當管(guan)底(di)為巖(yan)石、碎石或多石地(di)基時(shi)，對(dui)金屬管(guan)道(dao)應(ying)鋪(pu)(pu)墊(dian)不(bu)小于(yu)100 mm厚的中砂(sha)(sha)或粗(cu)砂(sha)(sha)，對(dui)非(fei)金屬管(guan)道(dao)應(ying)鋪(pu)(pu)墊(dian)不(bu)小于(yu)150 mm厚的中砂(sha)(sha)或粗(cu)砂(sha)(sha)，構成砂(sha)(sha)基礎(chu)，再(zai)在(zai)(zai)上面鋪(pu)(pu)設管(guan)道(dao)，如(ru)圖(tu)1.3.9(b)所示(shi)。當管(guan)底(di)地(di)基土(tu)(tu)(tu)質(zhi)松軟，承載力低(di)或鋪(pu)(pu)設大(da)管(guan)徑的鋼筋混(hun)凝(ning)(ning)(ning)土(tu)(tu)(tu)管(guan)道(dao)時(shi)，應(ying)采(cai)用混(hun)凝(ning)(ning)(ning)土(tu)(tu)(tu)基礎(chu)。根據地(di)基承載力的實際情況，可(ke)采(cai)用強度等級不(bu)低(di)于(yu)C10的混(hun)凝(ning)(ning)(ning)土(tu)(tu)(tu)帶形基礎(chu),也可(ke)采(cai)用混(hun)凝(ning)(ning)(ning)土(tu)(tu)(tu)枕基，如(ru)圖(tu)1.3.9 (c)所示(shi)。混(hun)凝(ning)(ning)(ning)土(tu)(tu)(tu)帶形基礎(chu)是沿管(guan)道(dao)全長(chang)做成的基礎(chu)，而混(hun)凝(ning)(ning)(ning)土(tu)(tu)(tu)枕基是只(zhi)在(zai)(zai)管(guan)道(dao)接(jie)口(kou)處用混(hun)凝(ning)(ning)(ning)土(tu)(tu)(tu)塊(kuai)墊(dian)起，其他地(di)方用中砂(sha)(sha)或粗(cu)砂(sha)(sha)填實。對(dui)混(hun)凝(ning)(ning)(ning)土(tu)(tu)(tu)基礎(chu)，如(ru)管(guan)道(dao)采(cai)用柔性接(jie)口(kou)，應(ying)每(mei)隔(ge)一(yi)定距離在(zai)(zai)柔性接(jie)口(kou)下，留出(chu)600~800mm的范圍不(bu)澆(jiao)筑混(hun)凝(ning)(ning)(ning)土(tu)(tu)(tu)，而

PP波(bo)(bo)(bo)紋(wen)(wen)(wen)管(guan) 象研究(jiu)梁的(de)(de)(de)變形一樣,我們從純彎(wan)(wan)曲的(de)(de)(de)情(qing)況著手,假(jia)設彎(wan)(wan)曲狀態(tai)下(xia)的(de)(de)(de)金屬波(bo)(bo)(bo)紋(wen)(wen)(wen)管(guan)的(de)(de)(de)軸(zhou)向剖面上取半(ban)(ban)個波(bo)(bo)(bo)峰(feng)寬度和半(ban)(ban)個波(bo)(bo)(bo)谷(gu)寬度作為微(wei)量(liang),從其通徑和波(bo)(bo)(bo)紋(wen)(wen)(wen)幾何形狀上去分析(見圖4-1)。常態(tai)下(xia)的(de)(de)(de)全屬波(bo)(bo)(bo)紋(wen)(wen)(wen)管(guan),AA、BB′、CC'、DD都是(shi)互相平行(xing)的(de)(de)(de)。PE波(bo)(bo)(bo)紋(wen)(wen)(wen)管(guan)彎(wan)(wan)曲之后(hou),軸(zhou)心線(xian)EG變成(cheng)了撓曲線(xian)。由(you)于撓曲線(xian)上方的(de)(de)(de)波(bo)(bo)(bo)谷(gu)的(de)(de)(de)半(ban)(ban)圓(yuan)弧所(suo)(suo)受拉應(ying)(ying)力(li)(li)與其下(xia)方波(bo)(bo)(bo)谷(gu)的(de)(de)(de)半(ban)(ban)圓(yuan)弧所(suo)(suo)受壓應(ying)(ying)力(li)(li)相等(deng),所(suo)(suo)以,BB依然(ran)平行(xing)于AA;由(you)于撓曲線(xian)上方的(de)(de)(de)波(bo)(bo)(bo)峰(feng)的(de)(de)(de)半(ban)(ban)圓(yuan)弧所(suo)(suo)受的(de)(de)(de)拉應(ying)(ying)力(li)(li)與其下(xia)方波(bo)(bo)(bo)峰(feng)的(de)(de)(de)半(ban)(ban)圓(yuan)弧所(suo)(suo)受的(de)(de)(de)壓應(ying)(ying)力(li)(li)相等(deng),以,DD'依然(ran)平行(xing)于CC

PP波紋(wen)管(guan)在(zai)橫向(xiang)(xiang)上受(shou)(shou)到力的(de)(de)作用之(zhi)(zhi)后,必然產生彎曲(qu)變形(xing),變形(xing)的(de)(de)主要部位就是圓(yuan)環膜(mo)片。凹(ao)面向(xiang)(xiang)心(xin)(xin)和(he)(he)凹(ao)面背(bei)心(xin)(xin)的(de)(de)兩個(ge)半(ban)圓(yuan)弧從軸(zhou)向(xiang)(xiang)剖面圖上來看,它稱(cheng)作波峰和(he)(he)波谷)剛性(xing)大,它與圓(yuan)環膜(mo)片相比,變形(xing)極小(xiao)。也就是說(shuo),凹(ao)面向(xiang)(xiang)心(xin)(xin)和(he)(he)凹(ao)面背(bei)心(xin)(xin)的(de)(de)半(ban)圓(yuan)弧的(de)(de)小(xiao)半(ban)徑以(yi)及(ji)連接它們(men)的(de)(de)圓(yuan)環膜(mo)片的(de)(de)內、外半(ban)徑差,這兩個(ge)參數與變形(xing)有著直(zhi)接的(de)(de)關系。但由于(yu)制造工藝上的(de)(de)困難,一定(ding)通(tong)徑的(de)(de)PE波紋(wen)管(guan)的(de)(de)波紋(wen)高度將受(shou)(shou)到其最大值(zhi)(zhi)的(de)(de)限制。這就是說(shuo),波峰和(he)(he)波谷半(ban)圓(yuan)弧的(de)(de)小(xiao)半(ban)徑及(ji)圓(yuan)環膜(mo)片的(de)(de)內、外半(ban)徑之(zhi)(zhi)差這兩個(ge)值(zhi)(zhi)的(de)(de)確定(ding),是以(yi)通(tong)徑大小(xiao)為基(ji)礎的(de)(de)。從這個(ge)意義上來看,通(tong)徑大小(xiao)是影響金屬波紋(wen)管(guan)變形(xing)的(de)(de)主要因(yin)素(su)。

PP波(bo)(bo)(bo)(bo)紋(wen)管以圓(yuan)片(pian)(pian)(pian)(pian)翹曲(qu)理論(lun)為(wei)基礎確定(ding)波(bo)(bo)(bo)(bo)紋(wen)管的(de)縱向剛度金(jin)屬(shu)波(bo)(bo)(bo)(bo)紋(wen)管的(de)結構特點(dian)說(shuo)明了它在(zai)受到軸向力的(de)作用之后,各(ge)部(bu)分(fen)很(hen)容易(yi)產生彈(dan)性(xing)變形(xing)。PE波(bo)(bo)(bo)(bo)紋(wen)管由于(yu)波(bo)(bo)(bo)(bo)峰半(ban)(ban)圓(yuan)弧(hu)和波(bo)(bo)(bo)(bo)谷半(ban)(ban)圓(yuan)弧(hu)這(zhe)兩部(bu)分(fen)的(de)相對變形(xing)遠遠小于(yu)圓(yuan)環膜(mo)片(pian)(pian)(pian)(pian)部(bu)分(fen)因(yin)此,可以忽(hu)略不計,并(bing)把它們視為(wei)圓(yuan)環膜(mo)片(pian)(pian)(pian)(pian)與圓(yuan)環膜(mo)片(pian)(pian)(pian)(pian)之間的(de)剛性(xing)接(jie)點(dian)。把波(bo)(bo)(bo)(bo)紋(wen)管復雜的(de)受力狀態簡化為(wei)圓(yuan)環膜(mo)片(pian)(pian)(pian)(pian)單一受力的(de)形(xing)式。這(zhe)樣(yang),便(bian)可以用圖片(pian)(pian)(pian)(pian)翹曲(qu)理論(lun)為(wei)基礎去(qu)分(fen)析整個(ge)波(bo)(bo)(bo)(bo)紋(wen)管的(de)縱向剛度

PE波(bo)紋管(guan)(guan)給(gei)水管(guan)(guan)道的(de)基(ji)礎用(yong)來防止管(guan)(guan)道不均勻沉(chen)陷造成管(guan)(guan)道破裂或(huo)接口損(sun)壞(huai)而(er)漏水。般情(qing)況下有(you)三(san)種基(ji)礎。當管(guan)(guan)底(di)地(di)基(ji)土層承載力較高(gao)，地(di)下水位較低(di)時，可(ke)采用(yong)天然地(di)基(ji)作為PP波(bo)紋管(guan)(guan)管(guan)(guan)道基(ji)礎。施(shi)工(gong)時，將天然地(di)基(ji)整平，管(guan)(guan)道鋪(pu)設(she)在(zai)未經擾(rao)動的(de)原狀土上即可(ke)，如圖1.3.9(a) 所示。為安全起(qi)見，可(ke)將天然地(di)基(ji)夯實(shi)后(hou)再鋪(pu)設(she)管(guan)(guan)道;為保證管(guan)(guan)道鋪(pu)設(she)的(de)位置(zhi)正確，可(ke)將槽(cao)(cao)底(di)做成90°~ 135*的(de)弧形(xing)槽(cao)(cao)。