基坑开挖放坡方案详解

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1目录一、编制依据····················································3二、工程概况····················································31、项目概况··················································32、地质地貌概况··············································43、设计概况·················································44、施工特点··················································4三、施工安排····················································5四、主要施工方法················································51.施工测量···················································52.施工流程···················································53.护坡开挖方案···············································54.排水方案···················································65.土方开挖方案···············································66.基坑开挖后成型图及边坡稳定性计算····························87、土方堆放····················································118、桩基础开挖·················································129、独立柱基础开挖·············································12五、质量保证措施················································13六.安全保证措施················································141.安全管理制度·················································152.安全技术措施·················································1523.施工防护管理·················································164.施工用电·····················································165.施工机械·····················································176、施工道路·····················································18七、雨期施工····················································18八、应急预案····················································191、突发事件应急准备···········································202、突发事件分析及应急预案·····································22九、基坑监测监控················································23十、文明施工、环境保护措施······································243一、编制依据序号名称编号备注1图纸2岩土工程勘察报告3建筑施工手册(第四版)4建筑地基基础工程施工质量验收规范GB50202-20025混凝土结构工程施工质量验收规范GB50204-20156建筑工程施工质量验收统一标准GB50300-20137建筑施工安全检查标准JGJ59-20119施工现场临时用电安全技术规范JGJ46-200510建筑地基基础设计规范GB50007-200211建筑施工土石方工程安全技术规范JGJ180-200912建筑基坑工程监测技术规范GB50497-200913建筑机械使用安全技术规程JGJ33-201214建筑基坑支护技术规程JGJ120-2012二、工程概况1、项目概况本工程为裕达·绿水仙城澳洲青青,位于来宾市武宣县城东新区,规划用地面积为30032.03㎡,总建筑面积159763.50㎡,其中1#~7#楼设计为高4层住宅楼,基础为桩基,8#~11#楼设计为低层商铺,基础为独立柱基础。地下一层,地下室底部设计标高61.00m。参建单位建设单位:武宣裕达房地产开发有限公司勘察单位:核工业桂林工程勘察院设计单位:湘潭市规划建筑设计院监理单位:广东广信建筑工程监理有限公司施工单位:广西裕达工程有限公司2、地质地貌概况现场地已基本开挖至地下室底板,根据岩土工程施工勘察报告显示,本工程场地上覆土层土质情况自上而下主要为:杂填土(第①层Qnl),耕表土(第②层Qpd),坚硬状红黏土(第③层Qel),强风化白云质灰岩(第④层C2h),微风化白云质灰岩(第⑤层C2h)。3.设计概况根据工程勘察院提供《岩土工程勘察报告》资料显示,基坑可放坡开挖,放坡系数可采用1:0.75~1:1.75,结合地质及工程实际情况,本工程采用无支护土方,基坑放坡系数为1:0.75。4.施工特点本工程占地面积较大,土方量较大,周边地面开阔,场地周边20m范围内无建筑物和地下管道,根据地质报告,场地地下水水量贫乏,土质较好。土方采取放坡分层分级开挖,第一层开挖深度为3m,分为2级,每级1.5m,第二层开挖深度为3m,分为2级,每级1.5m,共计开挖深度为6m。5排水采取基坑外排水和基坑内集排水。三、施工安排1.施工进度2016年5月10开工,计划2016年7月15完工。2.劳动力及机械组织根据工程量及总体施工进度要求,计划安排挖土机5台,运土翻斗车10台,水泵4台,挖土机司机5名,运土车司机10名,普通工10人,施工队长一名,技术员一名;。项目安排专业技术负责人3名,质量员3名,安全员3名。四、主要施工方法1.施工测量该工程拟投入的仪器主要有经纬仪和自动安平水准仪、全站仪等。在拟建建筑物四周布设四个水准点,作为建筑物沉降观测的依据,四个水准点闭合差应小于±12√H,场地整理及土方开挖时应保护好水准点。2.施工流程开挖线放样→第一步土方开挖→第一步修坡→开挖下一步土方→下一步修坡→直至基坑底。3.护坡开挖方案(1)放线员用白灰撒好上坡线及下坡线,用于控制放坡角度。根据勘察报告内各土层、土质状况,采用1:0.75坡度放坡。(2)由于基坑较深采用二阶开挖施工,第一阶段挖至3m深处,第二阶段挖6至6m深处,预留0.3m人工清槽。(3)每一开挖阶段均从同方向开始,同时护坡处均一次开挖成型,专人负责指挥作业。(4)基坑四周做1.2米高的临时围栏并挂安全网进行封闭,2米以内不得堆土堆料,夜间设红色警示标志。4.排水方案排水采取基坑外排水和基坑内集排水。在基坑底距坡角500mm处设300×300排水沟,6个集水坑。自然降水及部分○1层土内存水通过上层排水沟排至于集水井,由潜水泵排至城市排水管网,部分○1层土内含水和自然雨水及极弱透水层渗水可通过基坑内排水沟和集水坑直接由潜水泵排至城市排水管网。5.土方开挖方案(1)开挖流程场地清理放灰线甲方或监理验线合格机械就位、开挖装渣外运人工挖土清槽7(2)施工方法a、基坑周围地面堆载应满足以下要求:基坑周围5m范围内堆载不得超过10kpa。b、最后留300mm土采用人工挖,以保护原有土层。c、挖土坡度按照地质勘察报告的放坡系数开挖。d、测量控制:开挖后,测量人员随时进行测量,及时洒灰线,防止超挖和欠挖,操作人员一律使用平锹进行清槽和护坡。e、验收:土方开挖完成后应立即及时组织建设、监理、设计、地勘等部门对基坑进行验收,并浇筑垫层进行封底,防止水浸和暴露。(3)质量标准a、主控项目:开挖标高、长度、宽度、边坡必须符合设计要求。柱基、基坑、基槽、场地的基土土质必须符合实际要求,并严禁扰动。b、一般项目:控制好开挖表面平整度及基底土性。(4)成品保护a、挖运土方时应注意保护定位标准桩、轴线引桩、标准水准点,并定期场地平整进入下道工序(桩孔及独立柱基础开挖)8复测检查定位桩和水准基点是否完好。b、挖土时应对基坑内工程桩做好保护,派专人进行看护,及时与指挥和开挖人员沟通,以防碰撞损坏。6、基坑开挖后成型图及边坡稳定性计算(1)基坑开挖后成型图如下图所示:(2)土坡稳定性计算书a计算依据:依据《建筑基坑支护技术规程》(JGJ120-99)、《建筑基坑支护技术规程》(北京DB11/489-2007)、《土力学与地基基础》等编制。b计算:计算土坡稳定性采用圆弧条分法进行分析计算,由于该计算过程是大量的重复计算,故本计算书只列出相应的计算公式和计算结果,省略了重复计算过程。本计算书采用瑞典条分法进行分析计算,假定滑动面为圆弧面及滑动土9体为不变形刚体,还假定不考虑土条两侧上的作用力。c参数信息条分方法:瑞典条分法不考虑地下水位影响;Ⅰ、放坡参数:───────────────────────────────序号放坡高度(m)放坡宽度(m)平台宽度(m)164.51.0──────────────────────────────Ⅱ、荷载参数:───────────────────────────────序号布置方式荷载值kPa距基坑边线m作用宽度m1满布0.00--------------───────────────────────────────Ⅲ、土层参数:─────────────────────────────序号土类型土厚度(m)γ(kN/m3)C(kPa)φ(℃)饱容重(kN/m3)1粘性土3.0019.00122022.002填土3.0019.00222022.00───────────────────────────────表中:γ为土重度(kN/m3),C为内聚力(kPa),φ为内摩擦角(℃)d、计算原理10根据土坡极限平衡稳定进行计算。自然界匀质土坡失去稳定,滑动面呈曲面,通常滑动面接近圆弧,可将滑裂面近似成圆弧计算。将土坡的土体沿竖直方向分成若干个土条,从土条中任意取出第i条,不考虑其侧面上的作用力时,该土条上存在着:①、土条自重,②、作用于土条弧面上的法向反力,③、作用于土条圆弧面上的切向阻力。将抗剪强度引起的极限抗滑力矩和滑动力矩的比值作为安全系数,考虑安全储备的大小,按照《规范》要求,安全系数要满足=1.2的要求。e、计算公式式子中:Fs--土坡稳定安全系数;c--土层的粘聚力;li--第i条土条的圆弧长度;11γ--土层的计算重度;θi--第i条土到滑动圆弧圆心与竖直方向的夹角;φ--土层的内摩擦角;bi--第i条土的宽度;hi--第i条土的平均高度;h1i--第i条土水位以上的高度;h2i--第i条土水位以下的高度;γ,--第i条土的平均重度的浮重度;q--第i条土条土上的均布荷载;f、计算安全系数将数据各参数代入上面的公式,通过循环计算,求得最小的安全系数Fs:──────────────────────────────计算步数安全系数滑裂角α(度)半径R(m)圆弧角2θ(度)
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