This paper proposes an approach to calculate the head difference at two sides of suspended waterproof curtains during multi-grade dewatering.The seepage during the dewatering process can be subdivided into three regio...This paper proposes an approach to calculate the head difference at two sides of suspended waterproof curtains during multi-grade dewatering.The seepage during the dewatering process can be subdivided into three regions:(i)seepage in pit,(ii)seepage between cur-tains,and(iii)seepage outside the pit.The flow rate of the first region is equal to the pumping rate,and the flow rate of the second and third regions can be obtained by numerical analysis.A numerical model is established to simulate the seepage in the second and third regions and its performance is validated by using the measured data of a series of field tests.The flow rate of each region is then used to derive formulae for the head difference in conventional dewatering,which can be used to determine the head difference at two sides of each waterproof curtain during multi-grade dewatering.The proposed formula expresses the head difference as a function of the relative depth of the curtain inserted into the confined aquifer,the thickness of the aquifer,the distance between two curtains,and the anisotropy of the hydraulic conductivity of the aquifer.The proposed numerical approach is further validated by using data derived from numerical analysis.The validation results demonstrated that the predictions of the proposed approach are acceptable and convenient.展开更多
为获得DR级高品位铁精矿产品、降低SiO_(2)与Al_(2)O_(3)的总含量,以非洲某高品位铁矿石为研究对象,开展磨矿—磁选工艺优化试验。结果表明,矿石TFe品位为65.92%,铁元素主要赋存于赤褐铁矿和磁铁矿中,为主要回收目标矿物。试样在一段磨...为获得DR级高品位铁精矿产品、降低SiO_(2)与Al_(2)O_(3)的总含量,以非洲某高品位铁矿石为研究对象,开展磨矿—磁选工艺优化试验。结果表明,矿石TFe品位为65.92%,铁元素主要赋存于赤褐铁矿和磁铁矿中,为主要回收目标矿物。试样在一段磨矿细度-0.074 mm占比为60%、一段弱磁和强磁场强分别为79.6 k A/m和398.0k A/m、强磁精矿精选场强为159.2 k A/m、强磁扫选场强为398.0 k A/m的条件下,可获得TFe品位68.11%、SiO_(2)+Al_(2)O_(3)含量1.20%、回收率82.96%的混磁精矿。产品分析显示,混磁精矿主要由赤褐铁矿和磁铁矿组成,原矿中的主要磁性铁矿物得到了有效富集。研究表明,采用磨矿—磁选工艺可实现该非洲铁矿中赤铁矿与磁铁矿的高效分选,尤其在控制精矿中铝、硅杂质含量方面优势显著,能够获得优质DR级铁精矿。展开更多
Where the Yellow River flows through the Haiyuan-Tongxin arc-form tectonic region on the northeastern side of the Qinghai-Xizang (Tibet) Plateau, as many as 10～21 basis and erosion terraces have been produced, among ...Where the Yellow River flows through the Haiyuan-Tongxin arc-form tectonic region on the northeastern side of the Qinghai-Xizang (Tibet) Plateau, as many as 10～21 basis and erosion terraces have been produced, among which the biggest altitude above river level is 401m and the formation age of the highest terrace is 1.57 Ma B.P. Based on comparative analysis of the Yellow River terraces located separately in the Mijiashan mountain, the Chemuxia gorge, the Heishanxia gorge and the other river terraces in the vast extent of the northern part of China, it has been found that the tectonic processes resulting in the formation of the terrace series is one of multi-gradational features, i.e., a terrace series can include the various terraces produced by tectonic uplifts of different scopes or scales and different ranks. The Yellow River terrace series in the study region can be divided into three grades. Among them, in the first grade there are 6 terraces which were formed separately at the same time in the vast extent of the northern part of China and represent the number and magnitude of uplift of the Qinghai-Xizang Plateau since 1.6 Ma B. P.; in the second grade there are 5 terraces which were separately and simultaneously developed within the Haiyuan-Tianjingshan tectonic region and represent the number and magnitude of uplift of this tectonic region itself since 1.6Ma B.P.; in the third grade there are 10 terraces which developed on the eastern slope of the Mijiashan mountain and represent the number and amplitude of uplift of the Haiyuan tectonic belt itself since 1.6Ma B.P. Comparison of the terrace ages with loess-paleosoil sequence has also showed that the first grade terraces reflecting the vast scope uplifts of the Qinghai-Xizang Plateau are very comparable with climatic changes and their formation ages all correspond to the interglacial epochs during which paleosoils were formed. This implies that the vast extent tectonic uplifts resulting in river down-cutting are closely related to the warm-humid climatic periods which can also result in river downward erosion after strong dry and cold climatic periods, and they have jointly formed the tectonic-climatic cycles. There exists no unanimous and specific relationship between the formation ages of the second and third grade terraces and climatic changes and it is shown that the formation of those terraces was most mainly controlled by tectonic uplifts of the Tianjingshan block and the Haiyuan belt. The river terraces in the study region, therefore, may belong to 2 kinds of formation cause. One is a tectonic-climatic cyclical terrace produced jointly by vast extent tectonic uplifts and climatic changes, and the terraces of this kind are extensively distributed and can be well compared with each other among regions. Another is a pulse-tectonic cyclical terrace produced by local tectonic uplifts as dominant elements, and their distribution is restricted within an active belt and can not be compared with among regions.展开更多
基金the National Natural Science Foundation for Surface Project of China(Grant Nos.51878157,41572273)the Jiangsu Natural Science Foundation,China(Grant No.BK20181282).
文摘This paper proposes an approach to calculate the head difference at two sides of suspended waterproof curtains during multi-grade dewatering.The seepage during the dewatering process can be subdivided into three regions:(i)seepage in pit,(ii)seepage between cur-tains,and(iii)seepage outside the pit.The flow rate of the first region is equal to the pumping rate,and the flow rate of the second and third regions can be obtained by numerical analysis.A numerical model is established to simulate the seepage in the second and third regions and its performance is validated by using the measured data of a series of field tests.The flow rate of each region is then used to derive formulae for the head difference in conventional dewatering,which can be used to determine the head difference at two sides of each waterproof curtain during multi-grade dewatering.The proposed formula expresses the head difference as a function of the relative depth of the curtain inserted into the confined aquifer,the thickness of the aquifer,the distance between two curtains,and the anisotropy of the hydraulic conductivity of the aquifer.The proposed numerical approach is further validated by using data derived from numerical analysis.The validation results demonstrated that the predictions of the proposed approach are acceptable and convenient.
文摘为获得DR级高品位铁精矿产品、降低SiO_(2)与Al_(2)O_(3)的总含量,以非洲某高品位铁矿石为研究对象,开展磨矿—磁选工艺优化试验。结果表明,矿石TFe品位为65.92%,铁元素主要赋存于赤褐铁矿和磁铁矿中,为主要回收目标矿物。试样在一段磨矿细度-0.074 mm占比为60%、一段弱磁和强磁场强分别为79.6 k A/m和398.0k A/m、强磁精矿精选场强为159.2 k A/m、强磁扫选场强为398.0 k A/m的条件下,可获得TFe品位68.11%、SiO_(2)+Al_(2)O_(3)含量1.20%、回收率82.96%的混磁精矿。产品分析显示,混磁精矿主要由赤褐铁矿和磁铁矿组成,原矿中的主要磁性铁矿物得到了有效富集。研究表明,采用磨矿—磁选工艺可实现该非洲铁矿中赤铁矿与磁铁矿的高效分选,尤其在控制精矿中铝、硅杂质含量方面优势显著,能够获得优质DR级铁精矿。
文摘Where the Yellow River flows through the Haiyuan-Tongxin arc-form tectonic region on the northeastern side of the Qinghai-Xizang (Tibet) Plateau, as many as 10～21 basis and erosion terraces have been produced, among which the biggest altitude above river level is 401m and the formation age of the highest terrace is 1.57 Ma B.P. Based on comparative analysis of the Yellow River terraces located separately in the Mijiashan mountain, the Chemuxia gorge, the Heishanxia gorge and the other river terraces in the vast extent of the northern part of China, it has been found that the tectonic processes resulting in the formation of the terrace series is one of multi-gradational features, i.e., a terrace series can include the various terraces produced by tectonic uplifts of different scopes or scales and different ranks. The Yellow River terrace series in the study region can be divided into three grades. Among them, in the first grade there are 6 terraces which were formed separately at the same time in the vast extent of the northern part of China and represent the number and magnitude of uplift of the Qinghai-Xizang Plateau since 1.6 Ma B. P.; in the second grade there are 5 terraces which were separately and simultaneously developed within the Haiyuan-Tianjingshan tectonic region and represent the number and magnitude of uplift of this tectonic region itself since 1.6Ma B.P.; in the third grade there are 10 terraces which developed on the eastern slope of the Mijiashan mountain and represent the number and amplitude of uplift of the Haiyuan tectonic belt itself since 1.6Ma B.P. Comparison of the terrace ages with loess-paleosoil sequence has also showed that the first grade terraces reflecting the vast scope uplifts of the Qinghai-Xizang Plateau are very comparable with climatic changes and their formation ages all correspond to the interglacial epochs during which paleosoils were formed. This implies that the vast extent tectonic uplifts resulting in river down-cutting are closely related to the warm-humid climatic periods which can also result in river downward erosion after strong dry and cold climatic periods, and they have jointly formed the tectonic-climatic cycles. There exists no unanimous and specific relationship between the formation ages of the second and third grade terraces and climatic changes and it is shown that the formation of those terraces was most mainly controlled by tectonic uplifts of the Tianjingshan block and the Haiyuan belt. The river terraces in the study region, therefore, may belong to 2 kinds of formation cause. One is a tectonic-climatic cyclical terrace produced jointly by vast extent tectonic uplifts and climatic changes, and the terraces of this kind are extensively distributed and can be well compared with each other among regions. Another is a pulse-tectonic cyclical terrace produced by local tectonic uplifts as dominant elements, and their distribution is restricted within an active belt and can not be compared with among regions.
