工作基點和觀測點標志的布設

  工(gong)作基(ji)(ji)點(dian)(dian)(dian)(dian)(dian)(以(yi)下簡稱基(ji)(ji)點(dian)(dian)(dian)(dian)(dian))是(shi)沉降觀測的(de)(de)(de)(de)基(ji)(ji)準點(dian)(dian)(dian)(dian)(dian)，應根據工(gong)程的(de)(de)(de)(de)沉降施(shi)測方(fang)案(an)和(he)布(bu)網原則的(de)(de)(de)(de)要(yao)(yao)求建立，而沉降施(shi)測方(fang)案(an)應根據工(gong)程的(de)(de)(de)(de)布(bu)局特點(dian)(dian)(dian)(dian)(dian)、現場的(de)(de)(de)(de)環境條(tiao)(tiao)件(jian)(jian)制訂。依據工(gong)作經驗，一般高層(ceng)建筑物(wu)周(zhou)圍要(yao)(yao)布(bu)設三個基(ji)(ji)點(dian)(dian)(dian)(dian)(dian)，且與(yu)建筑物(wu)相距(ju)50m至(zhi)100m間(jian)的(de)(de)(de)(de)范(fan)圍為宜(yi)。基(ji)(ji)點(dian)(dian)(dian)(dian)(dian)可(ke)利(li)用(yong)已有的(de)(de)(de)(de)、穩(wen)(wen)定(ding)(ding)(ding)性(xing)好的(de)(de)(de)(de)埋石(shi)點(dian)(dian)(dian)(dian)(dian)和(he)墻腳水準點(dian)(dian)(dian)(dian)(dian)，也可(ke)以(yi)在該區(qu)域內(nei)基(ji)(ji)礎(chu)穩(wen)(wen)定(ding)(ding)(ding)、修建時間(jian)長的(de)(de)(de)(de)建筑物(wu)上設置墻腳水準點(dian)(dian)(dian)(dian)(dian)。若(ruo)區(qu)域內(nei)不具備上述條(tiao)(tiao)件(jian)(jian)，則可(ke)按(an)相應要(yao)(yao)求，選在隱蔽性(xing)好且通視良好、確保地(di)方(fang)埋設基(ji)(ji)點(dian)(dian)(dian)(dian)(dian)。所布(bu)設的(de)(de)(de)(de)基(ji)(ji)點(dian)(dian)(dian)(dian)(dian)，在未確定(ding)(ding)(ding)其穩(wen)(wen)定(ding)(ding)(ding)性(xing)前，嚴禁使(shi)用(yong)。因此(ci)，每(mei)次都(dou)要(yao)(yao)測定(ding)(ding)(ding)基(ji)(ji)點(dian)(dian)(dian)(dian)(dian)間(jian)的(de)(de)(de)(de)高差，以(yi)判定(ding)(ding)(ding)它(ta)們之間(jian)是(shi)否相對穩(wen)(wen)定(ding)(ding)(ding)，并(bing)且基(ji)(ji)點(dian)(dian)(dian)(dian)(dian)要(yao)(yao)定(ding)(ding)(ding)期與(yu)遠離建筑物(wu)的(de)(de)(de)(de)高等(deng)級水準點(dian)(dian)(dian)(dian)(dian)聯測，以(yi)檢核其本身的(de)(de)(de)(de)穩(wen)(wen)定(ding)(ding)(ding)性(xing)。

  沉(chen)降(jiang)觀測點(dian)(dian)應(ying)依據建(jian)(jian)(jian)筑(zhu)(zhu)物(wu)的(de)(de)形(xing)狀、結構、地(di)(di)質(zhi)(zhi)條件(jian)、樁形(xing)等(deng)因素綜合(he)考慮(lv)，布(bu)設(she)在能(neng)(neng)敏感反(fan)映(ying)建(jian)(jian)(jian)筑(zhu)(zhu)物(wu)沉(chen)降(jiang)變化的(de)(de)地(di)(di)點(dian)(dian)。一般布(bu)設(she)在建(jian)(jian)(jian)筑(zhu)(zhu)物(wu)四角(jiao)、差異沉(chen)降(jiang)量大(da)的(de)(de)位(wei)置、地(di)(di)質(zhi)(zhi)條件(jian)有明顯不同的(de)(de)區段以及(ji)沉(chen)降(jiang)裂縫的(de)(de)兩側。埋(mai)設(she)時注意觀測點(dian)(dian)與(yu)建(jian)(jian)(jian)筑(zhu)(zhu)物(wu)的(de)(de)聯結要牢靠，使得觀測點(dian)(dian)的(de)(de)變化能(neng)(neng)真正反(fan)映(ying)建(jian)(jian)(jian)筑(zhu)(zhu)物(wu)的(de)(de)變化情況。并(bing)根據建(jian)(jian)(jian)筑(zhu)(zhu)物(wu)的(de)(de)平面(mian)設(she)計圖(tu)紙繪制沉(chen)降(jiang)觀測點(dian)(dian)布(bu)點(dian)(dian)圖(tu)，以確定沉(chen)降(jiang)觀測點(dian)(dian)的(de)(de)位(wei)置。在工(gong)作(zuo)點(dian)(dian)與(yu)沉(chen)降(jiang)觀測點(dian)(dian)之間要建(jian)(jian)(jian)立固定的(de)(de)觀測路線，并(bing)在架設(she)儀器站點(dian)(dian)與(yu)轉點(dian)(dian)處做好標記(ji)樁，保證各(ge)次觀測均沿統(tong)一路線。

  沉降觀測的周期及施測過程

  沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)的(de)(de)(de)周(zhou)(zhou)(zhou)期(qi)(qi)(qi)應(ying)能反映出建(jian)(jian)(jian)(jian)筑(zhu)(zhu)(zhu)物(wu)(wu)的(de)(de)(de)沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)變形規(gui)律(lv)，建(jian)(jian)(jian)(jian)(構)筑(zhu)(zhu)(zhu)物(wu)(wu)的(de)(de)(de)沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)對(dui)(dui)時(shi)(shi)(shi)間(jian)有(you)(you)(you)嚴格的(de)(de)(de)限(xian)制條(tiao)件，特別是(shi)(shi)(shi)觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)按時(shi)(shi)(shi)進行(xing)，否(fou)則沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)得(de)不(bu)(bu)到原(yuan)始(shi)數(shu)據(ju)，從而(er)使整(zheng)個(ge)觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)得(de)不(bu)(bu)到完整(zheng)的(de)(de)(de)觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)結果。其(qi)他各(ge)(ge)階段的(de)(de)(de)復測(ce)(ce)(ce)(ce)，根據(ju)工(gong)(gong)(gong)(gong)(gong)程(cheng)(cheng)進展(zhan)情況必(bi)須定(ding)(ding)時(shi)(shi)(shi)進行(xing)，不(bu)(bu)得(de)漏測(ce)(ce)(ce)(ce)或補測(ce)(ce)(ce)(ce)，只有(you)(you)(you)這樣，才能得(de)到準(zhun)確(que)(que)(que)的(de)(de)(de)沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)情況或規(gui)律(lv)。一(yi)(yi)(yi)般(ban)(ban)認為建(jian)(jian)(jian)(jian)筑(zhu)(zhu)(zhu)在(zai)(zai)(zai)砂(sha)類土層上的(de)(de)(de)建(jian)(jian)(jian)(jian)筑(zhu)(zhu)(zhu)物(wu)(wu)，其(qi)沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)在(zai)(zai)(zai)施工(gong)(gong)(gong)(gong)(gong)期(qi)(qi)(qi)間(jian)已(yi)大(da)部(bu)分完成，而(er)建(jian)(jian)(jian)(jian)筑(zhu)(zhu)(zhu)在(zai)(zai)(zai)粘土類土層上的(de)(de)(de)建(jian)(jian)(jian)(jian)筑(zhu)(zhu)(zhu)物(wu)(wu)，其(qi)沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)在(zai)(zai)(zai)施工(gong)(gong)(gong)(gong)(gong)期(qi)(qi)(qi)間(jian)只是(shi)(shi)(shi)整(zheng)個(ge)沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)量(liang)(liang)的(de)(de)(de)一(yi)(yi)(yi)部(bu)分，因而(er)，沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)周(zhou)(zhou)(zhou)期(qi)(qi)(qi)是(shi)(shi)(shi)變化(hua)的(de)(de)(de)。根據(ju)工(gong)(gong)(gong)(gong)(gong)作經驗，在(zai)(zai)(zai)施工(gong)(gong)(gong)(gong)(gong)階段，觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)的(de)(de)(de)頻率要大(da)些，一(yi)(yi)(yi)般(ban)(ban)按3天(tian)、7天(tian)、15天(tian)確(que)(que)(que)定(ding)(ding)觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)周(zhou)(zhou)(zhou)期(qi)(qi)(qi)，或按層數(shu)、荷載的(de)(de)(de)增(zeng)加(jia)確(que)(que)(que)定(ding)(ding)觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)周(zhou)(zhou)(zhou)期(qi)(qi)(qi)，觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)周(zhou)(zhou)(zhou)期(qi)(qi)(qi)具(ju)體應(ying)視施工(gong)(gong)(gong)(gong)(gong)過程(cheng)(cheng)中地基(ji)(ji)與(yu)(yu)加(jia)荷而(er)定(ding)(ding)。如(ru)暫時(shi)(shi)(shi)停工(gong)(gong)(gong)(gong)(gong)時(shi)(shi)(shi)，在(zai)(zai)(zai)停工(gong)(gong)(gong)(gong)(gong)時(shi)(shi)(shi)和(he)重新開工(gong)(gong)(gong)(gong)(gong)時(shi)(shi)(shi)均應(ying)各(ge)(ge)觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)一(yi)(yi)(yi)次，以(yi)便(bian)檢驗停工(gong)(gong)(gong)(gong)(gong)期(qi)(qi)(qi)間(jian)建(jian)(jian)(jian)(jian)筑(zhu)(zhu)(zhu)物(wu)(wu)沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)變化(hua)情況，為重新開工(gong)(gong)(gong)(gong)(gong)后(hou)(hou)沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)的(de)(de)(de)方(fang)式(shi)、次數(shu)是(shi)(shi)(shi)否(fou)應(ying)調(diao)整(zheng)作判斷依據(ju)。在(zai)(zai)(zai)竣(jun)工(gong)(gong)(gong)(gong)(gong)后(hou)(hou)，觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)的(de)(de)(de)頻率可以(yi)少些，視地基(ji)(ji)土類型和(he)沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)速度的(de)(de)(de)大(da)小(xiao)而(er)定(ding)(ding)，一(yi)(yi)(yi)般(ban)(ban)有(you)(you)(you)一(yi)(yi)(yi)個(ge)月(yue)、兩個(ge)月(yue)、三個(ge)月(yue)、半年與(yu)(yu)一(yi)(yi)(yi)年等不(bu)(bu)同周(zhou)(zhou)(zhou)期(qi)(qi)(qi)。沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)是(shi)(shi)(shi)否(fou)進入穩(wen)定(ding)(ding)階段，應(ying)由沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)量(liang)(liang)與(yu)(yu)時(shi)(shi)(shi)間(jian)關系曲(qu)線判定(ding)(ding)。對(dui)(dui)重點觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)和(he)科研項目工(gong)(gong)(gong)(gong)(gong)程(cheng)(cheng)，若三個(ge)周(zhou)(zhou)(zhou)期(qi)(qi)(qi)觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)中每周(zhou)(zhou)(zhou)期(qi)(qi)(qi)的(de)(de)(de)沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)量(liang)(liang)不(bu)(bu)大(da)于2倍的(de)(de)(de)測(ce)(ce)(ce)(ce)量(liang)(liang)中誤(wu)差，可認為已(yi)進入穩(wen)定(ding)(ding)階段。一(yi)(yi)(yi)般(ban)(ban)工(gong)(gong)(gong)(gong)(gong)程(cheng)(cheng)的(de)(de)(de)沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)觀(guan)(guan)(guan)(guan)測(ce)(ce)(ce)(ce)，若沉(chen)(chen)降(jiang)(jiang)(jiang)(jiang)(jiang)速度小(xiao)于0.01～0.04mm/d，可認為進入穩(wen)定(ding)(ding)階段，具(ju)體取值應(ying)根據(ju)各(ge)(ge)地區地基(ji)(ji)土的(de)(de)(de)壓(ya)縮性確(que)(que)(que)定(ding)(ding)。

  根據(ju)編制的(de)(de)沉(chen)降施(shi)測(ce)(ce)(ce)(ce)(ce)(ce)方案及(ji)確定的(de)(de)觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)周期，觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)應(ying)在觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)點(dian)(dian)穩(wen)固(gu)后及(ji)時進行。一(yi)般(ban)高(gao)(gao)層建筑物有一(yi)層或數(shu)層地下結構(gou)，觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)應(ying)自(zi)基(ji)礎開始，在基(ji)礎的(de)(de)縱橫軸(zhou)線上(基(ji)礎局(ju)邊)按設計(ji)好的(de)(de)位置埋設沉(chen)降觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)點(dian)(dian)(臨(lin)時的(de)(de))，待臨(lin)時觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)點(dian)(dian)穩(wen)固(gu)好，方可(ke)進行觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)。觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)的(de)(de)沉(chen)降觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)點(dian)(dian)高(gao)(gao)程值是(shi)以后各次觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)用以比較(jiao)的(de)(de)基(ji)礎，其(qi)精(jing)度(du)要(yao)求非常高(gao)(gao)，施(shi)測(ce)(ce)(ce)(ce)(ce)(ce)時一(yi)般(ban)用N2級精(jing)密(mi)水準儀，并且要(yao)求每個(ge)觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)點(dian)(dian)高(gao)(gao)程應(ying)在同期觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)兩次，比較(jiao)觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)結果，若同一(yi)觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)點(dian)(dian)間(jian)的(de)(de)高(gao)(gao)差不超過±0.5mm時，我們即(ji)可(ke)認為觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)的(de)(de)數(shu)據(ju)是(shi)可(ke)靠的(de)(de)。隨著結構(gou)每升高(gao)(gao)一(yi)層，臨(lin)時觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)點(dian)(dian)移上一(yi)層并進行觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)，直到+0.00再按規定埋設觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)點(dian)(dian)(為便于觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)可(ke)將(jiang)觀(guan)測(ce)(ce)(ce)(ce)(ce)(ce)點(dian)(dian)設于+500mm)，然后每施(shi)工一(yi)層就復測(ce)(ce)(ce)(ce)(ce)(ce)一(yi)次，直至(zhi)竣工。

  在施(shi)工打樁、基(ji)坑(keng)開挖以及基(ji)礎完工后(hou)，上部不(bu)斷加(jia)層的(de)階段進(jin)行沉(chen)降(jiang)觀(guan)測(ce)時(shi)，記載(zai)每(mei)次(ci)觀(guan)測(ce)的(de)施(shi)工進(jin)度、增加(jia)荷載(zai)量、倉庫進(jin)(出(chu))貨噸位、建筑物傾斜裂縫(feng)等各種影響沉(chen)降(jiang)變化和(he)(he)異(yi)常的(de)情(qing)況。每(mei)周觀(guan)測(ce)后(hou)，應及時(shi)對觀(guan)測(ce)資料進(jin)行整理，計算出(chu)觀(guan)測(ce)點的(de)沉(chen)降(jiang)量、沉(chen)降(jiang)差以及本周期平均沉(chen)降(jiang)量和(he)(he)沉(chen)降(jiang)速度。若出(chu)現(xian)變化量異(yi)常時(shi)，應立即通知委托方(fang)，為其采取防患措(cuo)施(shi)提供依據，同時(shi)適當增加(jia)觀(guan)測(ce)次(ci)數。

  另(ling)者，不同周期的(de)(de)(de)觀(guan)(guan)(guan)測(ce)應遵循“五(wu)定(ding)(ding)”原(yuan)則。所謂(wei)“五(wu)定(ding)(ding)”，即通常所說的(de)(de)(de)沉降(jiang)觀(guan)(guan)(guan)測(ce)依據的(de)(de)(de)基準(zhun)點、基點和(he)被(bei)觀(guan)(guan)(guan)測(ce)物上沉降(jiang)觀(guan)(guan)(guan)測(ce)點，點位要穩(wen)定(ding)(ding);所用(yong)儀器、設備要穩(wen)定(ding)(ding);觀(guan)(guan)(guan)測(ce)人員要穩(wen)定(ding)(ding);觀(guan)(guan)(guan)測(ce)時的(de)(de)(de)環境條件基本上要一致;觀(guan)(guan)(guan)測(ce)路(lu)線、鏡(jing)位、程序和(he)方法(fa)要固定(ding)(ding)。以上措施在客觀(guan)(guan)(guan)上能保(bao)證(zheng)盡(jin)量(liang)減少觀(guan)(guan)(guan)測(ce)誤差(cha)的(de)(de)(de)主觀(guan)(guan)(guan)不確(que)定(ding)(ding)性，使(shi)所測(ce)的(de)(de)(de)結(jie)果(guo)具(ju)有統一的(de)(de)(de)趨向性;能保(bao)證(zheng)各次復測(ce)結(jie)果(guo)與觀(guan)(guan)(guan)測(ce)結(jie)果(guo)的(de)(de)(de)可(ke)比(bi)性一致，使(shi)所觀(guan)(guan)(guan)測(ce)的(de)(de)(de)沉降(jiang)量(liang)更真實。