normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24.1pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>一、前言
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>在高速公路建設中,普遍存在一個問題:路面在臺背回填處出現不同程度的沉降斷裂,據資料顯示,最大的沉降值達到
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24.1pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>二、工程實例
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>青銀高速公路是我國高速公路路網“五縱七橫”規劃中的重要組成部分,其K105+033處l一
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24.1pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>三、橋頭跳車對行車速度的影響
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>由于橋臺臺背沉陷、斷裂而形成的臺階,會使車輛的行駛速度受到不同程度的影響。車速的降低幅度與臺階高度、路面類型、道路等級、車輛類型和行駛速度等多種因素有關。根據實地觀察和有關資料調查表明,當橋頭臺階達
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24.1pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>四、橋頭跳車原因分析
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>1.原地基土質不良
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>道路原地表為軟土路段,土質較差,容易產生較大地基沉降。由于軟土一般都具有天然含水量高、孔隙比大、壓縮性強和抗剪強度低等特點,在軟土上填筑路基,極易產生沉降(包括瞬時沉降、固結沉降和次固結沉降)。 同時,橋頭路基填筑高度較其它地段大,產生基底應力相對較大,更易引起地基沉降,特別是工后沉降較大。
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>2.基坑回填范圍小,大型壓實機械不能使用
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>一般橋梁的橋臺基坑都相對狹小,不易于使用目前較先進的大型壓實機械進行碾壓,而且大噸位機械振動力太大時,對橋臺有影響。因此在橋臺基坑的壓實中,往往只能使用小型壓實機具,甚至于只能人工夯實,使得回填土不易壓實。
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>3.填料自身容易產生壓縮變形
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>與橋臺相接的道路路基填方較高,路基填料因含水分,易產生壓縮變形,施工中采取任何措施也難將填料顆粒問的孔隙完全消除,在道路自重及車輛的垂直荷載與振動荷載作用下,孔隙率逐漸降低,填料逐漸壓縮,密實度逐漸增大,在一定期限內路基產生沉降。因此,壓縮沉降主要取決于填料自身的性質、施工條件及臺前臺背的防護排水工程設置等情況。根據有關資料調查研究:當土堤壓實度為95%時,每米填土工后的沉降約為
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>4.剛性結構與柔性路面過渡界限太明顯
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>由于橋臺一般采用剛性很大的堅石砌筑或鋼筋混凝土澆注而成,具有較大的整體剛度,屬剛性體,而與橋臺相連的道路,通常采用柔性較大瀝青混凝土路面,屬彈塑性體。顯然,道路與橋臺之問存在著較大的剛度差,這個剛度差的存在必然引起道路與橋臺之間產生較大的塑性變形相對差和較大的剛度突變,其過渡界限又太明顯,這樣勢必增強橋頭跳車的振動效果。
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>5.路基排水及防滲系統不完善
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>路基排水及防滲系統不完善,長期受到雨水的侵蝕,從而引起路面的豎向變形,產生橋頭跳車。
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24.1pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>五、原材料及配合比
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>針對產生橋頭跳車原因分析結果,本工程中決定采用輕質高強的原材料進行基坑回填及臺背回填,所用原材料及試驗結果如下:
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>1.原材料試驗
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>(1)水泥:采用河北臨城p032.5R水泥,其技術性能指標見表1。
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 18.05pt; LINE-HEIGHT: 200%; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=center>表1 水泥技術性能指標
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>指標 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>初凝時間(b:min) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>終凝時間(b:min) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>安定性 (雷式法) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>28d抗折強度 (MPa) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>28d抗壓強度(MPa) |
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>水泥 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>2:22 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>3:27 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>0.8 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>7.1 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>46.3 |
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>(2)粉煤灰:采用石家莊欒城熱電廠的濕 排粉煤灰,其技術性能指標見表2。
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 18.05pt; LINE-HEIGHT: 200%; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=center>表2 粉煤灰技術性能指標
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>指標 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>比表面積(cm3/g) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>燒失量(%) | normal style="MARGIN: 0cm 0cm 0pt 4.5pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>二氧化硅 含量(%) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>三氧化二鋁含量(%) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>三氧化二鐵(%) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>氧化鈣含量(%) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>氧化鎂含量(%) |
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>粉煤灰 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>31.29 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>9.39 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>47.23 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>29.22 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>3.32 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>3.74 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>0.95 |
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>(3)石灰:采用隆堯產生石灰,其有效氧化鈣與氧化鎂含量為75.6%,滿足III級以上生石灰要求,并且要求消解以后過
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>(4)減水劑:采用河北省混凝土外加劑廠生產的DH
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 18.05pt; LINE-HEIGHT: 200%; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=center>表3 減水劑技術性能指標
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>指標名稱 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>減水率(%) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>泌水率比(%) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>含水量(%) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>凝結時間差 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>抗壓強度比(%) | |||
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>初凝 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>終凝 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>R1 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>R3 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>R7 | ||||
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>減水劑 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>20 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>63 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>2.0 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>-60 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>-55 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>176 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>154 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>142 |
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left> (5)高塑性粘土:采用塑性指數大于8的粘性土,作為石灰土及包邊土的原材料。經過沿線試驗分析比較,決定采用孟村2號土場的粘性土,其塑性指數為8.2,塑限為24.5%,液限為32.4%,滿足施工指導書要求。
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>2.配合比組成設計
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>針對產生橋頭跳車的原因分析結果,對原材料進行了多種組成設計,如免于碾壓的流態粉煤灰、自重較小的二灰、高強的石灰土碎石等,其配合比設計結果如下:
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>(1)基坑回填采用流態粉煤灰,其配合比組成為:水泥-粉煤灰-水-減水劑(質量比)=6:94:65:0.06,其7d抗壓強度為0.442MPa,28d抗壓強度為0.690MPa,滿足技術規范要求。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>(2)封層采用8%石灰土。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>(3)石灰粉煤灰為臺背主要填方材料I其配合比組成為:石灰:粉煤灰(質量比):= 8:100,其7d無側限抗壓強度為0.86MPa,滿足技術規范要求。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>(4)搭板下30em范圍采用石灰土碎石,其配合比組成為:8%石灰土:碎石(質量比)=1:4,其7d無側限抗壓強度為1.24MPa,滿足技術規范要求。
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24.1pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>六、結構型式及工藝流程
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基坑回填采用流態粉煤灰,然后用8%石灰土做封層處理,而對于回填范圍內的軟基采用沖擊夯實的辦法。
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normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24.1pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>七、施工控制要點
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>1.基坑在回填之前應清理干凈,并進行夯實,要求壓實度不小于91%,方可進行流態粉煤灰回填。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>2.流態粉煤灰回填時,一定要連續施工,嚴禁施工停頓,以防流態粉煤灰凝結產生分層,影響其整體板體性。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>3.封層石灰土施工需在流態粉煤灰薄膜養生7d后進行。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>4.臺背回填之前對原軟土地基采用大型沖擊壓實機械壓實。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>5.石灰粉煤灰二灰施工嚴禁路拌,要集中場拌,并且嚴格控制其最佳含水量時碾壓,施工時應將表面松散部分計入下層虛鋪。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>6.石灰土碎石施工應嚴格控制配合比,并要求過磅配料。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>7.包邊土寬度為lm,包邊土施工應與各層施工同步進行,并且界限應該明確。
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24.1pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>八、與傳統施工材料、工藝的比較
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>一般傳統的施工材料與工藝是利用石灰土進行分層回填夯實,而新型材料及工藝的應用,克服了填料難以壓實、自重大和強度低等缺點,其優越性與傳統做法相比主要體現在以下幾個發面:
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>1.采用大型的沖擊壓實機械對軟土地基進行壓實,與普通壓實機械相比,可使填前壓實度提高3% ~4%。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>2.基坑回填范圍較小,無法使用大型壓實機具,而流態粉煤灰恰恰克服了這一缺點,無需進行碾壓即可成型。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>3.傳統的石灰土填料壓實容重一般在1.8左右,而主要填料石灰粉煤灰二灰壓實容重一般在1.2左右,從而很好地解決了由于填料自身容重過大產生壓縮變形的可能。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>4.無論是流態粉煤灰、石灰粉煤灰還是石灰土碎石的抗壓強度上均比傳統的石灰土抗壓強度高50%左右,這就為抵抗外界荷載產生變形提供了強有力的保證。
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>5.由于臺背處理范圍由搭板向外
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>6.從排水角度講,該臺背設置了兩層8%石灰土隔水層和整體臺背的高塑指包邊土,可以有效地阻止外界雨水深入,保持路基穩定性,防止由于雨水侵蝕造成的橋頭跳車問題。
normal style="MARGIN: 6pt 0cm; TEXT-INDENT: 24.1pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0; mso-para-margin-top: .5gd; mso-para-margin-right: 0cm; mso-para-margin-bottom: .5gd; mso-para-margin-left: 0cm" align=left>九、結束語
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 24pt; LINE-HEIGHT: 200%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=left>橋頭跳車是公路橋梁的通病,而橋頭臺背的回填是造成橋頭跳車的主要因素,因此臺背回填是工程建設中的一大難點,如何將工程建設中的難點變為亮點,是我們這些工程技術人員的職責。我們只有通過平時施工的不斷積累,科學分析,不斷探索新材料、新工藝,才能提高臺背回填質量,從而消除橋頭跳車,以確保公路運輸的安全暢通。