摘要
钙华是一种大孔隙次生碳酸钙,是岩溶水在适宜的环境下碳酸钙过饱和沉积而形成,不同成因的钙华形成了绚丽多彩的自然景观。钙华沉积速率快,对气候和环境极具敏感性,近年来被广泛用于短时间尺度的古气候环境重建研究。由于钙华主要分布于水流活动频繁的偏远地区,较少用于工程建设,故国内外对其工程性质少有研究。本文以南美洲玻利维亚东南地区某冶金项目为依托,实地研究了湖沼相钙华的工程性质,通过渗水试验测试了钙华层的渗透系数,通过浸水载荷试验,研究了钙华的承载力特性和溶陷性。结果表明:钙华的渗透系数为1.7×10^-3 cm·s^-1;变形模量为45.39 MPa,在浸水之后变形模量有所降低,但仍然可达到36.85MPa;浸水状态下地基承载力特征值高于280kPa,浸水3h后的浸润深度为0.65m;钙华的平均溶陷系数为0.00175,为非溶陷性岩石。通过试验可以得出如下结论:(1)钙华遇水后的稳定性较差,基坑和基础施工宜安排在旱季。(2)钙华在天然状态下的承载力较高,遇水后承载力会有所降低,应尽可能保持基底干燥。③钙华的渗透系数较小,短时间的水流对钙华层的浸润深度较小,雨季来临时,只要做好地基的覆盖,就可以使地基保持较高的承载力。
Travertine is a kind of macroporous secondary calcium carbonate,formed by Karst water.Travertine can create beautiful natural landscapes such as the Huanglong scenic spot in China,the Pamukkale in Turkey,and the Yellowstone Park Mammoth Hot Springs in the United States.While travertine is mainly distributed in the carbonate areas with frequent water flow,it is rarely used as foundation of buildings and its engineering characteristics are less studied.The project location is in Bolivia,South America,where a steel plant is to be built upon a Travertine land.The travertine in this area is formed by the lacustrine facies,grayish-white,visible honeycomb-like or spongy voids,with some of the voids filled with clay.The SPT N value of the travertine is 39 to 77,which has good mechanical properties in the natural state.But when the travertine is submerged in water,it collapses quickly.Rain in Bolivia lasts for four months annually,it is worried that rain can damage the travertine foundation.A study is thus conducted to test the properties of travertine in the construction site.It is found that the permeability of travertine is 1.7×10^-3 cm·s^-1.The load test is divided into two groups,P1 and P2.The P1 test point is used to test the bearing capacity and collapsibility under the condition of immersion.P1 is soaked in water before the test,and the water head height was 30cm for 5 days.The P2 test site is used to test the elastic modulus of the natural state and evaluate the collapsibility.In both tests,the first load is kept to 200kPa and then the test pit is injected water evenly,with a constant head height of 30cm.The results show that the deformation modulus of the travertine can reach 45.39MPa in natural state and 36.85MPa in immersion state;that the foundation bearing capacity is more than 280kPa in immersion state;and that the depth of infiltration is 0.65m after 3 hours of immersion.It is concluded that the stability of the travertine in water is poor and the construction in the dry season is recommended.The bearing
作者
孟庆洲
王殿斌
孙玺
汪名友
MENG Qingzhou;WANG Dianbin;SUN Xi;WANG Mingyou(Qingdao Research Center for Geotechnical Engineering,Qingdao 266000,China;Qingdao Geotechnical&Foundation Engineering Co.,Qingdao 266000,China;Qingdao Surveying&Mapping Institute,Qingdao 266000,China)
出处
《工程地质学报》
CSCD
北大核心
2020年第6期1172-1177,共6页
Journal of Engineering Geology
关键词
钙华
渗透系数
承载力
溶陷性
Travertine
Coefficient of permeability
Bearing capacity
Collapsible
