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问题 多项选择题

当涵洞洞底纵坡为6%时，通常采用的设计方案是( )。

A．洞底顺直，基础底部不设防滑横墙

B．洞底顺直，基础底部加设防滑横墙

C．基础做成连续阶梯形

D．设置跌水井

E．基础分段做成阶梯形

答案

参考答案：B,C

解析： 第一幸工程构造第三节桥梁与涵洞工程：涵洞的构造。
[思路] 涵洞的洞底应有适当的纵坡，其最小值为0.4%，一般不宜超过5%，涵洞的纵坡不宜过火，以免管壁受急流冲刷。当洞底纵坡大于5%时，其基础底部宜每隔3～5m设防滑横墙，或将基础做成阶梯形；当洞底纵坡大于10%时，涵洞洞身及基础应分段做成阶梯形，并且前后两段涵洞盖板或拱圈的搭接高度不得小于其厚度的1/4。
[易错] 本题易错项为选项D。该选项很像标准答案，考生很容易选错。
[拓展] 考生要注意桥梁与涵洞的区别。
根据桥梁跨径总长乙和单孔跨径L0的不同，桥梁可分为
特大桥：L≥500m或L0≥100m
大 桥：L≥100m或L0≥40m
中 桥：100m＞L＞30m或40m＞L0≥20m
小 桥：30m≥L≥8m或20m＞L0≥5m
涵 洞：L＜8m或L0＜5m(圆管涵及箱涵无论孔径大小、孔数多少，都称为涵洞)

单项选择题

Passage twoEducating girls quite possibly yields a higher rate of return than any other investment available in the developing world .women’s education may be unusual territory for economists ,but enhancing women’s contribution to development is actually as much an economic as a social issue .and economics ,with its emphasis on incentives ,provides guideposts that point to an explanation for why so many girls are deprived of an education Parents in low-income countries fail to invest in their daughters because they do not expert them to make an economic contribution to he family :girls grow up only to marry into somebody else’s family and bear children .Girls are thus seen as less valuable than boys and kept at home to do housework while their brothers are sent to school-the prophecy becomes self-fulfilling ,trapping women in a vicious circle of neglect. An educated mother ,on the other hand ,has greater earning abilities outside the home and faces an entirely different set of choices. She is likely to have fewer but healthier children and can insist on the development of all her children ,ensuring that her daughters are given a fair chance .The education of her daughters then makes it much more likely that the next generation of girls ,as well as of boys ,will be education and healthy . The vicious circle is thus transformed into a virtuous circle. Few will dispute that education women has great social benefits.But it has enormous economic advantages as well .Most obviously ,there is the direct effect of education on the wages of female workers.Wages rise by 10 to 20 percent for each additional year of schooling. Such big returns are impressive by the standard of other available investments ,but they are just the beginning .Education women also has a significant impact on health practices,including family planning.

The author argues that educating girls in developing countries is ( )

A．troublesome

B．labor –saving

C．rewarding

D．expensive
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判断题

秦朝灭亡后，经过四年的楚汉战争，刘邦战胜了项羽，于公元前202年建立了汉朝，定都长安，历史上称为西汉。
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