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Wei X.,Key Laboratory of Arable Land Conservation Southwest China | Wei X.,Southwest University | Wei C.,Key Laboratory of Arable Land Conservation Southwest China | Wei C.,Southwest University | And 3 more authors.
Environment and Planning B: Planning and Design | Year: 2016

Uncertainty is a common feature of the present era. The plethora of uncertainties prompted frequent adjustment in the process of general land-use planning in China and, therefore, severely undermines the effectiveness of the entire land-use plan. Previous research mainly considered a macroanalysis of the causes, types, and treatments of the uncertainties, while research through case studies focusing on uncertainties are very rare. We analyzed the role of uncertainty in the general land-use planning schemes of the Jiangjin district of Chongqing Municipality, China, using the methods of comparative analysis and comprehensive induction. We discovered that the adjustments of the general land-use planning schemes consist of changes in land-use quota and layout, especially those of construction land. It can be found that the major internal uncertainties stem from the uncertainty of government action, base period, and technical specifications, while the major external uncertainties principally come from policy variation and economic development. The research results suggest that we need to further refine the land-use planning theory, optimize the land-use planning scheme, and strengthen the land-use planning legislation in order to decrease or eliminate the uncertainties so as to ensure the effectiveness of the general land-use plan. © 2015, © The Author(s) 2015.

Hu F.,Key Laboratory of Arable Land Conservation Southwest China | Hu F.,Southwest University | Wei C.,Key Laboratory of Arable Land Conservation Southwest China | Wei C.,Southwest University | And 6 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2013

Soil shear strength is one of the most important indicators in engineering design and soil erosion, also an essential parameter for soil precision tillage and design of agricultural machinery and equipment. In the previous work, although the shear strength of several types of soils has been investigated, few of these researches include that of purple paddy soils. Compared with purple soils, purple paddy soils have long been submerged in natural conditions; this special characteristic must have far-reaching influence on the mechanical properties of soils. Therefore, to investigate the water sensitivity of shear strength of purple paddy soils which are widely distributed over the Territorial Management Project in the Dazhu village, Qiantang town, Hechuan district in Chongqing, their shear strength was measured through triaxial test by considering the change of moisture directly, and accordingly some suggestions were put forward in dealing with purple paddy soil for engineering construction. In batch experiment, soil samples collected from the roadbed in the project were first air-dried, and after removal of visible pieces of plant debris and stones, all of the samples were ground to pass a 2-mm sieve for subsamples. According to test requirements, the water content of the subsamples was pre-adjusted to the required values carefully in preparation for triaxial compression test. Then unconsolidated undrained (UU) triaxial compression test was conducted under four different confining pressure (100, 200, 300, 400 kPa) using groups of samples at eight distinctive soil water contents (9%, 11%, 13%, 15%, 17%, 20%, 21% and 23%). The results indicated that: 1) The principal stress of purple paddy soils increases with the decrease of moisture under the same confining pressure, and the principal stress increases with the increasing confining pressure under the same water content, in which the increments become smaller with increasing soil water content. 2) When the water content of purple paddy soil is around a critical value, the variation of shear strength is slight; while the water content is above the critical value, the shear strength of purple paddy soils decrease with increasing water content. 3) The water content of purple paddy soil is of great significance on its cohesion. The number of cohesive strength peaks at 176.2 kPa at 13% and ends at 80.2 kPa at 23%. 4) The internal friction angle is negatively linearly correlated with soil water content (from 30.2° at 9% to 4.9° at 23%). This information confirms that purple paddy soils are water-sensitive, which is also beneficial to the reasonable design of local agricultural infrastructure.

Zhong S.-Q.,Southwest University | Zhong S.-Q.,Key Laboratory of Arable Land Conservation Southwest China | Zhong M.,Southwest University | Zhong M.,Key Laboratory of Arable Land Conservation Southwest China | And 6 more authors.
Journal of Mountain Science | Year: 2016

Soil shear strength is an important indicator of engineering design and an essential parameter of soil precision tillage and agricultural machinery and equipment design. Although numerous studies have investigated the characteristics of different soil shear strengths, only a few of these works have paid attention to soils containing considerable quantities of rock fragments. To date, most studies on the effects of rock fragments on the shear strength have paid attention to the role of rock fragments with sizes >2 mm. The effects of rock fragments <2 mm in soil are generally ignored. Similar to rock fragments >2 mm, the presence of rock fragments <2 mm could also change the mechanical properties of soils. Thus, in the present study we evaluated the potential influence of <2 mm rock fragments on soil shear strength via an unconsolidated undrained (UU) triaxial compression test. Our results were as follows: (1) A certain quantity of <2 mm rock fragments presented in purple soils developed from clay rocks; and an appropriate quantity of <2 mm rock fragments could improve the shear strength of soils. (2) The different PSDs of soils containing <2 mm rock fragments mainly caused variations in the internal friction angle of soils. (3) The shear strengths of the two mudstone-developed red-brown and gray-brown purple soils was more sensitive to water than that of the shale-developed coarse-dark purple soil. As the soil water content increased from 9% to 23%, the changes in the cohesion, internal friction angle, shear strength, and the maximum principal stress difference were smaller in the coarse dark purple soil than in the two other soils. We therefore concluded that <2 mm rock fragments in purple soils exerted important effects on soil shear strength. A better understanding of the differences among the shear strength features of purple soils could help improve the design of agricultural machinery and equipment. © 2016, Science Press, Institute of Mountain Hazards and Environment, CAS and Springer-Verlag Berlin Heidelberg.

Shouqin Z.,Key Laboratory of Arable Land Conservation Southwest China | Shouqin Z.,Southwest University | Chaofu W.,Key Laboratory of Arable Land Conservation Southwest China | Chaofu W.,Southwest University | And 8 more authors.
International Journal of Agricultural and Biological Engineering | Year: 2015

The paddy fields and water storage facilities are seriously damaged by the coal mine subsiding in the hilly post-mining and subsidence-stable areas in China, which make the farmers there being suffered greatly from the lack of water for traditional rice cultivation and daily life. The purpose of this paper is to find a method to restore the damaged paddy fields, thereby promoting sustainable development of land resources, and alleviating the contradiction between people and land, as well as creating a more inhabitable environment. The research methodology included field experiments, cultivated observation, and field investigation. This paper selected the Songzao Mining Area as the research area, and focused on the restoration technologies of damaged paddy fields, through the following four different measures at three experimental fields: (1) Traditional repeated cattle plowing (CK); (2) Water retention agent with repeated cattle plowing (W&C); (3) Film without holes under tilth depth (FO); and (4) Film with holes under tilth depth (FW). At last, a contrastive analysis of the four measures was made according to the results of the experiments. The results show that the use of water retaining agent with repeated cattle plowing (W&C) can be the most appropriate method to restore the damaged paddy field in the hilly post-mining and subsidence-stable area in southwest China. Compared with the other three measures, its water productivity is the maximum (0.81 kg/m3), and the net income is the highest (1 403 $/hm2). What’s more, it is simple, short time-consuming, and low cost, which is benefit to generalize the use of this restoration technology. © 2015, Chinese Society of Agricultural Engineering.

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