③ Data Analysis of Groundwater Distribution Conditions
(1) Stratigraphic distribution conditions
The typical site is located in the northern part of the North China Platform in terms
of the tectonic unit. It is the western part of the Beijing Depression and is overlaid
by Quaternary strata. The stratigraphic conditions are as follows:
(1) Quaternary: it is composed of loose alluvial-proluvial fluvial deposits, with the
thickness gradually increasing from 21.6 m in Suzhuang in the north to 55.2 m in
Jiaodao in the south. The lithology is dominated by cohesive soil and sandy cobble.
(2) Tertiary: the strata are located under Quaternary, with a lithology dominated by
conglomerate, sandstone and argillaceous shale.
(3) Cretaceous: it is located in the northwest of the site, namely the area to the west
of Liangxiang-Qianmen fault, with a thickness of 1000 m as exposed by the
Doudiandong drilling hole. The lithology is dominated by sandstone, conglomerate and shale, etc.
(4) Jixian System: it is distributed in the area to the east of Liangxiang-Qianmen
fault, 300–1000 m thick, with the lithology of siliceous dolomite and siliceous
dolomite limestone with shale interlayers.
(2) Hydrogeological conditions
① Groundwater distribution conditions
According to the engineering hydrogeological survey report of the disposal site,
there are mainly three groundwater layers within the Quaternary sedimentary
deposits with a buried depth of 49 m. The types of groundwater are perched water,
phreatic water–confined water and confined water from top to bottom. The 3D
model of the typical strata in the site area is shown in Fig. 5.67, and the typical
profile of strata and groundwater distribution at the site is shown in Fig. 5.68.
I. Perched water
It is distributed locally at the site and mainly occurs in the cohesive soil layer within
12 m depth below the surface. In the first third of July in 2005, its water level
elevation was measured to be 30.02–30.87 m, and the depth to water table was
8.90–10.00 m.
II. Phreatic water–confined water
It is widely distributed in the site area and occurs in the silt layer with a buried depth
of 13–15 m. The aquifer roof elevation is about 26.27–27.33 m, the floor elevation
is about 24.88–26.40 m and the thickness is about 0.4–1.5 m. In June 2015, its
water level elevation was measured to be 25.80–30.43 m, and the depth to water
table was 9.34–13.96 m.
Refer to Fig. 5.69 for the dynamic curve of inter-annual variations of the
groundwater level, we can be see that the groundwater level of this layer has shown
an overall tendency of decrease in the past three years, and there is no obvious law
of periodic dynamic changes within the year.
5.5 North China
297
(1) Stratigraphic distribution conditions
The typical site is located in the northern part of the North China Platform in terms
of the tectonic unit. It is the western part of the Beijing Depression and is overlaid
by Quaternary strata. The stratigraphic conditions are as follows:
(1) Quaternary: it is composed of loose alluvial-proluvial fluvial deposits, with the
thickness gradually increasing from 21.6 m in Suzhuang in the north to 55.2 m in
Jiaodao in the south. The lithology is dominated by cohesive soil and sandy cobble.
(2) Tertiary: the strata are located under Quaternary, with a lithology dominated by
conglomerate, sandstone and argillaceous shale.
(3) Cretaceous: it is located in the northwest of the site, namely the area to the west
of Liangxiang-Qianmen fault, with a thickness of 1000 m as exposed by the
Doudiandong drilling hole. The lithology is dominated by sandstone, conglomerate and shale, etc.
(4) Jixian System: it is distributed in the area to the east of Liangxiang-Qianmen
fault, 300–1000 m thick, with the lithology of siliceous dolomite and siliceous
dolomite limestone with shale interlayers.
(2) Hydrogeological conditions
① Groundwater distribution conditions
According to the engineering hydrogeological survey report of the disposal site,
there are mainly three groundwater layers within the Quaternary sedimentary
deposits with a buried depth of 49 m. The types of groundwater are perched water,
phreatic water–confined water and confined water from top to bottom. The 3D
model of the typical strata in the site area is shown in Fig. 5.67, and the typical
profile of strata and groundwater distribution at the site is shown in Fig. 5.68.
I. Perched water
It is distributed locally at the site and mainly occurs in the cohesive soil layer within
12 m depth below the surface. In the first third of July in 2005, its water level
elevation was measured to be 30.02–30.87 m, and the depth to water table was
8.90–10.00 m.
II. Phreatic water–confined water
It is widely distributed in the site area and occurs in the silt layer with a buried depth
of 13–15 m. The aquifer roof elevation is about 26.27–27.33 m, the floor elevation
is about 24.88–26.40 m and the thickness is about 0.4–1.5 m. In June 2015, its
water level elevation was measured to be 25.80–30.43 m, and the depth to water
table was 9.34–13.96 m.
Refer to Fig. 5.69 for the dynamic curve of inter-annual variations of the
groundwater level, we can be see that the groundwater level of this layer has shown
an overall tendency of decrease in the past three years, and there is no obvious law
of periodic dynamic changes within the year.
5.5 North China
297