，ZHU Xiangyang，DENG Yongfeng，et al. Compression behavior of sand-clay mixtures and formation mechanism of coarse granulesand skeleton[J]. China civil Engineering Journal，2016，49(2)：121–128.(in Chinese))
[18] CHU J，YAN S W. Estimation of degree of consolidation for vacuum preloading projects[J]. International Journal of Geomechanics，2005，5(2)：158–165.
[19] BELKHATIR M，ARAB A，DELLA N，et al. Experimental study of undrained shear strength of silty sand：effect of fines and gradation[J]. Geotechnical and Geological Engineering，2012，30(5)：1 103–1 118.
[20] 中华人民共和国行业标准编写组. JTS 147–1–2010 港口工程地基规范[S]. 北京：中国建筑工业出版社，2010.(The Professional Standards Compilation Group of People?s Republic of China. JTS147–1–2010 Foundation Specifications for Port Engineering[S]. Beijing：China Construction Industry Press，2010.(in Chinese))
[21] 董志凌，曲月华，戴约林. 吹填软弱土夹层的真空预压加固方法探讨[J]. 水道港口，2015，36(4)：350–354.(DONG Zhilin，QU Yuehua，DAI Yuelin. Discussion on vacuum preloading reinforcement method for dredging interlayer soft soil[J]. Journal of Waterway and Harbor，2015，36(4)：350–354.(in Chinese))
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2024, Vol. 43 
