| In order to improve the water quality and ensure the normal flood discharge capacity and the smooth flow of waterways of rivers and lakes,we carry out large-scale river and lake dredging projects every year.which will produce a lot of dredged sludge.At the same time,with the rapid development of coastal engineering and port construction,it also produced a considerable number of marine dredged sludge.Dredged sludge mainly composed of clay,with the properties of high water content which is difficult to dehydration,low strength,poor soil mechanical.and contains a certain toxic and harmful pollutants.And due to the growing shortage of urban land resources and people’s awareness of environmental protection,the original sludge disposal methods to throw sludge and landfill are likely to lead to a series of pollution and urban environmental geotechnical problems,has been unable to adapt to the rapid development of the city.Therefore,through the resource management of dredged sludg,e,can solve the problem of sludge disposal,on the other hand,can also provide materials for the engineering field,ease the tension of building materials resources,which is in line with China’s national conditions of one of the sludge disposal.However,the utilization of dredged sludge is also faced with the problem of low dewatering efficiency and low post-stage strength and has become a hot and difficult topic in related fields.Therefore,in view of the difficult problems such as dewatering difficulty and poor mechanical property in the process of dredged sludge utilization,this paper proposes to apply the newly developed fiber reinforced technology to dredged sludge treatment.A series of laboratory tests were carried out to systematically study the effect of fiber reinforced technology on the pre-dewatering and enhancement effect of dredged sludge,and the mechanism of fiber reinforced technology was analyzed.The paper has mainly obtained the following achievements:(1)A series of dry evaporation tests were carried out on the fiber reinforced dredged sludge.The effects of uber reinforced technology on the process of dredging sludge evaporation and fissure development were studied.The results show that the rate of evaporation of dredged sludg,e can be increased by the fiber reinforcement,and the evaporation rate increases with the increase of fiber content.On this basis,the quantitative relationship between evaporation rate and time is established.In addition,it was found that the fiber can effectively inhibit the development ot dredging mud fissures during the evaporation process.(2)A series of consolidation compression tests were carried out on the fiber reinforced dredged sludge.It was found that the incorporation of fiber could increase the compression,vold ratio,compression coefficient.consolidation coefficient and hydraulic conductivity of sludge in the consolidation process,and improve the sludge consolidation effect and consolidation efficiency.The consolidation effect of sludge increases with the increase of fiber content,and the optimal fiber content is 0.1%.(3)A series of direct shear tests were carried out on the fiber reinforced dredged sludge.The effects of fiber content on the moisture content,dry density and strength of the sludge were studied under differentt consolidation pressures.It was found that the moisture content decreased firstly and then increased with the increase of fiber content,and the dry density is increased first and then decreased,the optimum content is 0.1%.While the shear strength of the sludoe increases close to the linear with the increase of fiber content.And the shear strength of sample with the tiber content of 0.8%is 1.48,1.58,1.42.1.27 times the sample which is non-reinforccd respectively under the consolidation pressure of 50,100.200 and 400kPa,and the reinforcement efficiency is the most significant under the pressure of 100kPa.In addition,the low moisture content and high density conditions improves the fiber enhancement effect.(4)By adding cement and fly ash in the fiber reinforced dredged sludge.and a series of unconfined compression tests were carried out on the samples.The effects of fiber content,curing agent,fiber content and initial moisture content on the unconfined compressive strength after sludge solidification were studied,and analyzed the stress-strain characteristics and failure process of the specimen.The results show that the unconfined compressive strength of the solidified sludge increases firstly and then decreases slightly with the increase of fiber content,and the optimal fiber content is 0.1%.With the increase of the cement content,the unconfined compressive strength of the solidified sludge increased significantly,while the fly ash content was too high.the strength decreased.With the increase of fiber content,the greater the damage strain of sludge,the higher the residual strength,and the fiber can improve the brittle failure mode of the solidified sludge.While the cement content is relatively high,it is brittle when the sludge is damaged,when the fly ash content is relatively high,the damage strain decreases.(5)The dry evaporation test and the unconfined compressive strength test were carried out on the fiber reinforced dredged sludge.and the variation law of the strength of the sample in the drying path was studied.The results showed that the strength of sludge increased with the decrease of water content,when the moisture content of solidified sludge is reduced from 45%to 5%,the strength is increased by about 3 times,and close to the linear increase.And the unconfined compressive strength of solidified sludge increases firstly and then decreases slightly with the increase of fiber content with the optimum fiber content is 0.1%.With the decrease of water content,fiber reinforced technology to enhance the strength of solidified sludge is increasing,the reinforcement effect is more significant(6)The mechanism of fiber reinforced technology is analyzed.The effect of fiber on sludge drainage is mainly due to the role of the bridge,which providing a channel for the removal of moisture in the sludge.The increase of the strength of dredged sludge is mainly due to the fact that the discrete fibers distributed in the sample can bear some tensile stress,effectively share the external load and restrain the deformation of the specimen.The reinforcing effect of the fiber depends mainly on the cohesion and friction of the interface.(7)The fiber reinforced technology proposed in this paper can improve the early dewatering efficiency of sludge and improve the mechanical properties of sludge.The technology is simple and practical,affordable,with a certain degree of engineering application value. |
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