上细下粗富水复合砂层渗透破坏机制试验及初步工程应用研究  

Experimental study on seepage failure mechanism in an upper-fine-lower-coarse composite sandy strata and its preliminary engineering application

作　　者：潘泓[1,2] 蔡磊 罗俊兴 曹洪[1,2] 骆冠勇[1,2] PAN Hong;CAI Lei;LUO Junxing;CAO Hong;LUO Guanyong(School of Civil Engineering and Transportation,South China University of Technology,Guangzhou,Guangdong 510640,China;The State Key Laboratory of Subtropical Building Science,South China University of Technology,Guangzhou,Guangdong 510640,China;CCCC Fourth Harbor Engineering Institute Co.,Ltd.,Guangzhou,Guangdong 510230,China)

机构地区：[1]华南理工大学土木与交通学院,广东广州510640 [2]华南理工大学亚热带建筑科学国家重点实验室,广东广州510640 [3]中交四航工程研究院有限公司,广东广州510230

出　　处：《岩石力学与工程学报》2023年第7期1778-1788,共11页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(51978282);广东省自然科学基金资助项目(2023A1515011571);华南理工大学亚热带建筑科学国家重点实验室开放研究项目(2022ZB21)。

摘　　要：高富水砂层易发生渗透破坏,是地下工程施工主要风险源。目前对“上细下粗”复合砂层的渗透破坏致灾机制的尚不清楚。通过分析对比14组砂土侵蚀模型试验数据,发现由下层粗砂、上层细砂组成的“上细下粗”的复合砂层渗流破坏特征与单一砂层显著不同,其渗透破坏的机制为:下层粗砂的渗透性显著大于上层粉细砂层,两者形成串联关系,下层强透水层能耗小,主要起供水作用,上层细砂层有一定厚度且渗透性小,承受大部分的渗透压力,从而使细砂颗粒迅速流失,导致流土型渗透破坏。在相同边界条件下,地下水对复合砂层土体扰动范围更广,土体流失更显著,流失速率更快。当渗漏出口接近粗砂与细砂交界面且处于细砂一侧时,流土现象最为显著。基于试验得到的规律,对2018年佛山“2.7”地铁事故发生大面积坍塌的原因进行探讨,认为“上细下粗”复合砂层及渗漏出口独特位置——“粉砂和中粗砂交界处”是造成该事故大面积坍塌的重要地层条件。在类似工程需重视复合砂层的识别,并做好密封措施,防止渗漏出口的出现。Highly water-rich sand strata is prone to causing seepage failure and is the main risk source for underground construction.At present,the mechanism of seepage failure in the composite strata of“upper fine and lower coarse”is not clear.By analyzing and comparing 14 groups of sand erosion model test data,it is found that the seepage damage characteristics of the composite strata composed of the lower coarse sand and the upper fine sand are significantly different from that of the single strata.The lower layer has small energy consumption and mainly plays the role of water supply,while the upper layer of fine sand has small permeability and bears most of the seepage force,thus causing rapid loss of fine sand particles and leading to sand boiling/static liquefaction.Under the same boundary conditions,groundwater disturbs the soil of the composite strata more extensively,and the soil loss is more significant and the loss rate is faster.The sand boiling phenomenon is most significant when the seepage outlet is close to the interface of coarse sand and fine sand and on the side of fine sand.Based on the observations obtained from the test,the causes of the large area collapse in the“2.7”subway accident in Foshan in 2018 were discussed.It is considered that the composite sand layer of“fine top and coarse bottom"and the unique location of the leakage outlet-"the interface of fine sand and medium coarse sand”are the main causes of the large area collapse of the accident.In similar projects,it is necessary to pay attention to the identification of the composite sand layer and make good sealing measures to prevent the emergence of the seepage outlet.

关 键 词：土力学 复合砂层 流土 渗流破坏 盾构 

分 类 号：TU44[建筑科学—岩土工程]