• Environmental Engineering Research
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• 제20권1호
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• pp.19-24
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• 2015

This paper mainly focuses on the research of the monitoring data about the total nitrogen (TN), total phosphorus (TP) of ten monitoring points of Hongze Lake in 28 years. Our study adopts the technical methods such as difference comparison, correlation analysis, Mann-Kendall, etc. to analyze the statistical characteristics, regional differences, and temporal and spatial variation condition of ten monitoring points of Hongze Lake in 1986-2013 as well as the reason for the time and space variation of TN and TP. The results show that the TN and TP of Hongze Lake change dramatically during the period of 1994-2004. In all the monitoring periods, TN and TP of the HZ5, HZ6, HZ7, HZ8 monitoring points in the estuary surrounding the Huaihe River are the highest, which suggests that TN and TP of Hongze Lake should not be ignored for the pollution along the Huaihe River. The TN concentration in the core area is the highest, but that in the development control area is the lowest. In most of the years, TN concentration is higher than 2 mg/L, and the water quality is V class and poor V class water quality in China's Environmental Quality Standards for Surface Water (GB3838-2002). TP concentration of the three areas is basically close, that is lower than 2 mg/L in most of the years, and the water quality is within the V class. The TN and TP concentration of Hongze Lake decreased and intensifying trend of eutrophication is controlled after 2004.

• Earthquakes and Structures
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• 제24권4호
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• pp.275-288
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• 2023

Based on the crucial role of high-speed railway bridges (HSRBs) in the safety of high-speed railway operations, it is an important approach to mitigate earthquake hazards by proceeding with seismic risk assessments in their whole life. Bridge seismic risk assessment, which usually evaluates the seismic performance of bridges from a probabilistic perspective, provides technical support for bridge risk management. The seismic performance of bridges is greatly affected by the degradation of material properties, therefore, material damage plays a nonnegligible role in the seismic risk assessment of the bridge. The effect of material damage is not considered in most current studies on seismic risk analysis of bridges, nevertheless. To fill the gap in this area, in this paper, a nonlinear dynamic time-history analysis has been carried out by establishing OpenSees finite element model, and a seismic vulnerability analysis is carried out based on the incremental dynamic analysis (IDA) method. On this basis, combined with the site risk analysis, the time-dependent seismic risk analysis of an offshore three-span HSRB in the whole life cycle has been conducted. The results showed that the seismic risk probabilities of both components and system of the bridge increase with the service time, and their seismic risk probabilities increase significantly in the last service period due to the degradation of the material strength, which demonstrates that the impact of durability damage should be considered when evaluating the seismic performance of bridges in the design and service period.

• Geomechanics and Engineering
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• 제32권3호
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• pp.347-359
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• 2023

With the development of infrastructure, there is a critical shortage of filling materials all over the word. However, a large amount of silt accumulated in the lower reaches of the Yellow River is treated as waste every year, which will cause environmental pollution and waste of resources. Microbial induced calcium carbonate precipitation (MICP) technology, with the advantage of efficient, economical and environmentally friendly protection, is selected to solidify the abandoned Yellow River silt with poor mechanical properties into high-quality filling material in this paper. Based on unconfined compressive strength (UCS) test, determination of calcium carbonate (CaCO₃) content and scanning electron microscope (SEM) test, the effects of cementation solution concentration, treatment times and relative density on the solidification effect were studied. The results show that the loose silt particles can be effectively solidified together into filling material with excellent mechanical properties through MICP technology. The concentration of cementation solution have a significant impact on the solidification effect, and the reasonable concentration of cementation solution is 1.5 mol/L. With the increase of treatment times, the pores in the soil are filled with CaCO₃, and the UCS of the specimens after 10 times of treatment can reach 2.5 MPa with a relatively high CaCO₃ content of 26%. With the improvement of treatment degree, the influence of relative density on the UCS increases gradually. Microscopic analysis revealed that after MICP reinforcement, CaCO₃ adhered to the surface of soil particles and cemented with each other to form a dense structure.

• Geomechanics and Engineering
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• 제17권3호
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• pp.307-316
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• 2019

Dam deformation should be strictly controlled for the construction of 300 m-high rockfill dams, so the rockfill materials need to have low porosity. A method of using composite grout is proposed to reduce the porosity of rockfill materials for the construction of high rockfill dams. The composite grout is a mixture of fly ash, cement and sand with the properties of easy flow and post-hardening. During the process of rolling compaction, the grout admixture sprinkled on the rockfill surface will gradually infiltrate into the inter-granular voids of rockfill by the exciting force of vibratory roller to reduce the porosity of rockfill. A visible flowing test was firstly designed to explore the flow characteristics of composite grout in porous media. Then, the compressibility, shear strength, permeability and suffusion susceptibility properties of composite grout-modified rockfill are studied by a series of laboratory tests. Experimental results show that the flow characteristics of composite grout are closely related to the fly ash content, the water-to-binder ratio, the maximum sand size and the content of composite grout. The filling of composite grout can effectively reduce the porosity of rockfill materials, as well as increase the compression modulus of rockfill materials, especially for loose and gap-graded rockfill materials. Composite grout-modified rockfill tends to have greater shear strength, larger suffusion erosion resistance, and smaller permeability coefficient. The composite grout mainly plays the roles of filling, lubrication and cementation in rockfill materials.

• Advances in concrete construction
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• 제16권3호
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• pp.141-153
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• 2023

In order to develop and take full advantage of pasture fiber and waste concrete, this article studied how different amounts of pasture fiber influenced the toughness and pore structure of concrete with different replacement rates of recycled fine aggregate. Pasture fiber recycled concrete constitutive equations were established under idealized stiffness and toughness damage rate, based on fracture energy and damage mechanics theories. The relationship between pore structure and toughness was studied utilizing nuclear magnetic resonance and fractal theory. The toughness of text groups (0% (JZ), 10% (ZS10), 20% (ZS20)) first increased and then decreased with increasing amounts of pasture fiber, based on the damage rate of toughness. The toughness of concrete samples with recycled fine aggregate and pasture fiber is negatively correlated to the fractal dimension of small and medium-sized pores with a pore size of 0-500 nm. At a replacement rate of 10% of the recycled fine aggregate, the fractal dimension of the air voids (r: 500-9000 nm, i.e., Lg(r) ∈ [2.7, 3.9]) shows a gradual decrease with the increase of grass fiber dosage, indicating that with such a replacement rate of the recycled fine aggregate, the increase of pasture fiber can reduce the complexity of the pore structure of the air voids (500-9000 nm).

• Geomechanics and Engineering
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• 제36권6호
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• pp.631-640
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• 2024

In the traditional slope stability analysis, ignoring the spatial variability of slope soil will lead to inaccurate analysis. In this paper, the K-L series expansion method is adopted to simulate random field of soil strength parameters. Based on Random Limit Equilibrium Method (RLEM), the influence of variation coefficient and fluctuation range on reliability of soil slope supported by micro-pile is investigated. The results show that the fluctuation ranges and the variation coefficients significantly influence the failure probability of soil slope supported by micro-pile. With the increase of fluctuation range of soil strength parameters, the mean safety factor of the slope increases slightly. The failure probability of the soil slope increases with the increase of fluctuation range when the mean safety factor of the slope is greater than 1. The failure probability of the slope increases by nearly 8.5% when the fluctuation range is increased from δ_v=2 m to δ_v =8 m. With the increase of the variation coefficient of soil strength parameters, the mean safety factor of the slope decreases slightly, and the probability of failure of soil slope increases accordingly. The failure probability of the slope increases by nearly 31% when the variation coefficient increases from COV_c=0.2, COV_φ=0.05 to COV_c=0.5, COV_φ=0.2.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회(2)
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• pp.1031-1032
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• 2005

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.217-226
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• 1993

As results of not selecting and using farm well pump properly , it's running regime is far away from high efficient zone and running efficiency of farm well pump is lower. The paper analyses unhealthy tendencies of technical state of diving-electric pump, deep well and centrifugal pump which are commonly used in our country. The paper also summarizes several technical innovation plans to raise efficiency : stage change plan, diameter change plan, speed change plan and synthetic technical innovation . Each plan gives a detailed introduction of designing and construction manners, through practical measuring , the synthetic efficiency of innovated well pumps raise above 30 percent. Economic benefit is evident.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.257-262
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• 1996

Large amount of water is diverted annually for irrigation along the Yellow River. Owing to the tremendous sediment carried by the river , sediment deposits is an important problem in irrigation and drainage system. The sediment has to be taken out by machines from the irrigation system, otherwise water can not be available in the right place at the right time. In order to improve the sediment desilting efficiency, the sediments that settle in certain sites of a irrigation system must be removed by different desilting machines with special performance and working conditions. Those certain sites include : the diversion canal in the flood plain , the mouth of inlet, settling basin , irrigation and drainage system. In view of removal sediment above, the paper presents the ideas of type selection of desilting machines applied to certain sites. Proposals of making further improvement on performance for some desilting machines are also put forward.

• Korean Journal of Chemical Engineering
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• 제35권11호
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• pp.2296-2302
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• 2018

Internally plasticized PVC was prepared via chemical reaction of azide PVC and alkynyl group containing castor oil methyl ester. The chemical structure of alkynyl group containing castor oil methyl ester and internally plasticized PVC was characterized with FT-IR and $^1H$ NMR. Properties of internally plasticized PVC, including thermal stability, tensile tests and resistance to extraction in different solvents, was investigated. The results showed that alkynyl group containing castor oil methyl ester, as internal plasticizer of PVC, not only decreased the $T_g$ of PVC from $84.6^{\circ}C$ to $41.6^{\circ}C$ efficiently, but also presented no plasticizer loss in five different solvents. The tensile tests showed that elongation at break and tensile strength of internally plasticized PVC was 353.8% and 18.1 MPa. The internally plasticized PVC has potential application in replacing the traditional PVC material in PVC products with high durability.