问题 问答题 简答题

试从基本概念、计算公式及适用条件等方面比较压缩模量、变形模量与弹性模量,它们与材料力学中杨氏模量有什么区别?

答案

参考答案:

土的压缩模量Ε<sub>5</sub>的定义是土在侧限条件下的竖向附加应力与竖向应变之比值。

土的压缩模量是通过土的室内压缩试验得到的,

土的变形模量Ε<sub>0</sub>的定义是土体在无侧限条件下的应力与应变的比值。

土的变形模量时现场原位试验得到的,

土的压缩模量和变形模量理论上是可以换算的:。但影响因素较多不能准确反映他们之间的实际关系。

土的弹性模量Ε的定义是土体在无侧限条件下瞬时压缩的应力应变模量。

土的弹性模量由室内三轴压缩试验确定。

阅读理解

The bar-tailed godwit(斑尾鹬) has just broken its own record for the world’s longest non-stop flight, including humans in planes, according to a report made by Lund University Press. The bird can fly non-stop for eight days, while the most impressive man-made airplane can only remain in the sky for 82 hours without a stop.

The bar-tailed godwit’s journey, from Alaska to New Zealand, covers over 6,835 miles. It completes this trip twice a year, in autumn going to New Zealand, and in spring back to Alaska. The tireless bird ends the trip without stopping once for food or rest. All other birds can only finish trips that are twice as short as what the bar-tailed godwit travels.

One reason for the bar-tailed godwit’s success is that it has made the best use of its fuel, which is only 0.41 percent of its body weight over each hour of any given long flight. Hedenstrom, a professor from Lund University, says, “This figure is extremely low compared with other birds.” The bird also has a special body shape that helps it fly easily. It stores body fat and protein to manage its trips. It also travels fast, compared to other birds and animals.

Many questions remain about this bird record holder that never gets lost in the air. Researchers wonder whether it has an inside compass(指南针) that helps it to know the direction. Please watch how beautiful bar-tailed godwits look as they come in for a landing, along with other birds.

小题1:For the flight from Alaska to New Zealand, the bar-tailed godwit _____.

A.doesn’t need to stop to eat

B.is afraid of hot weather

C.seems very tired at last

D.should fly less than 7000 metres小题2:The main reason why the bar-tailed godwit can break the record is that it ______.

A.eats little food every hour

B.has a special body shape

C.stores much water in its body

D.has very light body weight小题3:The last paragraph tells us that ________.

A.researchers have understood the bird very well

B.the bird has a very good sense of direction

C.there are still many who doubt the bird’s ability

D.the bird has an inner compass小题4:What is the text mainly about?

A.A bird that breaks the record for the longest non-stop flight.

B.Birds and airplanes that can fly over a long distance.

C.Reasons for the bar-tailed godwit’s long-distance flight.

D.An introduction to long-distance flights of birds and humans.

多项选择题