我国半干旱地区土壤的特性与可持续发展

我国年降水量250~ 450mm的半干旱地区,主要发育有栗钙土、淡黑垆土、黑麻土、黄绵土和灰钙土。前四者具有半干润土壤水分状况,后者存在干旱土壤水分状况。贫乏的土壤水分状况与区内的光热资源匹配不协调,限制了天然乔木林的正常生存,制约了农业的不稳定,但却适宜耐旱灌木和耐旱禾草植物生长。因此,区内可持续发展:一要发展水利,二要建造水平梯田,三要根据土壤适生耐旱草灌植物的特性,在发展农业的同时,扩大发展草业、饲养业、畜产品深加工业。     

古尔班通古特沙漠固定与半固定沙丘成因初探

处于干旱荒漠区的古尔班通古特沙漠因降水、冬季的积雪、悬湿砂层、丘间地和背风坡的植被、沙丘表层微弱的分化、砂物质粒度等因素的综合影响 ,以固定和半固定沙丘为主。由于沙丘的稳定性差 ,人类活动过程中应加强对它的保护。     

半干旱区涌流畦灌模型应用研究

涌流灌溉作为一种先进的节水灌溉方式,非常适用于水资源匮乏,经济基础薄弱的干旱和半干旱地区。通过对辽宁西部半干旱褐土区的涌流畦灌进行的试验研究,在应用ＹＳＭ畦灌分析模型的基础上,建立了简便易解的涌流畦灌模型并通过模型仿真对灌水质量进行评价,得到藻水技术要素的优化组合。     

半圆型防波堤的水力特性研究

采用不规则波浪试验,研究了半圆型防波堤的水力特性及堤上波力随各主要影响因素的变化规律。指出必须分别按出水堤或淹没堤计算堤上的波力,前者可用改进的合田公式;对于淹没堤,文中建议了计算波力的方法。     

Development of a tunable friction pendulum system for semi‐active control of building structures under earthquake ground motions

The Friction Pendulum System (FPS) isolator is commonly used as a base isolation system in buildings. In this paper, a new tunable FPS (TFPS) isolator is proposed and developed to act as a semi‐active control system by combining the traditional FPS and semi‐active control concept. Theoretical analysis and physical tests were carried out to investigate the behavior of the proposed TFPS isolator. The experimental and theoretical results were in good agreement, both suggesting that the friction force of the TFPS isolator can be tuned to achieve seismic isolation of the structure. A series of numerical simulations of a base‐isolated structure equipped with the proposed TFPS isolator and subjected to earthquake ground motions were also conducted. In the analyses, the linear quadratic regulator (LQR) method was adopted to control the friction force of the proposed TFPS, and the applicability and effectiveness of the TFPS in controlling the structure's seismic responses were investigated. The simulation results showed that the TFPS can reduce the displacement of the isolation layer without significantly increasing the floor acceleration and inter‐story displacement of the superstructure, confirming that the TFPS can effectively control a base‐isolated structure under earthquake ground motions.     

Influence of connection typology on seismic response of MR‐Frames with and without ‘set‐backs’

The work presented is aimed at the investigation of the influence of beam‐to‐column connections on the seismic response of MR‐Frames, with and without ‘set‐backs’, designed according to the Theory of Plastic Mechanism Control. The investigated connection typologies are four partial strength connections whose structural details have been designed to obtain the same flexural resistance. The first three joints are designed by means of hierarchy criteria based on the component approach and are characterized by different location of the weakest joint component, leading to different values of joint rotational stiffness and plastic rotation supply and affecting the shape of the hysteresis loops governing the dissipative capacity. The last typology is a beam‐to‐column connection equipped with friction pads devoted to the dissipation of the earthquake input energy, thus preventing the connection damage. An appropriate modelling is needed to accurately represent both strength and deformation characteristics, especially with reference to partial‐strength connections where the dissipation of the earthquake input energy occurs. To this aim, beam‐to‐column joints are modelled by means of rotational inelastic springs located at the ends of the beams whose moment‐rotation curve is characterized by a cyclic behaviour which accounts for stiffness and strength degradation and pinching phenomena. The parameters characterizing the cyclic hysteretic behaviour have been calibrated on the base of experimental results aiming to the best fitting. Successively, the prediction of the structural response of MR‐Frames, both regular frames and frames with set‐backs, equipped with such connections has been carried out by means of both push‐over and Incremental Dynamic Analyses. Copyright © 2016 John Wiley & Sons, Ltd.     

A comparison of groundwater recharge estimation methods in a semi‐arid,coastal avocado and citrus orchard (Ventura County,California)

We assess the relative merits of application of the most commonly used field methods (soil‐water balance (SWB), chloride mass balance (CMB) and soil moisture monitoring (NP)) to determine recharge rates in micro‐irrigated and non‐irrigated areas of a semi‐arid coastal orchard located in a relatively complex geological environment. Application of the CMB method to estimate recharge rates was difficult owing to the unusually high, variable soil‐water chloride concentrations. In addition, contrary to that expected, the chloride concentration distribution at depths below the root zone in the non‐irrigated soil profiles was greater than that in the irrigated profiles. The CMB method severely underestimated recharge rates in the non‐irrigated areas when compared with the other methods, although the CMB method estimated recharge rates for the irrigated areas, that were similar to those from the other methods, ranging from 42 to 141 mm/year. The SWB method, constructed for a 15‐year period, provided insight into the recharge process being driven by winter rains rather than summer irrigation and indicated an average rate of 75 mm/year and 164 mm/year for the 1984 – 98 and 1996 – 98 periods, respectively. Assuming similar soil‐water holding capacity, these recharge rates applied to both irrigated and non‐irrigated areas. Use of the long period of record was important because it encompassed both drought and heavy rainfall years. Successful application of the SWB method, however, required considerable additional field measurements of orchard ET_c, soil‐water holding capacity and estimation of rainfall interception – runoff losses. Continuous soil moisture monitoring (NP) was necessary to identify both daily and seasonal seepage processes to corroborate the other recharge estimates. Measured recharge rates during the 1996 – 1998 period in both the orchards and non‐irrigated site averaged 180 mm/year. The pattern of soil profile drying during the summer irrigation season, followed by progressive wetting during the winter rainy season was observed in both irrigated and non‐irrigated soil profiles, confirming that groundwater recharge was rainfall driven and that micro‐irrigation did not ‘predispose’ the soil profile to excess rainfall recharge. The ability to make this recharge assessment, however, depended on making multiple field measurements associated with all three methods, suggesting that any one should not be used alone. Copyright © 2000 John Wiley & Sons, Ltd.     

Spatial patterns and temporal stability of soil moisture across a range of scales in a semi‐arid environment

The antecedent soil moisture status of a catchment is an important factor in hydrological modelling. Traditional Hortonian infiltration models assume that the initial moisture content is constant across the whole catchment, despite the fact that even in small catchments antecedent soil moisture exhibits tremendous spatial heterogeneity. Spatial patterns of soil water distribution across three transects (two in a burnt area and one in an unburnt area) in a semi‐arid area were studied. At the transect scale, when the factors affecting soil moisture were limited to topographical position or local topography, spatial patterns showed time stability, but when other factors, such as vegetation, were taken into account, the spatial patterns became time unstable. At the point scale, and in the same areas, topographical position was the main factor controlling time stability. Scale dependence of time stability was studied and local topography and vegetation presence were observed to play an important role for the correlation between consecutive measures depending on the scale. Copyright © 2000 John Wiley & Sons, Ltd.     

克立格方法在个旧矿区芦塘坝10-9号矿体储量计算中的应用

在矿山生产实际中,准确估计矿体品位空间分布规律和总体储量有利于提高矿山生产效率,降低生产成本.文章采用对数克立格(Log Kriging)法和距离反比法以个旧锡矿芦塘坝10-9号矿体为研究对象计算储量,其结果分别与地质块段法计算的储量进行了对比,并探讨了前两种计算方法的影响因素及其产生误差的根本原因.