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问题 单项选择题

有一截面积为0.4m×0.4m的预制方桩(C30)，桩长18m，桩顶面在地面下4m处，地面下土层分布情况：0～6m为粉质黏土，qak=26kPa；6～12.5m为粉土，qsik=30kPa；黏粒含量为1.5%；12.5～20m为粉砂，qsik=36kPa；20～23m为砾砂，qsik=52kPa，qpk=3200kPa，地下水位1.5m，试回答以下问题：

若粉土和粉砂发生液化，且在11m处标贯击数N=9，18m处标贯击数N=18，地下水位3.5m，8度地震区，当按桩承受全部地震作用时，单桩竖向抗震承载力特征值与（）最为接近。

A．577kN

B．356kN

C．486kN

D．684kN

答案

参考答案：A

解析：

当桩承受全部地震作用：

糊士和粉砂发生液化时：

在11m处Ncr=N0[0.94+0.1(ds-dw)]=10[0.94-0.1(11-3.5)]=16.59/16.5=0.55＜0.6查《建筑抗震设计规范》(GB 50011—2001)表4．4．3，得其折减系数为：1/3；

在18m处Ncr=N0[0.94-0.1(ds-dw)]=10[0.9+0.1(18-3.5)]=23.518/23.5=0.77查《建筑抗震设计规范》(GB 50011—2001)表4．4．3，得其折减系数为2/3，

所以：

Quk=4×0.4(2×26+6.5×30×+7.5×36××2×52)+3200×0.42=1153.6kN

考虑液化时单桩竖向承载力特征值为：

RaE=Quk/2=1153.6/2=576.8kN

单项选择题

一般来说，机床安装时导轨的精度主要由（）来保证。

A、加工

B、检验

C、测量

D、调整
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单项选择题

I will always remember my mother’s last few days in this world.

On February 14th, 2000, my class went on a field trip to the beach. I had so much fun. When we returned to school, my teacher told me to go to the headmaster’s office. When I got into the office, I saw a police officer. Suddenly I realized something was wrong. The police officer told me what had happened and we went to pick my sister up. After that, we went to the hospital and waited. Time went slowly. Finally, we got to see our mother. It was terrible.

On the next day, the headmaster came and told my two teachers what had happened. I was taking a rest that day. I knew it had something to do with my mother. I kept thinking that she either died or had gotten better. How I wished that she had gotten better. When my teacher took me outside, my sister ran up to me. She started crying, "She’s gone. Teresa, mommy’s gone. She’s dead. " I couldn’t believe it. We jumped into the car and drove straight to the hospital. Most of my family were there. The silence was terrible. I knew I had to say goodbye.

Today when I look back, I still miss my mother very much, but I know that I will live. My mother was a p mother, who had the biggest heart. My mother was an angel walking on the earth. I will always remember her as living. When someone is asked who their hero is, they usually say someone famous, like Michael Jordan or Britney Spears. When someone asks me who my hero is, I tell them, my mother. My mother lives every day. That is what makes her at rue hero.

Who brought the writer the bad news that her mother was ill().

A．Her sister.

B．The headmaster.

C．Her teacher.

D．The police officer.
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