某土石坝坝基表层土的平均渗透系数为k1=10-5cm/s，其下的土层渗透系数为k2=10-3cm/s，坝下游各段的孔隙率见表，设计抗渗透变形的安全系数采用1.75，试判断实测水力比降大于允许渗透比降的土层分段。
参考答案：
根据《水利水电工程地质勘察规范》(GB 50487-2008)土的渗透变形判别的土允许水力比降的确定，流土型的流土临界水力比降为
Jcr=(Gs-1)(1-n)
式中：Jcr——土的临界水力比降；
Gs——土的颗粒密度与水的密度之比；
n——土的孔隙率(%)。
Ⅰ段
Jcr=(Gs-1)(1-n)=(2.7-1)×(1-0.524)=0.8092
允许渗透比降
。
Ⅱ段
Jcr=(2.7-1)×(1-0.535)=0.7905
允许
。
Ⅲ段
Jcr=(2.72-1)×(1-0.524)=0.8187
允许
。
Ⅳ段
Jcr=(2.7-1)×(1-0.545)=0.7735
允许
。
所以Ⅳ段实际水力比降大于允许渗透比降。
| 完形填空。 | |||
| The hardworking blacksmith John used to work all day in his shop and so hard working was he that at times he would make the sparks fly from his hammer. The son of Mr. Smith, a rich neighbor, __1__ come to see the blacksmith every day and for hours and hours he would enjoy himself __2__ how the tradesman worked. "Young man, why don't you try your __3__ at making shoe tacks, even if it is only to __4__ the time?" said the blacksmith. "Who knows, one day, it may be of __5__ to you." The boy began to see what he could do. After a little __6__ he found that he was becoming very __7__ and soon he could make some of the finest tacks. Old Mr. Smith died and the son on __8__ of the war lost all his property. He had to leave home and was forced to __9__ residence in another country. It so __10__ that in this village there were numerous shoemakers who were spending a lot of money to buy __11__ for their shoes and at times even __12__ they paid high prices they were not able to get what they wanted, because in that part of the country there was a high __13__ for soldiers' shoes. Our young Mr. Smith, who was finding it difficult to __14__ his daily bread, remembered that once upon a time he had learned the art of making tacks(鞋钉)and had a sudden __15__ of making a bargain with the shoemakers. He told them that he would make the tacks if they would help him __16__ a workshop. The shoemakers were only too glad of the __17__. And after a while, Mr. Smith found that he was making the finest tacks in the __18__. "How __19__it seems," he used to say, "Even making tacks can bring a __20__. My trade is more useful to me than all my former property." | |||
| ( )1. A. used to ( )2. A. seeing ( )3. A. energy ( )4. A. save ( )5. A. danger ( )6. A. practice ( )7. A. surprised ( )8. A. term ( )9. A. take over ( )10. A. happened ( )11. A. metal ( )12. A. as ( )13. A. demand ( )14. A. eat ( )15. A. request ( )16. A. open ( )17. A. offer ( )18. A. valley ( )19. A. fascinating ( )20. A. career | B. had to B. watching B. luck B. lose B. interest B. message B. skilled B. top B. take down B. occurred B. tacks B. why B. price B. earn B. suggestion B. settle B. requirement B. village B. satisfactory B. change | C. wanted to C. staring C. hand C. pass C. use C. revision C. satisfied C. account C. take off C. charged C. furs C. how C. praise C. make C. opinion C. close C. order C. country C. funny C. fortune | D. needed to D. looking D. way D. devote D. importance D. promotion D. determined D. behalf D. take up D. adapted D. cloth D. though D. call D. dry D. idea D. locate D. arrangement D. world D. strange D. job |