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>在高速公路建设中,普遍存在一个问题:路面在台背回填处出现不同程度的沉降断裂,据资料显示,最大的沉降值达到
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、工程实例
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>青银高速公路是我国高速公路路网“五纵七横”规划中的重要组成部分,其K105+033处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、桥头跳车对行车速度的影响
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>由于桥台台背沉陷、断裂而形成的台阶,会使车辆的行驶速度受到不同程度的影响。车速的降低幅度与台阶高度、路面类型、道路等级、车辆类型和行驶速度等多种因素有关。根据实地观察和有关资料调查表明,当桥头台阶达
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、桥头跳车原因分析
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.原地基土质不良
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>道路原地表为软土路段,土质较差,容易产生较大地基沉降。由于软土一般都具有天然含水量高、孔隙比大、压缩性强和抗剪强度低等特点,在软土上填筑路基,极易产生沉降(包括瞬时沉降、固结沉降和次固结沉降)。 同时,桥头路基填筑高度较其它地段大,产生基底应力相对较大,更易引起地基沉降,特别是工后沉降较大。
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.基坑回填范围小,大型压实机械不能使用
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>一般桥梁的桥台基坑都相对狭小,不易于使用目前较先进的大型压实机械进行碾压,而且大吨位机械振动力太大时,对桥台有影响。因此在桥台基坑的压实中,往往只能使用小型压实机具,甚至于只能人工夯实,使得回填土不易压实。
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.填料自身容易产生压缩变形
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>与桥台相接的道路路基填方较高,路基填料因含水分,易产生压缩变形,施工中采取任何措施也难将填料颗粒问的孔隙完全消除,在道路自重及车辆的垂直荷载与振动荷载作用下,孔隙率逐渐降低,填料逐渐压缩,密实度逐渐增大,在一定期限内路基产生沉降。因此,压缩沉降主要取决于填料自身的性质、施工条件及台前台背的防护排水工程设置等情况。根据有关资料调查研究:当土堤压实度为95%时,每米填土工后的沉降约为
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.刚性结构与柔性路面过渡界限太明显
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>由于桥台一般采用刚性很大的坚石砌筑或钢筋混凝土浇注而成,具有较大的整体刚度,属刚性体,而与桥台相连的道路,通常采用柔性较大沥青混凝土路面,属弹塑性体。显然,道路与桥台之问存在着较大的刚度差,这个刚度差的存在必然引起道路与桥台之间产生较大的塑性变形相对差和较大的刚度突变,其过渡界限又太明显,这样势必增强桥头跳车的振动效果。
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.路基排水及防渗系统不完善
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>路基排水及防渗系统不完善,长期受到雨水的侵蚀,从而引起路面的竖向变形,产生桥头跳车。
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>针对产生桥头跳车原因分析结果,本工程中决定采用轻质高强的原材料进行基坑回填及台背回填,所用原材料及试验结果如下:
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.原材料试验
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:采用河北临城p032.5R水泥,其技术性能指标见表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 水泥技术性能指标
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>指标 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>初凝时间(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>终凝时间(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抗折强度 (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抗压强度(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:采用石家庄栾城热电厂的湿 排粉煤灰,其技术性能指标见表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 粉煤灰技术性能指标
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>指标 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>比表面积(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>烧失量(%) | 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>三氧化二铝含量(%) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>三氧化二铁(%) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>氧化钙含量(%) | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>氧化镁含量(%) |
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:采用隆尧产生石灰,其有效氧化钙与氧化镁含量为75.6%,满足III级以上生石灰要求,并且要求消解以后过
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)减水剂:采用河北省混凝土外加剂厂生产的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 减水剂技术性能指标
normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>指标名称 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>减水率(%) | 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>凝结时间差 | normal style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 18pt; TEXT-ALIGN: center; mso-pagination: widow-orphan; mso-char-indent-count: 2.0" align=center>抗压强度比(%) | |||
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>终凝 | 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>减水剂 | 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:采用塑性指数大于8的粘性土,作为石灰土及包边土的原材料。经过沿线试验分析比较,决定采用孟村2号土场的粘性土,其塑性指数为8.2,塑限为24.5%,液限为32.4%,满足施工指导书要求。
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.配合比组成设计
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>针对产生桥头跳车的原因分析结果,对原材料进行了多种组成设计,如免于碾压的流态粉煤灰、自重较小的二灰、高强的石灰土碎石等,其配合比设计结果如下:
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)基坑回填采用流态粉煤灰,其配合比组成为:水泥-粉煤灰-水-减水剂(质量比)=6:94:65:0.06,其7d抗压强度为0.442MPa,28d抗压强度为0.690MPa,满足技术规范要求。
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)封层采用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)石灰粉煤灰为台背主要填方材料I其配合比组成为:石灰:粉煤灰(质量比):= 8:100,其7d无侧限抗压强度为0.86MPa,满足技术规范要求。
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范围采用石灰土碎石,其配合比组成为:8%石灰土:碎石(质量比)=1:4,其7d无侧限抗压强度为1.24MPa,满足技术规范要求。
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、结构型式及工艺流程
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基坑回填采用流态粉煤灰,然后用8%石灰土做封层处理,而对于回填范围内的软基采用冲击夯实的办法。
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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、施工控制要点
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.基坑在回填之前应清理干净,并进行夯实,要求压实度不小于91%,方可进行流态粉煤灰回填。
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.流态粉煤灰回填时,一定要连续施工,严禁施工停顿,以防流态粉煤灰凝结产生分层,影响其整体板体性。
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.封层石灰土施工需在流态粉煤灰薄膜养生7d后进行。
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.台背回填之前对原软土地基采用大型冲击压实机械压实。
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严禁路拌,要集中场拌,并且严格控制其最佳含水量时碾压,施工时应将表面松散部分计入下层虚铺。
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.石灰土碎石施工应严格控制配合比,并要求过磅配料。
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.包边土宽度为lm,包边土施工应与各层施工同步进行,并且界限应该明确。
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、与传统施工材料、工艺的比较
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>一般传统的施工材料与工艺是利用石灰土进行分层回填夯实,而新型材料及工艺的应用,克服了填料难以压实、自重大和强度低等缺点,其优越性与传统做法相比主要体现在以下几个发面:
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.采用大型的冲击压实机械对软土地基进行压实,与普通压实机械相比,可使填前压实度提高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.基坑回填范围较小,无法使用大型压实机具,而流态粉煤灰恰恰克服了这一缺点,无需进行碾压即可成型。
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.传统的石灰土填料压实容重一般在1.8左右,而主要填料石灰粉煤灰二灰压实容重一般在1.2左右,从而很好地解决了由于填料自身容重过大产生压缩变形的可能。
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.无论是流态粉煤灰、石灰粉煤灰还是石灰土碎石的抗压强度上均比传统的石灰土抗压强度高50%左右,这就为抵抗外界荷载产生变形提供了强有力的保证。
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.由于台背处理范围由搭板向外
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.从排水角度讲,该台背设置了两层8%石灰土隔水层和整体台背的高塑指包边土,可以有效地阻止外界雨水深入,保持路基稳定性,防止由于雨水侵蚀造成的桥头跳车问题。
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、结束语
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>桥头跳车是公路桥梁的通病,而桥头台背的回填是造成桥头跳车的主要因素,因此台背回填是工程建设中的一大难点,如何将工程建设中的难点变为亮点,是我们这些工程技术人员的职责。我们只有通过平时施工的不断积累,科学分析,不断探索新材料、新工艺,才能提高台背回填质量,从而消除桥头跳车,以确保公路运输的安全畅通。