Displacement analytical prediction of shallow tunnel based on unified displacement function under slope boundary

For slope condition of ground surface, the asymmetrical deformation about the vertical center line and the horizontal center line of the tunnel cross section can be formed. A unified displacement function expressed by the Fourier series is presented to express the asymmetrical deformation of the tunnel cross section. Five basic deformation modes corresponding to the expansion order 2 are a complete deformation mode to reflect deformation behaviors of the tunnel cross section under slope boundary. Such this complete displacement mode is implemented into the complex variable solution for analytically predicting tunneling-induced ground deformation under slope boundary. All of these analytical solutions are verified by good agreements of the comparison between the analytical solutions and finite element method results. A parameter study is carried out to investigate the influence of deformation modes of the tunnel cross section, geometrical conditions of the tunnel and the slope angle, and “Buoyancy effect” on the displacement field. Finally, the proposed method is consistent with measured data of the Hejie tunnel in China qualitatively. The presented solution can provide a simplified indication for evaluating the ground deformation under slope condition of ground surface.     

Efficient DEM‐based overland flow routing using integrated recursive algorithms

Two primary concerns in performing watershed overland flow routing are the numerical instability and computational efficiency. The stability of executing an explicit scheme has to be maintained by observing the Courant–Friedrich–Lewy criterion, which is adopted to confirm that the numerical marching speed is larger than the wave celerity. Moreover, there is another criterion of time step devised in previous studies to avoid back‐and‐forth refluxing between adjacent grids. The situation of refluxing usually occurs on flat regions. In light of this, the selection of a small time increment to honor both restrictions simultaneously is believed to decrease the computational efficiency in performing overland flow routing. This study aims at creating a robust algorithm to relax both restrictions. The proposed algorithm was first implemented on a one‐dimensional overland plane to evaluate the accuracy of the numerical result by comparing it with an analytical solution. Then, the algorithm was further applied to a watershed for 2D runoff simulations. The results show that the proposed integrated algorithm can provide an accurate runoff simulation and achieve satisfactory performance in terms of computational speed.     

Revised runoff curve number for runoff prediction in the Loess Plateau of China

The soil conservation service (now Natural Resources Conservation Service) Curve Number (SCS-CN), one of the most commonly used methods for surface runoff prediction. The runoff calculated by this method was very sensitive to CN values. In this study, CN values were calculated by both arithmetic mean (CN_C) and least square fit method (CN_F) using observed rainfall-runoff data from 43 sites in the Loess Plateau region, which are considerably different from the CN₂ values obtained from the USDA-SCS handbook table (CN_T). The results showed that using CN_C instead of CN_T for each watershed produce little improvement, while replacing CN_T with CN_F improves the performance of the original SCS-CN method, but still performs poorly in most study sites. This is mainly due to the SCS-CN method using a constant CN value and discounting of the temporal variation in rainfall-runoff process. Therefore, three factors—soil moisture, rainfall depth and intensity—affecting the surface runoff variability are considered to reflect the variation of CN in each watershed, and a new CN value was developed. The reliability of the proposed method was tested with data from 38 watersheds, and then applied to the remaining five typical watersheds using the optimized parameters. The results indicated that the proposed method, which boosted the model efficiencies to 81.83% and 74.23% during calibration and validation cases, respectively, performed better than the original SCS-CN and the Shi and Wang (2020b) method, a modified SCS-CN method based on tabulated CN value. Thus, the proposed method incorporating the influence of the temporal variability of soil moisture, rainfall depth, and intensity factors suggests an accurate runoff prediction for general applications under different hydrological and climatic conditions on the Loess Plateau region.     

甘肃省第一次全国地理国情普查数据库设计

地理国情普查数据库是地理国情普查成果数据存储、管理和分发应用的基础,为地理国情动态监测提供本底数据库。本文从甘肃省实际情况出发,结合信息化测绘服务体系和"天地图·甘肃"等现有成果,从数据库概念设计、逻辑设计、物理设计、接口设计,以及数据库管理系统和地理国情展示系统等方面进行了详细的设计,为全面开展地理国情普查数据库建设奠定了坚实的基础。     

齐齐哈尔市地理国情分析与表达

以齐齐哈尔市为例,利用地理国情普查数据与统计年鉴数据,构建自然地表指数、地理区位指数、生态覆被指数,对齐齐哈尔市各县、区的地理国情进行综合分析和地图表达。结果表明,齐齐哈尔市的总体条件较好,但区域差异较大,自然地表条件与地理区位条件均以中部的齐齐哈尔市辖区为优,而生态覆被条件则以北部和西部地区为优。     

地理国情普查外业调绘核查系统实现

针对传统的基于纸质地图的外业调绘核查工作具有操作复杂、采集数据不精确、作业流程不规范等缺点,该文设计开发了基于iPad的地理国情普查外业调绘核查系统。在内业高精度遥感影像判读的基础上,采用全数字化的外业调绘核查技术,进行地理国情要素移动式、网络化外业调查和验证,快速采集和编辑调查数据,为外业工作提供了一套完整的解决方案。该系统在青岛市崂山区和城阳区的试点中已经得到广泛的应用,较好地验证了移动GIS技术用于外业信息采集的可行性。     

Deciphering As and Cu cycling in sediment pore waters in a large marina (Port Camargue,southern France) using a multi-tracer (Fe,Mn, U,Mo) approach

The sediments of the Port Camargue marina (South of France) are highly polluted by Cu and As (Briant et al., 2013). The dynamics of these pollutants in pore waters was investigated using redox tracers (sulfides, Fe, Mn, U, Mo) to better constrain the redox conditions.In summer, pore water profiles showed a steep redox gradient in the top 24 cm with the reduction of Fe and Mn oxy-hydroxides at the sediment water interface (SWI) and of sulfate immediately below. Below a depth of 24 cm, the Fe, Mn, Mo and U profiles in pore waters reflected Fe and Mn reducing conditions and, unlike in the overlying levels, sulfidic conditions were not observed. This unusual redox zonation was attributed to the occurrence of two distinct sediment layers: an upper layer comprising muddy organic-rich sediments underlain by a layer of relatively sandy and organic-poor sediments. The sandy sediments were in place before the building of the marina, whereas the muddy layer was deposited later. In the muddy layer, large quantities of Fe and Mo were removed in summer linked to the formation of insoluble sulfide phases. Mn, which can adsorb on Fe-sulfides or precipitate with carbonates, was also removed from pore waters. Uranium was removed probably through reduction and adsorption onto particles. In winter, in the absence of detectable pore water sulfides, removal of Mo was moderate compared to summer.Cu was released into solution at the sediment water interface but was efficiently trapped by the muddy layer, probably by precipitation with sulfides. Due to efficient trapping, today the Cu sediment profile reflects the increase in its use as a biocide in antifouling paints over the last 40 years.In the sandy layer, Fe, Mn, Mo and As were released into solution and diffused toward the top of the profile. They precipitated at the boundary between the muddy and sandy layers. This precipitation accounts for the high (75 μg g⁻¹) As concentrations measured in the sediments at a depth of 24 cm.     

贵州桐梓新桥浑水河的成因再探讨

通过对新桥浑水河上游明流段、中部伏流段、下游浑水河段实地调查,并结合该区1:20万区域地质资料、区域水文地质资料及煤矿勘查资料,在分析浑水河区域构造背景及水文地质特征的基础上,研究了浑水河的水动力条件,包括纵向水动力条件和横向水动力条件,认为浑水河是特殊构造通道、水土流失带来的粘土颗粒物源、携带粘土颗粒的水体进入地下伏流,粘土颗粒在河床中沉积后又被流水带出的一个过程,即"流失→带进→沉积→带出"过程。浑水河的成因:1浑水河的特殊构造,具备了通道条件;2上游水土流失带来的大量细小粘土颗粒提供了物源;3洞湾水体"盲谷"是浑水的物源载体;4地下伏流的水动力条件,包括纵向水动力条件和横向水动力条件,四者共同作用的结果。     

晋中至太原城际铁路沿线地质条件分析

晋中至太原城际铁路位于山西断陷带次级构造单元太原断陷盆地内,盆地内部新构造运动复杂,城际铁路沿线跨越多条第四纪隐伏活动断裂,并穿过榆次地裂缝发育地带及砂土液化区域,这些地质问题极大地影响着晋中至太原城际铁路的前期勘测选线。本文从地质构造、地层岩性、浅层地震勘探等方面对穿越城际铁路的三条活动断裂的危险性进行了分析评价,以查明断裂错动对城际铁路的影响。结合前人对榆次地裂缝的研究成果,对城际铁路附近的地裂缝发育情况进行了调查验证,以查明榆次地裂缝对城际铁路的影响。通过在城际铁路车站及车辆段布置地质钻孔,进行标贯试验、剪切波速测试,以查明城际铁路沿线工程地质条件,对沿线车站及车辆段场地进行液化判定及场地类别判定。针对城际铁路沿线存在的上述地质问题,给出了相应的工程建议,对城际铁路前期勘测设计具有重要的指导意义。     

Paleo-redox depositional conditions inferred from trace metal accumulation in two Cretaceous-Paleocene organic-rich sequences from Central Egypt

Cretaceous-Paleocene organic-rich sediments in Egypt occur as an east-west trending belt extending from the Quseir-Safaga district (Red Sea) to the Kharga-Dakhla (Western Desert) region. They are associated with the Duwi Formation (phosphate-bearing) and the overlying Dakhla Formation (deeper epicontinental shale/marl). This study aims to reconstruct the paleo-redox conditions during deposition of these thermally immature organic-rich sediments using carbon-sulfur-iron systematics and trace metal proxies in two cores, one each from the Quseir and Abu Tartur areas. Paleoproductivity, based on P content, seems to have been higher in the Quseir section than in the Abu Tartur section. The Quseir section also records a relatively greater occurrence of anoxic conditions during the accumulation of these sediments than the Abu Tartur section. This difference is indicated by its markedly higher total organic carbon (TOC) content as well as higher contributions of redox-sensitive and sulfide-forming metals (Mo, U, Ni, V, and Co). A weak correlation exists between S and TOC, and a positive S intercept (>1) was observed in most of the rock units of the study sections. A high consistency between the TOC-S-Fe relations and trace metals findings was found. The uppermost Duwi and the lowermost Dakhla strata, which have the highest TOC and represent a maximum sea transgression during the Late Cretaceous, have the highest contents of redox-sensitive trace metals. The carbonate-dominated transgressive Baris and Beida members of the Dakhla Formation record relatively stronger oxygen-depleted conditions during their accumulation than others, which led to relatively higher TOC contents and redox-sensitive metal accumulations. A scenario for the environmental conditions that existed during the deposition of these organic-rich successions, based on compiled trace metals and TOC-S-Fe implications, is reconstructed here.