[不定项选择题]试述超声波透射法现场检测基桩完整性原理及现场检测技术。 下列结果分析中不正确的表述有()。 A.声速临界值采用混凝土声速平均值与2倍声速标准差之差
A.波幅异常时的临界值采用波幅平均值减6D
B.
C.实测混凝土声速平均值低于声速临界值时，可将其作为可疑缺陷区域
D.当PSD值在某点附近变化明显时，可将其作为可疑缺陷区域

[不定项选择题]试述超声波透射法现场检测基桩完整性原理及现场检测技术。 现场测试工作正确的是()。
A.发射和接收换能器分别置于两声测管的同一高度，自下而上，将收发换能器以相同步长(不大于200mm)向上提升，进行水平检测
B.若平测后，存在桩身质量的可疑点，则进行加密平测，以确定异常部位的纵向范围
C.斜测时，发、换能器中心线与水平夹角一般取30°～40°
D.扇形测在桩顶、桩底斜侧范围受限或减小换能器升降次数时采用

[不定项选择题]试述超声波透射法现场检测基桩完整性原理及现场检测技术。 根据《公路工程基桩动测技术规程》)(JTG/TF81-01-2004)规定，关于仪器设备要求正确的有()。 A.声波发射脉冲为阶跃或矩形脉冲，电压最大值不小于1000V
A.换能器沿径向无指向性
B.换能器谐振频率为1kHz～200kHz
C.换能器在1MP
D.水压下能正常工作

[不定项选择题]试述超声波透射法现场检测基桩完整性原理及现场检测技术。 声波在混凝土传播过程中，当桩身混凝土介质存在阻抗差异时，将产生()造成声波能量的吸收、衰减，通过声学参数或波形变化来检验桩身混凝土是否存在缺陷。
A.反射波、绕射波、折射波
B.声时、波幅变化
C.透射波、吸收波
D.接收波主频变化

[不定项选择题]试述超声波透射法现场检测基桩完整性原理及现场检测技术。 声侧管理设要求正确的是()。 A.声管内径应大于换能器外径
A.声测管管口应高出桩顶100mm-300mm，且各声测管管口高度应一致
B.《公路工程基桩动测技术规程》)(JTG/TF81-01-2004)规定、桩径
C.不大于1600mm时，埋设三根管：当桩径大于1600mm时，应埋设四根管
D.《建筑基桩检测技术规范》(JGJ106L-2014)规定、桩径小于或等于800mm时，不少于2根声测管，桩径大于800mm且小于或等于1600mm时，不少于3根声测管：桩径大于1600mm时，不少于4根声测管：桩径大于2900mm时，宜增加预埋声测管数量

[不定项选择题]共用题干 Animal's “Sixth Sense”
A tsunami（海啸）was triggered（引发）by an earthquake in the Indian Ocean in December, 2004.It killed tens of thousands of people in Asia and East Africa. Wild animals,1， seem to have escaped that terrible tsunami. This phenomenon adds weight to notions that they possess a“sixth sense” for2 ,experts said.
Sri Lankan wildlife officials have said the giant waves that killed over 24,000 people along the Indian Ocean island's coast clearly 3 wild beasts,with no dead animals found.
“No elephants are dead,not4a dead rabbit. I think animals can5 disaster.
They have a sixth sense. They know when things are happening,” H. D. Ratnayake,deputy director of Sri Lanka's Wildlife Department,said about one month after the tsunami attack. The6washed floodwaters up to 2 miles inland at Yala National Park in the ravaged（被 毁坏的）southeast, Sri Lanka's biggest wildlife7and home to hundreds of wild elephants and several leopards（豹）.
“There has been a lot of8 evidence about dogs barking or birds migrating before volcanic eruptions（火山爆发）or earthquakes. But it has not been proven ,” said Matthew van Lierop,an animal behavior 9 at Johannesburg Zoo.
“There have been no10studies because you can't really test it in a lab or field setting , ” he told Reuters. Other authorities concurred（同意）with this11.
“Wildlife seem to be able to pick up certain12 ,especially birds…there are many re- ports of birds detecting impending（迫近的）disasters , ” said Clive Walker , who has written several books on African wildlife.
Animals13 rely on the known senses such as smell or hearing to avoid danger such as predators（食肉动物）.
The notion of an animal “sixth sense”一or14other mythical power一is an enduring one which the evidence on Sri Lanka's ravaged coast is likely to add15. 13._________
A.unwillingly
B.occasionally
C.doubtfully
D.certainly