實驗名稱：含鹽人工凍土的聲學(xue)特性(xing)研(yan)究

　　研究方向：人(ren)工(gong)(gong)(gong)凍(dong)(dong)(dong)(dong)結(jie)(jie)法(fa)(fa)是利用(yong)人(ren)工(gong)(gong)(gong)制冷技術使地層中(zhong)的(de)(de)水結(jie)(jie)冰形成(cheng)凍(dong)(dong)(dong)(dong)土，隔絕地下(xia)(xia)水與地下(xia)(xia)工(gong)(gong)(gong)程(cheng)的(de)(de)聯系，在凍(dong)(dong)(dong)(dong)結(jie)(jie)壁的(de)(de)保護下(xia)(xia)進行(xing)地下(xia)(xia)工(gong)(gong)(gong)程(cheng)施工(gong)(gong)(gong)。通常采用(yong)凍(dong)(dong)(dong)(dong)結(jie)(jie)管中(zhong)循環低溫(wen)冷媒劑（凍(dong)(dong)(dong)(dong)結(jie)(jie)法(fa)(fa)施工(gong)(gong)(gong)中(zhong)多用(yong)氯化鈣溶液作冷媒劑）的(de)(de)方(fang)式把天(tian)然(ran)巖(yan)土變(bian)成(cheng)人(ren)工(gong)(gong)(gong)凍(dong)(dong)(dong)(dong)土，然(ran)而受地層條(tiao)件、凍(dong)(dong)(dong)(dong)結(jie)(jie)孔偏斜、凍(dong)(dong)(dong)(dong)結(jie)(jie)工(gong)(gong)(gong)藝及掘砌方(fang)式影響，凍(dong)(dong)(dong)(dong)結(jie)(jie)管斷裂事故時有(you)發(fa)生(sheng)，導(dao)致的(de)(de)鹽(yan)(yan)水泄漏問題，不(bu)(bu)(bu)利于凍(dong)(dong)(dong)(dong)結(jie)(jie)壁穩定。目前凍(dong)(dong)(dong)(dong)結(jie)(jie)壁發(fa)育狀(zhuang)況評估方(fang)法(fa)(fa)有(you)圖乘法(fa)(fa)、經驗公式法(fa)(fa)、數值模(mo)擬法(fa)(fa)等(deng)，這三(san)種方(fang)法(fa)(fa)存(cun)在的(de)(de)缺(que)點是對測溫(wen)孔內測溫(wen)結(jie)(jie)果(guo)的(de)(de)依賴程(cheng)度(du)高，在距測溫(wen)孔較遠時判斷不(bu)(bu)(bu)準確，容易忽略局部凍(dong)(dong)(dong)(dong)結(jie)(jie)壁開窗、強度(du)不(bu)(bu)(bu)足(zu)等(deng)關鍵信息。而對于含鹽(yan)(yan)條(tiao)件下(xia)(xia)的(de)(de)人(ren)工(gong)(gong)(gong)地層凍(dong)(dong)(dong)(dong)結(jie)(jie)，溫(wen)度(du)場變(bian)化受鹽(yan)(yan)分的(de)(de)影響情況復雜，通過(guo)現有(you)檢測手段對異常情況的(de)(de)探測更加困(kun)難。例如當鹽(yan)(yan)分分布(bu)不(bu)(bu)(bu)均，凍(dong)(dong)(dong)(dong)結(jie)(jie)壁形成(cheng)形狀(zhuang)可(ke)能不(bu)(bu)(bu)規(gui)則(ze)，或因鹽(yan)(yan)水泄露存(cun)在不(bu)(bu)(bu)確定的(de)(de)開窗風險。針(zhen)對含鹽(yan)(yan)的(de)(de)特殊凍(dong)(dong)(dong)(dong)結(jie)(jie)條(tiao)件，了解凍(dong)(dong)(dong)(dong)結(jie)(jie)壁的(de)(de)發(fa)育狀(zhuang)況和工(gong)(gong)(gong)程(cheng)性(xing)能對于人(ren)工(gong)(gong)(gong)凍(dong)(dong)(dong)(dong)結(jie)(jie)法(fa)(fa)安全(quan)施工(gong)(gong)(gong)十(shi)分重要。

　　聲(sheng)(sheng)波在(zai)巖(yan)土(tu)(tu)介質(zhi)中(zhong)傳播，其(qi)(qi)聲(sheng)(sheng)學(xue)特性(xing)與(yu)巖(yan)土(tu)(tu)物(wu)理(li)力(li)學(xue)性(xing)質(zhi)密切(qie)相關。在(zai)人(ren)工(gong)地層凍(dong)(dong)結(jie)工(gong)程中(zhong)認識(shi)含鹽人(ren)工(gong)凍(dong)(dong)土(tu)(tu)的(de)聲(sheng)(sheng)學(xue)特性(xing)，建立聲(sheng)(sheng)波參數與(yu)含鹽人(ren)工(gong)凍(dong)(dong)土(tu)(tu)物(wu)理(li)力(li)學(xue)性(xing)質(zhi)的(de)關系，可為(wei)聲(sheng)(sheng)波探測(ce)鹽水浸漬(zi)凍(dong)(dong)結(jie)壁異常情(qing)況提供必(bi)要依據(ju)。聲(sheng)(sheng)波檢(jian)測(ce)作為(wei)一(yi)種方便快捷的(de)無損檢(jian)測(ce)技術有(you)望實現這一(yi)目標。聲(sheng)(sheng)波在(zai)凍(dong)(dong)土(tu)(tu)中(zhong)傳播時(shi)，其(qi)(qi)聲(sheng)(sheng)波特性(xing)是凍(dong)(dong)土(tu)(tu)溫度、含水量、密度、凍(dong)(dong)土(tu)(tu)中(zhong)裂隙情(qing)況、應力(li)狀態(tai)等因(yin)素(su)的(de)綜合(he)指標，同(tong)時(shi)凍(dong)(dong)土(tu)(tu)強度也是這些因(yin)素(su)的(de)綜合(he)反映，通過二者之間(jian)的(de)關系，可實現現場快速測(ce)定凍(dong)(dong)土(tu)(tu)聲(sheng)(sheng)參數從(cong)而對原位現場凍(dong)(dong)土(tu)(tu)力(li)學(xue)性(xing)質(zhi)進行推算。

　　實驗目的：驗證含鹽人工(gong)凍土的聲學(xue)特性

　　測試設備：信號發生器(qi)、ATA-2022H高壓放大器(qi)、示波器(qi)、電(dian)荷放大器(qi)、壓電(dian)陶瓷傳(chuan)感器(qi)等。

　　實(shi)驗過(guo)程：首先由(you)(you)函數(shu)(shu)發生(sheng)器(qi)激(ji)發單周期正(zheng)弦(xian)波(bo)(bo)(bo)，然后(hou)(hou)激(ji)發信號經由(you)(you)ATA-2022H高壓(ya)放(fang)大(da)(da)器(qi)放(fang)大(da)(da)后(hou)(hou)分兩路，一(yi)(yi)(yi)路直接(jie)輸出到數(shu)(shu)字示波(bo)(bo)(bo)器(qi)作(zuo)為(wei)激(ji)發波(bo)(bo)(bo)形(xing)信號，另(ling)一(yi)(yi)(yi)路用于驅動壓(ya)電陶瓷傳(chuan)(chuan)感器(qi)產生(sheng)振動激(ji)發聲波(bo)(bo)(bo)，聲波(bo)(bo)(bo)通過(guo)測試試樣傳(chuan)(chuan)播，另(ling)一(yi)(yi)(yi)端由(you)(you)壓(ya)電陶瓷接(jie)收(shou)傳(chuan)(chuan)感器(qi)收(shou)到信號后(hou)(hou)，再經由(you)(you)電荷放(fang)大(da)(da)器(qi)對信號濾波(bo)(bo)(bo)后(hou)(hou)再次放(fang)大(da)(da)傳(chuan)(chuan)輸到數(shu)(shu)字示波(bo)(bo)(bo)器(qi)作(zuo)為(wei)接(jie)收(shou)波(bo)(bo)(bo)形(xing)信號，最(zui)后(hou)(hou)利(li)用示波(bo)(bo)(bo)器(qi)的(de)存(cun)儲(chu)功能(neng)將(jiang)波(bo)(bo)(bo)形(xing)數(shu)(shu)據導入到計(ji)算機(ji)中進(jin)行傳(chuan)(chuan)播時(shi)間的(de)確定，實(shi)驗系統搭建如圖1-1。

　　圖(tu)1-1實(shi)驗系統圖(tu)

　　實驗結果：

　　圖1-2波速比(bi)變(bian)化規律圖

　　圖(tu)1-2(a)中可以(yi)發(fa)現無(wu)(wu)圍(wei)(wei)(wei)壓條(tiao)件下(xia)，波(bo)(bo)(bo)速(su)比(bi)隨含(han)鹽量(liang)增(zeng)(zeng)加(jia)略有減少，變化范(fan)圍(wei)(wei)(wei)為1.82~2.41，由此可見(jian)(jian)，無(wu)(wu)圍(wei)(wei)(wei)壓作用時(shi)，波(bo)(bo)(bo)速(su)比(bi)對含(han)鹽量(liang)的變化不敏感，凍土在(zai)完全飽(bao)和時(shi)的波(bo)(bo)(bo)速(su)比(bi)要大于未飽(bao)和時(shi)的波(bo)(bo)(bo)速(su)比(bi)，可見(jian)(jian)波(bo)(bo)(bo)速(su)比(bi)不僅與土質有關，還與飽(bao)和度有關，在(zai)低圍(wei)(wei)(wei)壓條(tiao)件下(xia)（4MPa、6MPa）波(bo)(bo)(bo)速(su)比(bi)隨含(han)鹽量(liang)的增(zeng)(zeng)加(jia)而增(zeng)(zeng)大；高圍(wei)(wei)(wei)壓條(tiao)件下(xia)（8MPa），波(bo)(bo)(bo)速(su)比(bi)隨含(han)鹽量(liang)的增(zeng)(zeng)加(jia)而減小。圖(tu)1-2(b)中可以(yi)發(fa)現，相同含(han)鹽量(liang)凍結(jie)粉砂的波(bo)(bo)(bo)速(su)比(bi)整體上隨著(zhu)圍(wei)(wei)(wei)壓的增(zeng)(zeng)大而增(zeng)(zeng)大。

　　功率放(fang)大器推(tui)薦(jian)：ATA-2022B高壓放(fang)大器

　　圖：ATA-2022B高壓放大器指標參數

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