Natural Hazards - Failure angle, also called maximum safe slope angle, is an important design parameter for rock slope stability analysis and slope excavation. This study aims to scientifically... 相似文献
The possibility of using concrete as a construction material at the Moon surface is considered. Dissimilarities between the Earth and the Moon and their possible effects on concrete are also emphasized. Availability of constituent materials for concrete at lunar surface is addressed. An emphasis is given to two types of materials, namely, hydraulic concrete and sulfur concrete. Hydraulic concrete necessitates the use of water and sulfur concrete makes use of molten sulfur in lieu of cement and water. 相似文献
Climate Dynamics - We employ a Lagrangian based moisture back trajectory method on an ensemble of four reanalysis datasets to provide a comprehensive understanding of moisture sources over the... 相似文献
To increase soil productivity, ameliorate nutrient scarcity, and reduce metal toxicity in highly weathered acidic soils usually requires fertilizer and lime application. Effects of three biochars on soil acidity, Olsen-phosphorus (P), phosphatase activities, and heavy metal availability were investigated to test potential of these biochars as soil amendments in highly weathered acidic soils. Incubation experiments were conducted for 6 weeks with three acidic soils: Alfisol, Ultisol, and Oxisol. Three biochars were derived from chicken manure (CMB), pig manure (PMB), and peat moss (PB) at 400 °C and applied at 1 or 2% (wt/wt). The addition of the three biochars increased Olsen-P in the three acidic soils in the following order: CMB?>?PMB?>?PB. Application of 2% CMB increased Olsen-P contents by 2.41-, 7.4-, and 1.78-fold in the Ultisol, Oxisol, and Alfisol compared with controls, respectively. Moreover, CMB increased the soil pH, electrical conductivity (EC), cation exchange capacity (CEC), and alkaline phosphatase activity, but reduced exchangeable acidity, acid phosphatase activity, and the availability of heavy metals—more effectively than PMB and PB. Addition of CMB increased soil pH by 0.90, 0.90, and 0.92 units for the Alfisol, Ultisol, and Oxisol, respectively, correspondingly followed by 0.80, 0.84, and 0.87 units for PMB and 0.15, 0.28, and 0.25 for PM. Changes in EC, CEC, and exchangeable acidity followed the same order for the three soils: CMB?>?PMB?>?PB. The results suggested that the magnitude of changes in soil properties and Olsen-P contents depended on biochar type and application rate. Application of CMB increased nutrient availability and reduced the availability of heavy metals more than other amendments. Due to higher pH, EC, and CEC, and greater concentrations of carbon, nitrogen, and exchangeable calcium and potassium, incorporation of CMB should be a better cost-effective method to correct soil acidity and improve fertility and Olsen-P contents in Ultisols and Oxisols from tropical and subtropical regions of the world. 相似文献
The Nagar Parkar Igneous Complex consists of Neoproterozoic igneous and metamorphic rocks dissected by mafic, felsic, and rhyolitic dykes. The latter can be classified broadly into porphyritic felsic dykes intruding gray and pink granites at Nagar Parkar and the surrounding areas, and the orthophyric felsic dykes intruding amphibolites, deformed pink granites, and the alkaline mafic dykes in the Dhedvero area, north of Nagar Parkar. The porphyritic felsic dykes are composed of perthites, quartz, and albitic plagioclase whereas the orthopheric felsic dykes contain K-feldspar (dominant), plagioclase, and minor quartz. Geochemically, the porphyritic and orthophyric felsic dykes are subalkaline and alkaline demonstrating post-orogenic A2- and OIB-A1-type characteristic on Nb–Y–Ce and Nb–Y–3Ga ternary plots, respectively. One orthophyric felsic dyke contains normative acmite and sodium metasilicate. This study suggests two distinct tectonic regimes for the origin of the felsic dykes of the area. The porphyritic felsic dykes show similarities with the ~800–700 Ma granites of the area, the rhyolite dykes of the Mount Abu, western Rajasthan in India, and the granites of the Seychelles microcontinent. The orthophyric felsic dykes show chemical resemblance with the Tavidar volcanic suite of western Rajasthan and the Silhouette and North islands of the Seychelles microcontinent. This study confirms spatial and temporal links among the Rodinian fragments exposed in the Nagar Parkar area of Pakistan, western Rajasthan of India, and the Seychelles microcontinent. 相似文献
The vegetation of the wasteland of Valika chemical industries near Manghopir road, Karachi was studied. Nine plant communities were recognized based on dominant species. In these plant communities the vegetation was disturbed, mostly halophytic and dominated bySuaeda fruticosa,Tamarix indica,Salsola baryosma,Cressa cretica,Atriplex griffithii,Haloxylon recurvum,Indigofera hochstetteri,Prosopis julifloraandChenopodium album.The physico-chemical properties of the soils were also analysed. Soil texture was mostly sandy loam, which exhibited slight variations in the water-holding capacity. The soils contained a sufficient amount of CaCO3−and exhibited mostly alkaline soil pH. The soils of the different plant communities had scarcely any organic matter or inorganic phosphorus. The exchangeable sodium in the soils of many halophytic plant communities was high, with appreciable concentrations of potassium. 相似文献
Although hydraulic fracturing has been massively studied and applied as a key technique to enhance the gas production from tight formations, some problems and uncertainties exist to accurately predict and analyze the fracture behavior in complex reservoirs, especially in the naturally fractured reservoirs like shale reservoirs. This paper presents a full 3D numerical model (FLAC3D) to study hydraulic fracturing behavior under the impact of preexisting orthogonal natural fractures. In this numerical model, the hydraulic fracture propagation direction is assumed perpendicular to the minimum principal stress and activated only by tensile failure, whereas the preexisting natural fractures can be activated by tensile or shear failure or a combination of them, and only tensile failure can open the natural fracture as well. The newly developed model was used to study the impact of preexisting orthogonal natural fractures on hydraulic fracturing behavior, based on a multistage hydraulic fracturing operation in a naturally fractured reservoir from the Barnett Shale formation, northwest of Texas in USA. In this multistage operation, two more representative stages, i.e., stage 1 with a relatively large horizontal stress anisotropy of 3.3 MPa and stage 4 with a comparatively small one of 1.3 MPa, were selected to conduct the simulation. Based on the numerical results, one can observe that the interaction between hydraulic and natural fracture is driven mainly by induced stress around fracture tip. Besides, the horizontal stress anisotropy plays a key role in opening the natural fracture. Thus, no significant opened fracture is activated on natural fracture in stage 1, while in stage 4 an opened fracture invades to about 90 m into the first natural fracture. Conversely, the hydraulic fracture length in stage 1 is much longer than in stage 4, as some fluid volume is stored in the opened natural fracture in stage 4. In this work, the shear failure on natural fractures is treated as the main factor for inducing the seismic events. And the simulated seismic events, i.e., shear failure on natural fractures, are very comparable with the measured seismic events.
A large number of paleo-landslide deposits exist in the Southeastern margin of the Qinghai–Tibet Plateau. Once these deposits are destroyed, the disaster chain will cause huge damage to life and property and have an impact on local geomorphic evolution. Diverse models are applied to analyze different geological problems of paleo-landslide deposits, which can produce the advantages of different models fully, thereby making up for the shortcomings of poor applicability of a single model in a certain type of problem. In this study, the Baimu paleo-landslide deposit located at the North side of Dongjiuqu Bridge of Sichuan-Tibet Railway is taken as the research object to completely analyze the potential damage by combining various technical means and numerical model, aiming to provide certain reference for the design and construction of the project. Firstly, site investigation and terrain interpretation confirm the existence of local deformation and damage. Secondly, the finite element model based on the strength reduction method is used to analyze the stability of the deposit and determine the potential damage area. For the potential damage area, debris avalanche and debris flow as two disaster transformation modes are considered. The discrete element model and shallow flow model are used to simulate the dynamic process of debris avalanche and debris flow under complex terrain, respectively. The results show that potential debris avalanche or debris flow will accumulate at the mouth of the Baimu gully, and there will be no direct threat to the bridge. Finally, the formation and evolution sequence of the deposit is proposed, which plays an important role in analyzing the evolution of local river geomorphology.
Geoelectric and hydrochemical approaches are employed to delineate the ground-water potential zones in District Okara, a part of Bari Doab, Punjab, Pakistan. Sixty-seven VES surveys are conducted with the Electrical Resistivity Meter. The resultant resistivity verses depth model for each site is estimated using computer-based software IX1D. Aquifer thickness maps and interpreted resistivity maps were generated from interpreted VES results. Dar-Zarrouk parameters, transverse resistance (TR), longitudinal conductance (SL) and anisotropy (λ) were also calculated from resistivity data to delineate the potential zones of aquifer. 70% of SL value is ≤3S, 30% of SL value is > 3S. According to SL and TR values, the whole area is divided into three potential zones, high, medium and low potential zones. The spatial distribution maps show that north, south and central parts of study area are marked as good potential aquifer zones. Longitudinal conductance values are further utilized to determine aquifer protective capacity of area. The whole area is characterized by moderate to good and up to some extent very good aquifer protective area on the basis of SL values. The groundwater samples from sixty-seven installed tube wells are collected for hydro-chemical analysis. The electrical conductivity values are determined. Correlation is then developed between the EC (μS/cm) of groundwater samples vs. interpreted aquifer resistivity showing R2 value 0.90. 相似文献
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