问题 单项选择题

某毛石砌体挡土墙,其剖面尺寸如题图所示。墙背直立,排水良好。墙后填土与墙齐高,其表面倾角为β,填土表面的均布荷载为q。

假定填土采用粉质黏土,其重度为19kN/m3(干密度大于1.65t/m3),土对挡土墙墙背的摩擦角δ=0.5 (为墙背填土的内摩擦角),填土的表面倾角β=10°,q=0。试问,主动土压力E(kN/m)最接近于下列()项数值。

A.60

B.62

C.70

D.74

答案

参考答案:B

解析:

查《地规》附录L图L.0.2挡土墙主动压力系数Ka(四):当a=90°时,Ka=0.26

按该规范第6.6.3条公式(6.6.3—1)计算:

问答题
单项选择题

Although there are many skillful Braille readers, thousands of other blind people find it difficult to learn that system. They are thereby shut (1) from the world of books and newspapers, having to (2) on friends to read aloud to them.

A young scientist named Raymond Kurzweil has now designed a computer which is a major (3) in providing aid to the (4) .His machine, Cyclops, has a camera that (5) any page, interprets the print into sounds, and then delivers them orally in a robot-like (6) through a speaker. By pressing the appropriate buttons (7) Cyclops’s keyboard, a blind person can "read" any (8) document in the English language.

This remarkable invention represents a tremendous (9) forward in the education of the handicapped. At present, Cyclops costs $ 50,000. (10) , Mr. Kurzweil and his associates are preparing a smaller (11) improved version that will sell (12) less than half that price. Within a few years, Kurzweil (13) the price range will be low enough for every school and library to (14) one. Michael Hingson, Director of the National Federation for the Blind, hopes that (15) will be able to buy home (16) of Cyclops for the price of a good television set.

Mr. Hingson’s organization purchased five machines and is now testing them in Maryland, Colorado, Iowa, California, and New York. Blind people have been (17) in those tests, making lots of (18) suggestions to the engineers who helped to produce Cyclops.

"This is the first time that blind people have ever done individual studies (19) a product was put on the market," Hingson said. "Most manufacturers believed that having the blind help the blind was like telling disabled people to teach other disabled people. In that (20) , the manufacturers have been the blind ones.

19()

A.after

B.when

C.before

D.as