我国工程地质现状与发展方向

本文回顾了我国工程地质及其分支学科的发展和现状,指出了我国工程地质工作中存在的主要问题以及今后的发展趋向。     

Effect of snow and soil frost melting on the concentrations of suspended solids and phosphorus in two rural watersheds in Western Finland

Hydrological processes are known to have a considerable effect on nutrient transport from agricultural land to watercourses. In cold temperate regions peak discharges are caused not only by storm conditions but also by melting of snow and frost. The objective of this work was to investigate the effects of snow and frost melt on concentrations of phosphorus and suspended solids. The samples were taken using flowweighted automatic sampling techniques from two agricultural drainage basins. During the beginning of the snowmelt period the concentration of suspended solids was rather low by comparison with the total phosphorus concentration and the discharge. The different behaviour compared with the relationships found during storm conditions was probably caused by continuous extraction of the soil surface by low ionic concentration melt water, and to some extent by leaching from plant residues. The gradual decrease of total phosphorus concentration during the frost thawing period could be attributed to the gradually increasing proportion of the subsurface and ground water discharge in the runoff.     

Production of N2O,CH4, and CO2 from soils in the tropical savanna during the dry season

Emissions of N₂O, CH₄, and CO₂ from soils at two sites in the tropical savanna of central Venezuela were determined during the dry season in February 1987. Measured arithmetic mean fluxes of N₂O, CH₄, and CO₂ from undisturbed soil plots to the atmosphere were 2.5×10⁹, 4.3×10¹⁰, and 3.0×10¹³ molecules cm^-2 s^-1, respectively. These fluxes were not significantly affected by burning the grass layer. Emissions of N₂O increased fourfold after simulated rainfall, suggesting that production of N₂O in savanna soils during the rainy season may be an important source for atmospheric N₂O. The CH₄ flux measurements indicate that these savanna soils were not a sink, but a small source, for atmospheric methane. Fluxes of CO₂ from savanna soils increased ninefold two hours after simulated rainfall, and remained three times higher than normal after 16 hours. More research is needed to clarify the significance of savannas in the global cycles of N₂O, CH₄, CO₂, and other trace gases, especially during the rainy season.     

Origin of calcium in aerosols over the western North Pacific

Weekly aerosol samples were collected from March 1981 to June 1983 at the six stations in the western North Pacific region and analyzed for Ca and Na. By coupling data with those previously reported for Al (Tsunogai et al., 1985), the following results and conclusion have been obtained. There was a positive correlation between the atmospheric concentration of Al and the concentration of nonsea salt Ca (nssCa). The nssCa/Al ratios from the six stations, however, considerably varied (from 0.84±0.36 to 3.00±1.91), and the ratios were usally larger than those of the crustal average or of usual soil in Japan. The Ca/Al ratios of Asian desert soil and loess vary from 0.52 to 1.29, which are similar to the nssCa/Al ratios of aerosols in the surface air over the western North Pacific region except at Onna, Okinawa. The exception may be due to a local effect of coral. These results suggest that a large part of nonsea salt Ca in the surface air over the western North Pacific is derived from arid regions in Asia and that the nssCa/Al ratio in aerosol varies with that of the source material.     

冻土切削力学特性的试验和理论分析

利用笔者所研制的冻土切削试验台，在室内对不同冻土在不同温度、含水量、切削速度、切削深度和切刀前角下进行了一系列切削试验。结果表明，切削时，冻土主要呈脆性断裂破坏，其切削过程被认为是刀刃切入和撕裂冻土的结果，切削阻力随冻土温度降低而非线性增加，随切削速度提高而略有增加，随切削深度增加而近似线性增加，最佳切刀前角随切削深度增大有增大趋势。但平均切削阻力与最大切削阻力之比值对不同试验条件基本在０．４－０．６５间变化。同时，根据切削过程机理，从理论上建立了最大切削力模型，此模型考虑了切入和撕裂冻土阻力。     

华南湘赣粤地区红层残积红土的工程地质研究

通过对红层残积红土的粒度成分、矿物成分、化学成分、物理化学特性、宏观结构、微观结构特征的全面系统分析，揭示红层残积红土不仅经历了物理风化作用，而且经受过红土化作用，具有红土的一般特点，是一种强度稍高，压缩性中等，含较多游离氧化物的超固结土。最后对红层残积红土的工程地质评价提出建议，认为其特性与母岩有关，砂砾岩、砂岩残积红土接近花岗岩残积红土；粉砂岩、泥岩残积红土接近红粘土，并对地基承载力和变形等问题提出具体的评价意见。     

福建滨海木麻黄林下土壤性质的变化及其对林带更新的影响

研究了福建滨海沙地木麻黄防护林Ｍｏ的生物地球化学循环特征和林下土壤ｐＨ的变化，发现因Ｍｏ的生物地球化学循环不平衡引起的土壤微量元素Ｍｏ的耗竭和土壤的酸化是木麻黄林早衰和迹地更新生长不良的重要原因。提出了相应的对策建议。     

作物叶面蒸腾与棵间蒸发分摊系数的计算方法

依据在冬小麦和玉米冠层表面及冠层内部下方土壤表面的净辐射观测资料,建立了一个能较准确地反映叶面蒸腾与棵间土壤蒸发分摊系数物理变化规律的较实用的计算模式,结果表明,分摊系数(α)随叶面积指数(LAI)增加而增加,且具有明显的日变化,α在中午最小、早、晚稍大,这种日变化受叶气孔调节的影响。