宁夏不同土壤类型日光温室土壤理化性质的变化特点

根据宁夏温室的分布状况,按照土壤类型(灌淤土、黑垆土、灰钙土)分别采集了不同层次温室土壤,分析了土壤理化性质的变化特点。结果表明,灰钙土、灌淤土的容重较大,而黑垆土的容重较小;土壤孔隙度、有机质、全氮、硝态氮、全磷、速效磷、速效钾、缓效钾均表现为黑垆土>灌淤土>灰钙土;全盐量的高低依次为灌淤土>灰钙土>黑垆土;黑垆土、灰钙土的pH值较高,而灌淤土较低;碱解氮的高低依次为灌淤土、黑垆土>灰钙土。多重比较结果表明,土壤全盐、pH值、有机质、全磷、缓效钾在3类土壤间差异显著。

土性和埋深对增阻推力的影响研究

针对土性和埋深对增阻推力的影响,采用模型试验方法进行了研究,利用正交试验法进行了模型试验,得到筒体在不同土体中由增阻力提供推力与所研究参数的关系,从而指导自行走掘进机的设计和施工。

克什克腾旗耕地土壤氮元素现状分析

本文对克什克腾旗(以下简称克旗)的耕地土壤全氮和碱解氮含量进行了野外调查与室内实验分析,结果如下:1克旗耕地土壤中的全氮含量处于中等以上水平,各土类中,黑土含量和灰色森林土的含量显著偏多.2克旗耕地土壤中的碱解氮处于偏低水平,大多少于150 mg/kg.各土类中,黑土的含量最高.

干湿循环作用下土体的三轴剪切特性研究现状

土体的剪切特性是土体受到剪切破坏时表现出来的宏微观特性。宏观上表现为抗剪强度以及黏聚力和内摩擦角的变化,微观上表现为微结构的变化,而干湿循环作用显著改变了土体的剪切特性。研究过程中,以干湿循环作为控制条件,通过不固结不排水、固结不排水、固结排水三轴剪切试验以及微结构试验,考虑干湿循环次数、干湿循环幅度、干密度、含水率等影响因素,主要研究了干湿循环作用下膨胀土、黄土、软土、黏性土、红土等不同土类的抗剪强度以及黏聚力和内摩擦角等宏观剪切特性以及微结构特性的变化规律。指出了目前研究中存在的问题,提出了进一步研究的建议。

干湿循环作用下土体的工程特性研究综述

在水利工程中,土坝的长期稳定性和结构安全十分重要,所以要对土体的工程特性进行研究。试验结果表明,干湿循环次数越多,不同土类的抗剪强度均在降低,土体的稳定性随着干湿循环的增加而降低,然后在达到一定次数后趋于稳定。通过对微观结构进行研究,从微结构角度解释了干湿循环对土体抗剪强度的影响。在此基础上,对今后的研究提出自己的看法。

Soil Physical and Chemical Properties of Five Subtropical Forests in Lingao of Hainan

With 5 types of typical forests as research object, the physical and chemical properties of different types of forests were analyzed by sample plot investigation method. The results showed that： the soil total porosity was the highest in the Casuarina equisetifolia forest （46.168%）, but the lowest in the Encalyptus robusta forest （39.46%）. The soil capillary porosity was the highest in the Acacia mangium forest （22.57%）, but the lowest in the secondary forest （18.95%）. The soil water content was the highest in the C. equisetifolia forest, with a mean value of 27.85%, but the lowest in the secondary forest, with a mean value of 4.34%. The soil pH values were in the range of 4.81-6.59, the soils in the A. mangium forest, C. equisetifolia forest and E. robusta forest were strongly acidic （pH 4.5-5.5）, and the soils in the secondary forest and C. nucifera forest were weakly acidic. The soils had organic matter contents in the range of 0.34-28.68 g/kg, and showed an order of A. mangium forest〉C. equisetifolia forest〉E. robusta forest〉secondary forest〉C. nucifera forest, with a decreasing trend with the soil depth increasing. The soil total N contents were in the range of 0.10-1.63 g/kg, the A. mangium forest showed the highest soil total N contents, while the C. nucifera forest exhibited the lowest soil total N contents; the soil total P contents were in the range of 0.21-1.74 g/kg, and the E. robusta forest had the highest soil total P contents; and the soil total K contents were in the range of 0.16-2.15 g/kg, and the A. mangium forest exhibited the highest soil total K contents. The soil available P contents were in the range of 0.98-132.46 mg/kg; and the secondary forests had the highest soil available P contents; and the soil rapidly available K contents were in the range of 3.03-27.35 mg/kg, and the C. nucifera forest exhibited the highest soil rapidly available K contents. The soil ammonium N contents were in the range of 1.38-5.15 mg/kg, and the nitrate N contents were in the range were in the range of 0.56 -3.51 mg/kg. The A. mangium forest showed the highest soil nitrate N contents （with a mean value of 2.29 mg/kg） and ammonium N contents （with a mean value of 3.93 mg/kg）. For the same forest type, with the increase of soil depth, the nitrate nitrogen and ammonium nitrogen content also showed a decreasing trend.