造林整地排水产生水土流失及其防止措施

造林整地排水产生水土流失及其防止措施［英］Ｐ．Ａ．ＣａｒｔｉｎｇＭ．Ｓ．ＧｌａｉｓｔｅｒＴ．Ｐ．Ｆｌｉｎｔｈｅｍ１引言英国高地造林整地的常规方法是采用顺坡和横坡开沟相结合的办法进行翻耕排水。现已制订有森林排水网路的设计准则及河道管理准则，遵循这些准则...

Study on construction schemes of Three Gorges RCC dam

Study is further carried out on construction schemes of partial dam body of Three Gorges Project to adopt RCC during technical design stage.Analysis and comparisons show that with adopting RCC,the total construction time taken may be 3 months shorter than preliminary design stage,and the time of concrete placing to the top of the dam may be 4 months ahead of schedule. However,the annual peak intensity of concrete placement would increase from 4.1 million m3 of conventional concrete to present 4. 83 million m3,and monthly peak intensity from 460 thousand m3 to 539 thousand m3. The occurrence time of peak intensity will be ahead of the original target date. The construction of C'Oncrete will become more unbalanced.For adopting RCC in construction of partial Three Gorges dam body,four RCC placement schemes are studied preliminarily, of which two schemes ate recommended:the one is that the dam body below elevation of 120 m will be placed by using U. S.Rotec tower crane infullset,above elevation of 120 m using high-framed portal cranes;the another is that the dam body below elevation of 53m will be placed by using heavy creter cranes(or dump trucks directly to the placing area),above elevation of 53 m using heavy tower cranes.For cautiousness,it is suggested that the key equipments of above two schemes,i. e.specific tower crane,and heavy creter crane 4 must be productively used in first-stage works before they will be used in concrete placement of Three Gorges dam' With partial dam body to adopt RCC,because of increment of concrete placement intensity,the capacity of mixer plant must be also increased,while the capacity of cooling plant is still equivalent to one of conventional concrete scheme.