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71.
Cost-effective network design for groundwater flow monitoring 总被引:1,自引:0,他引:1
The extensive use of groundwater resources has increased the need for developing cost-effective monitoring networks to provide an indication of the degree to which the subsurface environment has been affected by human activities. This study presents a cost-effective approach to the design of groundwater flow monitoring networks. The groundwater network design is formulated with two problem formats: maximizing the statistical monitoring power for specified budget constraint and minimizing monitoring cost for statistical power requirement. The statistical monitoring power constraint is introduced with an information reliability threshold value. A branch and bound technique is employed to select the optimal solution from a discrete set of possible network alternatives. The method is tested to the design of groundwater flow monitoring problem in the Pomona County, California. 相似文献
72.
具有悠久历史的石结构是砌体结构的重要组成部分,本文作者经广泛调研和试验分析:(1)提出以石粉为集料对石砌体进行抗震加固,寓环保与防灾于一体;(2)给出新型浆体配比和复合砂浆的强度等级,阐述加固技术和方法,建立灌浆石砌体抗震抗剪强度公式;(3)阐明抗震验算方法,提出基于模糊随机可靠理论的可靠性分析方法。 相似文献
73.
74.
RC框架结构薄弱层的层间位移可靠度水平考察 总被引:2,自引:0,他引:2
讨论了钢筋混凝土框架结构层间极限变形角的近似概率特性,考察了大震作用下20余幢钢筋混凝土框架结构薄弱层的层间位移可靠度水平,从而为直接基于位移可靠度的抗震设计中层间目标位移可靠度的确定提供了一定依据。 相似文献
75.
Mahdi Shadab Far Yuan Wang Yousif A. H. Dallo 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2019,13(1):82-98
Rock explosion has always been a complex problem because neither rock characteristics nor explosion waves could be accurately estimated. As such, this imposes a high uncertainty on deterministic methodologies available for damage prediction. In this paper, by defining two damage zones around the blast hole, including crushed and cracked zones, a first-order reliability analysis (FORM) was adopted to address this issue. For this purpose, FORM was used in a double-loop algorithm, where the inner loop was responsible for converging the FORM, and the outer loop was assigned to feed the inner loop with new cases. Using such nested-loop algorithm, the probability of exceedance was calculated for any desired damage zone radius. The maximum effect of the involved parameters on the failure probability induced around the blast hole was additionally studied using a parametric reliability analysis. The results showed that the radii for crushed and cracked zones are limited to 0.5 and 4.2?m, respectively, so that the probability of going beyond these limits is less than 1%. Moreover, the analyses of decoupled explosions showed that increasing the gap between the explosion charge and wall of the borehole could severely reduce the failure probability; however, the maximum effect of decoupling ratio occurs in the small range of radii between 0.3?mm and 2.35?m. 相似文献
76.
Time-dependent behaviour of the rock mass 总被引:1,自引:0,他引:1
E. Z. Lajtai 《Geotechnical and Geological Engineering》1991,9(2):109-124
Summary The strength of intact rock and the rock mass is time-dependent. For intact rock experimental verification is available, for the rock mass the scale of time-dependence is a matter of judgement. Rock mass classifications do however emphasize the effect of time on tunnel stability. This paper examines the source of time-dependence in rocks and the rock mass and suggests a technique for estimating the long term strength. The long term strength of the rock mass is controlled by the time-dependent weakening of intact rock. Frictional resistance, a major source of rock mass strength, increases rather than decreases with time. Lifetime estimation for rocks can be accomplished phenomenologically or mechanistically. The first is a statistical process of wide applicability, the second is more restrictive in usage as its applies only to materials that suffer time-dependent strain (creep). Although the mechanistic route is more appealing, it has a major drawback as it concentrates on steady state creep. There is no strong evidence for steady state creep in rocks. The technique for long term prediction is developed through the analysis of the failure rate under constant load. The failure rate for a given load and environment is established from the frequency distribution of time-to-failure data as measured in static fatigue tests. As expected, the failure rate is strongly affected by both the loading and the environmental condition. The influence, however, is systematic and predictable. 相似文献
77.
Abstract In many rural areas, reticulated water supply from large water resources schemes does not exist and many households obtain water from groundwater (GW), rainwater harvesting (RWH), run-of-river (ROR) flow, or combinations of these. While comprehensive yield–reliability analysis for large water resource systems is the norm, typical rural water supply analysis unrealistically aggregates data into monthly or annual time steps and does not incorporate reliability. A daily time-step simulation of household supply and frequency analysis of the number of days supplied in each year is used herein to: (a) demonstrate a realistic approach of yield–reliability analysis for RWH, ROR and combined RWH and ROR supply; and (b) show how combined utilization of the two can lead to improved supply. Integration of RWH and ROR supply has been found to improve yield and reliability substantially. The limitations of using the simpler mass curve analysis and the effect of applying a monthly time step are demonstrated. Citation Ndiritu, J., Odiyo, J. O., Makungo, R., Ntuli, C. & Mwaka, B. (2011) Yield–reliability analysis for rural domestic water supply from combined rainwater harvesting and run-of-river abstraction. Hydrol. Sci. J. 56(2), 238–248. 相似文献
78.
The design of spread footings on granular soils is generally governed by serviceability requirements. Recent studies have utilized databases of load tests to investigate the use of normalized load-settlement curves to model the behavior of footings on sands. A major limitation of available databases is that they are based primarily on data from plate load tests or footings that have an equivalent width smaller than 1.0 m. There is a need to confirm the applicability of these curves to footings of practical scale. The main objective of this paper is to update available normalized load-settlement curves using point measurements of settlement and load from full-scale footings. Bayesian techniques are employed in the updating process. Results indicate that the updated normalized load-settlement relationship is slightly more conservative but less uncertain than the current relationship. Results from an illustrative example involving serviceability limit state reliability analyses using footings with widths ranging from 1.5 to 3.0 m indicated that the updated relationship resulted in a slightly higher reliability level compared to the prior relationship. 相似文献
79.
Many state departments of transportation and consulting firms continue to use dynamic formulas because they are simple and inexpensive as compared to the preferred dynamic loading test with signal matching. Efforts to reduce the error and uncertainty associated with dynamic formulas are therefore warranted until dynamic monitoring becomes standard for every driven pile. However, dynamic formulas calibrated to national test pile databases have indicated inaccuracy and high uncertainty in the capacity prediction using dynamic formulas. A region-specific dynamic load test database was used to assess the accuracy and uncertainty in the Janbu, Danish and FHWA Gates formulas, recalibrate the equations for local conditions (construction practice, geology) and to generate resistance factors for use with Load and Resistance Factor Design (LRFD). Following recalibration, the capacity predictions became more accurate, and an observed dependence of the accuracy on the magnitude of resistance was eliminated for most driving conditions (e.g. end-of-driving, restrike). Previously reported static load test data were used to incorporate the transformation error associated with using the dynamic capacity to predict an equivalent static capacity. Resistance factors for use in Load and Resistance Factor Design (LRFD) were developed in consideration of American Association of State Highway and Transportation Officials–recommended load statistics and target reliability indices. Efficiency factors were used to assess the economic performance of each dynamic formula. Comparison of the accuracy and uncertainty of the recalibrated equations to a nationwide calibration illustrated the advantage of using a geologic-specific database for the calibration of resistance factors. 相似文献
80.