10.3基坑土方开挖施工方案

基坑土方开挖施工方案(H=﹣3.5m)1基坑土方开挖施工方案(H=﹣3.5m)（仅供参考）目录1工程概况····························································································································12施工策划····························································································································13施工方法····························································································································23.1施工顺序··························································································································23.2施工准备··························································································································23.3场地平整··························································································································33.4测量放线··························································································································33.5轻型井点降水··················································································································33.6土方开挖··························································································································43.7基坑排水··························································································································63.8垫层浇捣··························································································································64质量保证措施·····················································································································75安全保证措施·····················································································································76保洁措施····························································································································81工程概况本工程位于××路，其南临××路，北临××路，西临××路。本标段由组成部分，1＃、2＃楼基坑呈长方形，基坑宽约18m，长约52m。基底标高为-3.650m，-4.050m，-4.650m，局部最深处达-4.880m，基坑开挖采用大面积开挖，以1:1.5放坡，基坑挖深约2.2m，局部最深约3.5m，1＃、2＃楼预计土方约3000m³。本工程基坑开挖前采用轻型井点预降水，挖土时采取明排水，共设4套轻型井点设备。2施工策划2.1指导思想：为确保在基坑挖土施工，应遵循两个“万无一失”的原则，即“安全万无一失”，对周围环境“万无一失”。挖土时必须做到“快挖快覆混凝土”。2.2由于基坑采用轻型井点，为防止土体塌方，基坑开挖边坡必须采用1:1.5基坑土方开挖施工方案(H=﹣3.5m)2大放坡，以确保土体稳定。2.3本工程挖土量大，工期紧，进出道路狭小，施工难度高。充分考虑基坑挖土、外运土、进出道路、截桩、保洁、人工修土配合等各方面的因素，必须采用最佳的施工方法，合理安排，确保本工程顺利施工至结束。在挖土开始前，预先在基坑内土方运输车行驶路线上铺设好走道板，以保证土方运输车辆正常行驶畅通。2.4挖土施工由l台1.6m³和1台1.2m³挖机，自l＃楼向2＃楼边退边挖，最后于2＃楼收口。1台挖机l个台班可出土500m³，挖土工期预计为6天。3施工方法3.1施工顺序施工准备→场地平整→测量放线→轻型井点施工→井点降水→土方开挖（同时截桩，修土）→浇硅垫层→深基坑土方开挖（同时截桩、修土）→浇砼垫层3.2施工准备3.2.1组建项目指挥部本工程挖土量约3000m³，由于仅局部采取降水措施，施工难度大，为确保工程顺利进展，首先组建一个项目指挥部，总指挥下设：技术组：主要负责施工方案的制作及施工过程中技术问题的处理。土方组：主要负责基础土方挖土、外运、弃土场地。配合组：配合前方施工、机械维修及路口指挥、保洁等。施工管理网络（编者略）3.2.2设备准备根据施工要求，及时落实好施工设备以及配套的其它设备材料、工具等，以确保工程顺利施工。计划投人设备如下：设备名称数量备注挖机EX200挖机PC200111.6m³1.2m³走道板（钢板）10块塔吊140吨米运土车辆5辆15吨轻型井点4套基坑土方开挖施工方案(H=﹣3.5m)33.2.3弃土点落实弃土地点甲方指定。3.2.4办理好有关手续根据上海市有关文件，结合现场施工实际情况，在开工前必须和有关部门联系，搞好协调工作，办理好所有有关手续，以保证顺利开工。3.2.5现场施工管理准备施工前，指挥部负责带领各部门施工组，对施工项目的质量、进度、工期进行交底，对施工方案进行详细的讨论、研究，做到分工明确，责任明确，要求明确。指挥部负责每天召开施工协调会，认真听取采纳甲方和监理的意见和方案，布置当天施工任务，处理施工中发生的一切生产、技术对外协调问题，各部门按要求做好每天的施工记录，做到准确无误。3.3场地平整土方开挖前，首先进行场地平整，把以前所遗留下的建筑垃圾清除干净，修建施工现场临时道路，埋设好施工用水，用电管线，确保三通一平。沿西侧围墙边设置排水沟、沉淀池，基坑周边设挡水坎，保证雨天场地不积水，地表水不进人基坑。3.4测量放线设置测量控制网，包括基线和水平基准点，设在不受基础施工影响处，基坑开挖前，根据控制线放出基坑灰线（边线），放线时应按要求放出边坡宽度。灰线、标高、轴线应进行复核，检查无误后报监理审定方可进行挖土施工。3.5轻型井点降水考虑本工程基坑较深，为不影响基坑土方的正常顺利开挖，在挖土前，采用轻型井点降水，降水至挖土面以下0.5m处。3.5.1井点布置及设备选用根据l＃~2＃楼所处位置、形状及挖土深度，l＃楼轻型井点选用U线状井点（即沿南西北方向布置）,2＃楼轻型井点选用封闭型线状井点，共4套轻型井点基坑土方开挖施工方案(H=﹣3.5m)4设备，总管直径选用ф125，井点管直径选用ф48，井点管高4.5（包括1.5m滤管），井点管排列间距为1.5m。共布置4套抽水设备。3.5.2井点管的埋设3.5.2.1埋设顺序先埋设总管，再埋设井点管，用弯管将井点管和总管连通，然后安装抽水设备。3.5.2.2埋设方法井点管埋设分振动水冲孔与埋管两个过程。冲孔直径为300mm，深度应比滤管深0.5m左右，冲孔后立即拔出冲管，居中插人井管，并在井点管与孔壁之间迅速填灌砂滤层。砂滤层填灌要保证间距均匀。滤砂宜选用干净粗砂，填灌均匀，灌砂高度2m以上以保证水流畅通。井点管填砂后，用粘土封口，以防漏气。井点管埋设完毕，应接通总管与抽水设备进行试抽水，检查有无漏水、漏气、出水是否正常，有无放塞现象，如有异常情况，应检查修好后方可使用。3.5.2.3井点管的使用井点使用时，应保证连续不断地抽水，并准备双电源。正常出水规律是“先大后小，先混后清”。地下室底板砼浇筑后，将轻型井点系统拆除，所留孔洞用砂填塞堵满。井点降水时，应对水位降低区域内的建筑物进行沉陷观测，发现沉陷或水平位移过大时，应及时采取防护技术措施。3.6土方开挖因本工程基坑内含有试桩，因此，挖土过程中要配备足够的人员进行截桩、修土工作，保证截桩、修土工作紧跟挖机作业，以保证施工的连续性，确保按预定的计划完成施工任务。3.6.1挖土方法3.6.1.1土方开挖前，首先分别在1＃、2＃楼基坑范围外1m处埋设井点降水管，以便降低地下水位，利于日后挖土。3.6.1.2本工程土方开挖采取大面积开挖，即自l＃楼向2＃楼后退开挖，共投放两台挖机同时挖土。3.6.1.3吸取以往基坑挖土的教训，本工程基坑采取轻型井点降水。井点布基坑土方开挖施工方案(H=﹣3.5m)5置详见附图（编者略）。3.6.1.4基坑大开挖边坡按1:1.5放坡。由于l＃楼东侧距临建仅5.2m，施工主道路1.2m，不能满足1:1.5放坡要求，故采取300宽9m钢板桩护坡，以确保土体稳定。3.6.1.5根据标高控制，一次挖到基坑底面以上300mm，余土及附带在基础桩上及周围挖机挖不到的地方，由配合挖土人员尽快挖除，并及时抛至挖机工作面内，以便把余土全部带出，做到挖一块，清一块。在挖土过程中注意对工程桩的保护，严禁挖土机械碰击工程桩。若在挖土过程中遇地下暗滨，则在暗滨内铺填块石，经监理验收后再铺填碎石，以保持基底稳固平整。基坑挖好后，应对基底进行抄平，修整，并向监理报验。为防止坑底扰动，基坑挖好后，并及时进行砖垫层浇筑。3.6.2挖土标高控制机械挖土标高控制在基底以上300mm处，余下土方改用人工挖土至底标高，标高误差及平整度均严格按规范标准执行。机械挖土接近坑底约500mm时，由现场专职测量员用水平仪交水准标高引测至坑底，然后随挖机逐步向前推进，将水平仪置于坑底，每隔2-3m调置一标高控制点，纵横向组成标高控制网，以准确控制基底标高，严禁超挖。3.6.3边坡稳定安全措施3.6.3.1做好地面及基坑排水措施，避免场地周围及基坑内积水，以防造成边坡塌方。3.6.3.2边坡开挖应采取沿等高线自上而下分层、分段依次进行，严格按1:1.5坡度进行放坡，避免先挖坡脚，造成坡体失稳。3.6.3.3为防止超挖和保持边坡坡度正确，机械开挖至接近坑底标高或边坡边界，应予留300mm厚土层用人工开挖和修坡，保持边坡有足够的坡度，避免随意切割坡体的坡脚。每挖lm应检查边线和边坡，随时纠正偏差。3.6.3.4为防止边坡滑坡，挖土上边缘距边坡坡脚不得小于2m。3.6.3.5若发现滑坡裂缝，应及时填平夯实，对可能出现的浅层滑坡，如滑坡土方量不大时，将滑坡体全部挖除。对于已出现的滑坡可采取卸荷减重，