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Floods are natural processes that constitute a hazard to society when associated to improper land use. Anthropic activities in floodplains are a factor of vulnerability that converts a natural hazard into a threat factor, eventually leading to disaster. Nowadays, natural and social complex processes demand integrated assessments in order to improve their understanding, helping decision making over sustainable use of territory, as well as integrating society’s activity in ecosystems and potentials, restrictions and benefits that society obtain from them. In this context, the objective of this work was to build a composite vulnerability model for a floodplain under urban influence, using an integrated assessment approach. This model was based on three dimensions; threat, fragility and an ecosystem services provision. These dimensions were calculated using both primary and secondary information, and weights by specialists. Main results show that the area presents high vulnerability with an increasing gradient towards high and urbanized areas, associated with an important number and relevant ecosystem services. Also, a spatial heterogeneity of the three dimensions emerged, making evident this area’s complexity and the need of integrated assessments to approach it. The composite vulnerability model proposed presents an elevated potential for natural and social processes analysis in floodplains, which is crucial for these territory management. Moreover, these integrated dimensions could contribute to decision making in different levels, as well as generating important supplies for environmental management and land planning.
相似文献Gas well drilled through longwall mining abutment pillar could potentially face instability issue due to the strata deformation following longwall panel extraction. Therefore, it is imperative to adequately design the pillar size of a longwall mining in order to ensure the stability of the gas well penetrated longwall mining abutment pillar. In this paper, the determination of suitable pillar size for protecting gas well subjected to longwall mining operation was investigated. Two scenarios of longwall gateroad system including the three and four entry system with varying pillar sizes were assessed using numerical modelling approach. The results of this study indicate that the pillar geometry plays an important role on the vertical gas well stability. In addressing the suitable pillar size for the given case study considering three entry system, the suitable chain pillar and abutment pillar size were found to be 80 ft (24.4 m) wide by 120 ft (36.6 m) length and 104 ft (31.7 m) wide by 120 ft (36.6 m) length rib to rib, respectively. Whereas, if four entry system is used, the suitable chain pillar size is 48 ft (14.6) wide by 120 ft (36.6 m) length and the abutment pillar size is 104 ft (31.7 m) wide by 120 ft (36.6 m) length rib to rib. The proposed numerical modelling procedure presented in this paper can be a viable alternative and applied to other similar projects in order to determine an optimal pillar size for protecting gas well in longwall mining area.
相似文献This paper describes the main features related to lateral displacements with depth after successive lateral loading–unloading cycles applied to the top of reinforced-concrete flexible bored piles embedded in naturally bonded residual soil. The bored piles under study have a cylindrical shape, with 0.40-m in diameter and 8.0-m in length. Both bored piles types (P1 and P2) include an embedded steel pipe section in their center as longitudinal steel reinforcements: pile type P1 has another 16 steel rods as steel reinforcement to concrete while pile type P2 has no further steel reinforcement. Pile type P1 has three times as much stiffness (EI) and four and a half times the plastic moment (My) than pile type P2. A similar load–displacement performance was observed at initial loads as for small displacements of both piles. At this initial loading stage, the response of the reinforced concrete piles is a function of the soil characteristics and of a linear elastic pile deformation. During this stage, piles can even be understood as probes for evaluating soil reactions. For larger horizontal displacements, after the concrete section starts undergoing large deformations, approaching the ultimate bending moment, pile behavior and consequently the load–displacement relation starts to diverge for both piles. For pile P1 the values of relevant lateral displacements are extended to about 2.5-m in depth, while for pile P2 lateral displacements are mostly constrained to about 2.0-m in depth. Measurements of horizontal displacements of pile P1 against depth recorded with a slope indicator show that, after unloading, lateral loads at distinct stages (small and near failure loads), exhibits a much higher elastic phase of the system response. An analytical fitting model of soil reaction is proposed based on the measured displacements from slope indicator. The integration of a continuous model proposed for the soil reaction agrees fairly well with the measured displacements up to moments close to plastic limit. Results of load–displacement show that the stiffer pile (P1) was able to mobilize twice as much lateral load compared to pile P2 for a service limit displacement of about 20 mm. The paper shows results that enable the isolation of the structural variable through real scale pile load tests, thus granting understanding of its importance and enabling its quantitative visualization in examples of piles embedded in residual soil sites.
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