Field scale determination of the aquifer–aquitard boundary in Joso Clay by cone penetrometry
Field scale determination of the aquifer–aquitard boundary in Joso Clay by cone penetrometry
复制标题
锥入度法现场尺度测定常总粘土含水层-弱透水层边界
DOI：
10.1111/j.1747-0765.2009.00377.x
复制
发表时间：
2009
期刊：
影响因子：
--
通讯作者：
M. Shiba
中科院分区：
文献类型：
--
作者：
S. Eguchi;M. Sawamoto;M. Shiba
摘要一些土壤剖面研究指出，日本茨城县南部和千叶县北部洪积高地浅层地下水体下的厚粘土层Joso Clay，其结构表面层的水力导电性比下伏块状层高一到几个数量级。构造层与块状粘土层边界的空间分布应确定为含水层-含水层边界；但是，并没有作出这样的尝试。在日本茨城县筑波-稻市高地，采用动态锥体穿透法在野外尺度上测定了佐佐黏土含水层-含水层边界的空间分布。在面积为943 m2的土地上，在54个矩形网格点上，以约5 m的间距，确定了动力锥突指数nd5，即单位深度的锥突入土所需锤击次数的每5 cm深度平均值，深度为3.1-3.7 m。野外尺度的nd5剖面资料表明，Joso粘土最上层广泛分布着nd5值达50 ~ 60 m−1的棱柱状构造。因此，提出了一个nd5 > 60 m−1的标准来确定该领域的潜在水量。确定到含水层-含水层边界的平均深度为2.58 m，范围为2.40 ~ 2.89 m。此外，各网格点的年水位监测显示，构造层厚度为0.30 ~ 0.75 m，占浅层年平均厚度0.40 ~ 0.87 m的61 ~ 100%。这些结果表明，在野外尺度上，佐索黏土最上层构造层是该高地浅层含水层的主要组成部分。
Abstract A few number of soil profile studies have pointed out that Joso Clay, a thick clayey layer underlying the shallow groundwater bodies in the diluvial uplands of southern Ibaraki and northern Chiba prefectures, Japan, has a structured surface layer in which the hydraulic conductivity is one to several orders of magnitude higher than that of the underlying massive layer. The spatial distribution of the boundary between the structured and massive clay layers should be determined as the aquifer–aquitard boundary; however, such attempts have not been made. In the present study, dynamic cone penetrometry was used to determine the spatial distribution of the aquifer–aquitard boundary in Joso Clay at a field scale in Tsukuba–Inashiki Upland, Ibaraki prefecture, Japan. The dynamic cone penetration index N d5, every 5-cm depth average of the number of hammer strikes required for the tip cone to enter into the soil per unit of depth, was determined to a depth of 3.1–3.7 m at 54 rectangular grid points with approximately 5-m spacing in a field with an area of 943 m2. The field-scale N d5 profile data suggested that prismatic structures with N d5 values of up to 50–60 m−1 are widely distributed in the uppermost layer of the Joso Clay. Accordingly, a criterion of N d5 > 60 m−1 was proposed for determining the underlying aquitard in this field. The depth to the aquifer–aquitard boundary was determined to be 2.58 m on average, ranging from 2.40 to 2.89 m. Furthermore, annual water table monitoring at each grid point showed that the thickness of the structured layer, varying from 0.30 to 0.75 m, occupied 61–100% of the annual average shallow aquifer thickness, which varied from 0.40 to 0.87 m. These results demonstrate the significance of the uppermost structured layer in the Joso Clay as the major part of the shallow aquifer at a field scale in this upland.
茨城县筑波高地斜坡湿地地下水硝酸盐还原带
DOI：
--
发表时间：
2004
期刊：
Jour.of Groundwater Hydrology 46(2)
影响因子：
--
作者：
Ioka;S.;Tase;N.
通讯作者：
N.
淤泥和粘土层对地下水中硝酸盐的作用-水力屏障或生化屏障。
DOI：
--
发表时间：
2004
期刊：
Jour.of Groundwater Hydrology 46(1)
影响因子：
--
作者：
Ioka;S.;Tase;N.
通讯作者：
N.