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Yumei Li ¹, Hao Feng ², Zhen Wang ³

Affiliations
1 College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling 712100, Shaanxi, CN
2 Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling 712100, Shaanxi, CN
3 China Institute of Water Resources and Hydropower Research, Haidian District, Beijing, CN

Abstract

The direct straw incorporation to soils can lead to problems of slow decomposition, diseases and pests, and nitrogen immobilization by microorganisms competing with crop uptake. We examined how straw pretreatments (either comminution, addition of liquid urea or blending with ferric hydroxide) aimed at decreasing these risks affected aggregation, bulk density, porosity and water evaporation of amended soils. Results showed that comminuted and urea treated straw significantly improved soil aggregation and increased soil porosity. Whereas a direct incorporation of straw had no impact on aggregate stability or porosity. Pretreatment of the straw doubled the MWD measured with wet sieving method and increased porosity by up to 12%; the application of ferric hydroxide effectively improved soil porosity distribution and further controlled the soil water evaporation; the combined application of ferric hydroxide and straw had a better effect on soil water conservation. The above results provided a theoretical basis for the selection of an optimal straw-returning method.

Keywords

Straw Pretreatment, Aggregate, Soil Structure, Evaporation.

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Yumei Li ¹, Hao Feng ², Zhen Wang ³

Affiliations
1 College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling 712100, Shaanxi, CN
2 Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling 712100, Shaanxi, CN
3 China Institute of Water Resources and Hydropower Research, Haidian District, Beijing, CN

Abstract

The direct return of straw to soils can lead to problems of slow decomposition, disease and pest occurrence, and nitrogen immobilization by microorganisms competing with crop uptake. In this study, we have examined straw pretreatments (comminution, addition of liquid ammonia and blending with ferric hydroxide) that can be applied before returning it to the soil. We have conducted a laboratory experiment to investigate the effects of these treatments on soil water content, water-holding capacity and soil water characteristic curves. Finely-cut straw (powdery) increased soil saturated water content and improved soil water-holding capacity and water-supplying capacity, while long-cut straw (2 cm long) had smaller effects on these properties and comminuted-ammoniated straw led to a significant increase in these properties. Finely-cut straw and long-cut straw both led to rapid soil dehydration, while for the ammonia-amended straw and straw blended with ferric hydroxide the dehydration rate was lower. The above results provide a basis for the selection of the novel and efficient methods for returning straw to soils.

Keywords

Straw Pretreatment, Water-Holding Capacity, Dehydration, Rate Evaporation.

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Rui Jing ¹, Jingfu Kang ¹, Zhaowei Shen ¹, Zhen Wang ¹, Dazhi Wang ¹

Affiliations
1 School of Civil Engineering, Key Laboratory of Coast Civil Structure Safety (Tianjin University), Ministry of Education, Tianjin University, Tianjin-300072, CN

Abstract

In this paper, based on theory of elastic mechanics, the mechanical property of prestressed concrete lining structure was studied;theoretical formulas of normal displacement and inner force on the middle surface were deduced and the area of adjacent anchor effect was determined. Combing observed data in practical project, the theoretical result in the area of adjacent anchor effect and measured result of circumferential stress in prestressed concrete lining structure was compared. Results reveal that the theoretical results given by the formulas of adjacent anchor effect are in very agreement with the field test, the theoretical results being reasonable. The calculating method of the adjacent anchor effect in the prestressed tunnel liner with circular anchored tendons presented in the paper can be used in practical project.

Keywords

Prestressed Concrete Liner, Elastic Theory, Adjacent Anchor Effect, Measured Data.

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