问题 问答题 简答题

试述渠道防淤和清淤措施。

答案

参考答案:

(1)防淤措施。

①设置防沙、排沙设施,减少进入渠道的泥沙。②调整引水时间,避开沙峰引水。在高含沙量时,减少引水流量;在低含沙量时,加大引水流量。③防止客水挟沙入渠。防止山洪、暴雨径流进入渠道,避免渠道淤积。④衬砌渠道。减小渠道糙率,加大渠道流速,提高挟沙能力,减少淤积。

(2)清淤措施。

①水力清淤。在水源比较充足的地区,可在非用水季节,利用含沙量少的清水,按设计流量引入渠道,利用现有排沙闸、泄水闸、退水闸等泄水拉沙,按先上游后下游的顺序,有计划地逐段进行。②人工清淤。是目前使用最普遍的方法,在渠道停水后,组织人力,使用铁锹等工具,挖除渠道淤沙,一般一年进行1~2次。③机械清淤。主要是用挖泥船、挖土机、推土机等工程机械来清理渠道淤积泥沙。机械清淤速度快,效率高,降低劳动强度,节省大量劳力。

阅读理解

It's really true what people say about English politeness: it's everywhere.When squeezing past someone in a narrow aisle, people say "sorry".When getting off a bus, English passengers say "thank you" rather than the driver.In Germany, people would never dream of doing these things.

After all, squeezing past others sometimes can't be avoided.and the bus driver is merely doing his job.I used lo think the same way, without questioning it, until I started traveling to the British Isles and came to appreciate some more polite ways of communicating with people.

People thank each other everywhere in England, all the time.When people buy something in a shop, customer and retail assistant in most cases thank each other twice or more.In Germany, it would be exceptional to hear more than one thank you in such a conversation.British students thank their lecturers when leaving the room.English employers thank their employees for doing their jobs as opposed to Germans, who would normally think that paying their workers money is already enough.

Another thing I observed during my stay was that English people rarely criticize others.Even when I was working and mistakes were pointed out to me.my employers stressed several times but none of their explanations were intended as criticism.It has been my impression that by avoiding criticism, English people are making an effort to make others feel comfortable.This also is shown in other ways.British men still open doors for women, and British men are more likely to treat women to a meal than German men.However, 1 do need to point out here that this applies to English men a bit more than it would to Scottish men' Yes, the latter are a bit tightfisted.

小题1:What is the author's attitude towards English politeness?

A.He appreciates it

B.He gives no personal opinion

C.He thinks it is artificial

D.He thinks it goes too far.小题2:What can we learn about customers and retail assistants in Germany?

A.It's always a retail assistant who says thank you.

B.A customer never says thank you to a retail assistant.

C.They always say thank you to each other.

D.They may say thank you only once.小题3:We can learn from the last paragraph that Scottish men _____.

A.are more likely to be involved in a fighting.

B.are not so willing to spend money for women.

C.are more polite than English men.

D.treat women in a polite way.小题4:The author develops the text through the method of        .

A.giving comments

B.telling stories

C.making comparisons

D.giving reasons

单项选择题