天然气企业市政道路燃气管道工程深基坑开挖专项施工方案

时间：2020-07-06 16:11:04 来源：蒲公英阅读网 本文已影响人

相关热词搜索：开挖 燃气 天然气

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　 天然气 企业 市政 道路燃气 管道工程

　深基坑开挖专项施工方案

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　20××年 1 月 1 日

　 生效日期：20××年 1 月 1 日

　分发部门 ■总经理 ■常务副总 ■财务副总 ■工程副总

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　 1 目 目

　 录

　第一章

　工程概况 ························································ 1

　一、工程简况 ·································································· 1

　二、工程设计概况 ···························································· 1

　三、工程规模及主要 内容 ··················································· 2

　四、地质水文资料 ···························································· 2

　（一）工程地质条件 ····································································· 2

　1、地形地貌 ············································································· 2

　2、气象、水文 ·········································································· 2

　3、地质构造 ············································································· 3

　4、地层岩性 ············································································· 3

　（1）素填土 ························································································ 3 （2）粉质粘土 ····················································································· 3 （3）强风化带岩石 ··············································································· 4 （4）中等风化带岩石 ············································································ 4 （二）水文地质条件 ····································································· 4

　1、在钻探范围内 ······································································· 4

　2、不良地质现象 ······································································· 5

　（三）场地岩土物理力学特征 ························································· 5

　1、素填土 ················································································ 5

　2、粉质粘土 ············································································· 6

　3、强风化带 ············································································· 6

　4、中风化带 ············································································· 6

　5、岩体基本质量等级 ································································· 7

　6、岩土参数选用及建议 ······························································ 7

　（四）场地稳定性及建筑适宜性评价 ················································ 8

　1、地震效应评价 ······································································· 8

　2、基坑边坡评价 ······································································· 9

　3、邻近建（构）筑物影响评价 ····················································· 9

　4、场地稳定性及建筑适宜性评价 ·················································· 9

　（五）地基评价 ········································································· 10

　1、地基的均匀性评价 ······························································· 10

　（1）素填土 ······················································································· 10 （2）场地粉质粘土 ·············································································· 10 （3）基岩 ·························································································· 10 2、岩土层承载能力评价 ···························································· 10

　3、持力层选择及基础型式建议 ··················································· 11

　（1）素填土 ······················································································· 11 （2）粉质粘土 ···················································································· 11

　 2 （3）强风化带岩石 ·············································································· 11 （4）中等风化带岩石 ··········································································· 11 4、桩基成桩可行性评价及桩的施工条件分析建议 ··························· 12

　5、特殊岩土评价 ····································································· 12

　（六）结论及建议 ······································································ 13

　1、结论 ················································································· 13

　2、建议 ················································································· 13

　五、基坑支护工程周边影响及应对措施 ······························· 14

　（一）周边环境对基坑的影响 ······················································· 14

　（二）应对措施 ········································································· 15

　第二章

　编制依据 ······················································· 16

　第三章

　施工计划 ······················································· 17

　一、管理目标 ································································ 17

　（一）质量目标 ········································································· 17

　（二）工期目标 ········································································· 17

　（三）环境保护和安全文明施工目标 ·············································· 18

　二、施工部署 ································································ 18

　（一）施工布署指导思想 ····························································· 19

　（二）施工资源部署 ··································································· 19

　1、时间上的部署原则一季节施工的考虑 ······································· 19

　2、材料与设备计划 ·································································· 19

　（1）主要材料数量表 ··········································································· 19 （2）主要机械设备配置表 ····································································· 20 （3）检测设备投入计划 ········································································ 21 第四章

　施工工艺技术 ················································· 21

　一、悬臂桩及压顶梁施工工艺 ··········································· 21

　（一）旋挖桩施工工艺流程图 ······················································· 21

　（二）桩位测量及定位 ································································ 22

　（三）旋挖机就位 ······································································ 23

　（四）旋挖钻进成孔 ··································································· 23

　（五）终孔 ··············································································· 24

　（六）清孔 ··············································································· 25

　（七）钢筋笼制作与安装 ····························································· 25

　（八）混凝土灌注 ······································································ 26

　（九）常见的灌注桩质量问题及控制对策 ········································ 28

　1、测量程序 ··········································································· 28

　2、出现偏桩主要成因 ······························································· 28

　3、蹋孔管控 ··········································································· 28

　4、桩身夹泥及断桩管控 ···························································· 29

　 3 5、烂桩头管控 ········································································ 29

　（十）灌注桩管理措施 ································································ 30

　（十一）压顶梁施工 ··································································· 31

　二、土方分层开挖及桩间挡土板施工 ·································· 32

　（一）施工流程 ········································································· 32

　（二）便道放坡 ········································································· 32

　（三）分层开挖 ········································································· 33

　（四）临时排水设施 ··································································· 33

　（五）其它要求 ········································································· 33

　第五章

　施工安全保证措施 ··········································· 34

　一、安全组织机构 ·························································· 34

　二、安全管理 ································································ 36

　三、安全保证措施 ·························································· 37

　（一）安全保障检查程序 ····························································· 37

　（二）安全保障检查内容 ····························································· 38

　四、安全技术措施 ·························································· 40

　（一）一般措施 ········································································· 40

　（二）土石方开挖措施 ································································ 41

　（三）挖孔桩措施 ······································································ 42

　五、安全事故应急预案 ···················································· 42

　（一）编制目的及环境概况 ·························································· 42

　1、编制依据及目的 ·································································· 42

　2、周边环境概况 ····································································· 43

　（二）重大危险源辨识 ································································ 43

　1、火灾爆炸 ··········································································· 43

　2、触电 ················································································· 43

　3、机械伤害 ··········································································· 43

　4、高处坠落 ··········································································· 43

　5、坍塌 ················································································· 43

　6、传染性疾病 ········································································ 43

　7、化学物品泄漏 ····································································· 43

　8、灾害性天气 ········································································ 43

　9、烧伤 ················································································· 44

　10、交通事故 ········································································· 44

　（三）应急救援工作原则 ····························································· 44

　（四）应急救援工作组织 ····························································· 44

　1、应急救援组织机构的主要职责 ················································ 44

　2、成立应急救援组织机构 ························································· 45

　3、应急响应 ··········································································· 45

　4、坍塌事故的应急措施 ···························································· 45

　 4 5、基坑支护、模板工程发生的坍塌事故的应急措施 ························ 46

　6、脚手架坍塌事故的应急措施 ··················································· 46

　7、应急救援预案的启动、终止和终止后工作恢复 ··························· 46

　六、基坑监测 ································································ 47

　（一）基坑施工监测的主要内容 ···················································· 47

　（二）基坑顶部沉降和位移监测 ···················································· 47

　1、测点布置 ··········································································· 47

　2、测试手段 ··········································································· 48

　3、测点埋设 ··········································································· 48

　七、环保措施 ································································ 48

　第六章

　劳动力计划 ···················································· 49

　第 1 页

　共 50 页 第一章

　工程概况

　一、工程简况

　工程名称：天然气分布式能源项目-能源站工程 工程地点：

　设计单位：

　建设单位：

　监理单位：

　总包单位：

　施工单位：

　二、工程设计概况

　本工程共计 109 平方米，结构形式桩基础、剪力墙结构，地上 2层，地下-层。全部为现浇楼面，檐口最高 8.5 m。结构抗震等级为三级。

　本项目以天然气管道为开挖，场地内地下没有管网，线缆等埋藏物。西南侧 15 米外为××××大道城市道路；西北侧建筑红线外为小区公路，12 米外为小区住宅楼；东北侧 5 米外为拟拆除医院住宅楼；东南侧 4 米外为医院门诊楼及地下车库。场地周边地形复杂，交通方便，拟建场地部分为回填土，场内地势平整。基坑东南侧边坡放坡坡率缓于 1:1.5；其它三方采用结构支护。

　第 2 页

　共 50 页 三、 工程规模及主要内容

　（一）本次编制内容为××××天然气分布式能源项目能源站深基坑开挖工程，其中基坑周长约 110m，坑深 8m。环境高程 316，基坑开挖深度相对于士 0.000mm 标高为-8 米。

　（二）项目地块南北向长约 34m，东西向长约 21m，呈方形，土石方工程量约 5712 立方米；其中石方约 200 立方米，土方约 5512 立方米。场地西南侧为城市道路—××大道，交通方便，拟建场地部分为回填土，场内地势平整。

　四、地质水文资料

　（一）工程地质条件

　1 1 、地形地貌

　勘察区现状为回填地形，地形坡角一般在 0°～5°之间。地面标高在 315.50m（ZY9）～316.29m（ZY3）之间，相对高差约 0.79m左右。

　综上所述，拟建区地形地貌简单。

　2 2 、 气象、水文

　场地位于××市××开发区，交通便利。勘察区属亚热带季风气候区，温暖湿润，四季分明，年均气温 17.5℃～18.5℃，极端气温-1.8℃～41.9℃，四季分明。年平均降雨量 1141.8mm，降雨主要集中于 5-9 月，且常有雷阵暴雨。春冬多雾，雾日最长达 148 天。年平均相对湿度 80%，绝对湿度 17.6mb。常年风速较小，以偏西北风见多，

　第 3 页

　共 50 页 最大风速为 28.4m/s（摘自××气象简报）。

　3 3 、 地质构造

　场内构造属东山背斜的南东翼，岩层呈单斜产出，层面平直光滑，无胶结，结合程度很差，属软弱结构面，产状 105°∠15°，岩层变化总体不大。在岩层中测得裂隙主要有两条：

　（1）产状为 210°∠65°，裂面平直，间距 2～4m，延伸 3m，裂隙宽 1-10mm ，结合程度差，属软硬性构面。

　（2）产状为 320°∠70°，裂面平直，间距 1～3m，延伸 5～8m，裂隙宽 0.5～12mm，裂面为泥质充填，结合程度差，属硬性结构面。场地构造裂隙总体不发育。调查区内及附近周边未见构造断层通过。

　4 4 、 地层岩性

　场内揭露地层岩性主要为第四系全新统素填土（Q4ml）残坡积层粉质粘土（Q4el+dl）及侏罗系中统沙溪庙组泥岩、砂岩（J2s），基岩按风化程度划分为强风化带、中等风化带。

　现自上至下分述如下：

　（1 1 ）素填土

　杂色，主要由块石和粉质粘土组成，土石比约 7：3～8:2，块石最大粒径约 18mm，稍湿、稍密，由机械推填而成，填龄不足 5 年，场地均有分布，分布厚度：3.5（ZY3）～6.6m（ZY7）。

　（2 2 ）

　粉质粘土

　红褐色，主要由粘粒组成，可塑，韧性、干强度中等，无摇震反应，稍有光泽，场地均有分布，分布厚度：1.8（ZY7）～3.4m（ZY4）。

　第 4 页

　共 50 页 （3 3 ）

　强风化带岩石

　岩性为紫红色泥岩、暗紫红色砂岩，岩石裂隙发育，质软，破碎，岩芯不完整，岩石结构构造被风化破坏，岩芯多呈碎块状，厚度 1.3（ZY9）～2.2m（ZY5）。

　（4 4 ）

　中等风化带岩石

　泥岩紫红色，泥质结构，中～厚层状构造，粘土矿物为主，局部含砂质团块或条带，岩体较完整，节长 11～30cm。

　砂岩暗紫红色，细粒结构，钙泥质胶结，中-厚层状构造，局部泥质胶结，质软，岩体较完整，节长 10～22cm。

　（二）水文地质条件

　1 1 、 在钻探范围内

　场地地层结构上覆土层为第四系全新统人工填土（素填土）和残坡积粉质粘土，下伏基岩为侏罗系中统沙溪庙组泥岩和砂岩。泥岩、粉质粘土为相对隔水层，砂岩、素填土为含水层，赋水条件差；从场区水文地质条件分析，场区地势总体较平坦，地表水不易排泄。地下水类型属上层滞水，据现场水文地质观测，场地内钻孔多呈干孔状态。并在 ZY3 作简易抽水试验，数筒即干，24 小时后，未见恢复水位。故场地在钻探控制深度范围内地下水贫乏，水文地质条件简单。

　由于场地有基坑开挖，雨季时，容易汇集雨水，建议做好降水井等降水排水措施，同时采取有效的防渗措施对污水、废水、脱氯池作防渗处理。

　据现场地面调查和附近工程调查表明：

　第 5 页

　共 50 页 根据规范《岩土工程勘察规范》（GB50021-2001）（2009 年版）判定，地下水及地基土对混凝土结构有微腐蚀，对钢筋混凝土结构中的钢筋有微腐蚀，对钢结构有微腐蚀。

　2 2 、 不良地质现象

　根据现场地质调查及钻探揭露，场内及邻近未发现滑坡、崩塌、泥石流等不良地质现象。

　（三）场地岩土物理力学特征

　1 1 、素填土

　杂色，分布于整个场地，据场地实际情况，在 ZY1、ZY2、ZY5、ZY6、ZY7、ZY8 六孔作重型动力触探测试，以进一步评价填土工程特性。试验成果详见下表。

　重型（ N63.5 ）动力触探成果统计表

　土层名称

　孔号

　试验厚度（m m ）

　锤击数

　变异系数

　平均值

　厚度加权平均值

　密实度

　素填土

　ZY 1 3.7 5.14 0.427 5.27 5.27 稍密 ZY2 4.4 5.22 0.432 ZY 5 3.8 5.28 0.419 ZY6 4.0 5.56 0.431 ZY 7 4.4 5.17 0.430 ZY8 3.8 5.25 0.418 经杆长校正后，每贯入 10cm 的锤击数，其最小值为 1.0，最大值为 10.9，平均值为 5.27，厚度加权平均值 5.27，变异系数 0.418～0.432，可判定场地素结构稍密，均匀性差。建议场地素填土天然重度（经验值）取 20.00KN/m³，饱和重度（经验值）取 20.50KN/m³，粘聚力天然状态取 5KPa，饱和取 0KPa，天然综合内摩擦角取 30°，

　第 6 页

　共 50 页 饱和综合内摩擦角取 25°。

　2 2 、粉质粘土

　红褐色，呈可塑状态。该土层厚薄较薄，且不均，故未取样试验。根据现场情况并结合当地经验，建议天然重度（经验值）取 19.00KN/m³，地基承载力（经验值）取 150KPa。

　3 3 、强风化带

　场地内强风化带岩石结构不清晰，岩石破碎，取样困难，故未取样试验。据现场鉴别岩芯及结合经验，建议强风化带岩石地基承载力特征值（经验值）：泥岩（强风化状）取 300kPa，砂岩（强风化状）取 350kPa；建议强风化带岩石天然重度（经验值）：泥岩（强风化状）取 24.50KN/m³，砂岩（强风化状）取 23.50KN/m³。

　4 4 、中风化带

　场地中等风化带岩石为泥岩、砂岩，岩体较为完整，是良好的基础持力层。通过对场地中等风化带岩石取样作天然重度、天然、饱和单轴抗压强度试验，岩石抗压强度标准值采用概率统计法进行计算（《岩土工程勘察规范》GB50021-2001（2009 年版）

　（14.2.4-1）公式），公式如下：

　øk=γsøm γs=21.704 4.6781 { }n n  

　  ninfinnifi f1) (211] [21

　 fmf  

　第 7 页

　共 50 页 式中：

　δf：岩土参数的标准差 øm：岩土参数的平均值 øk：岩土参数的标准值 δ：岩土参数的变异系数。

　岩石参数试验成果详见下表。

　中等风化带岩石抗压强度成果统计表

　岩石名称

　试验项目

　统计数目

　岩样编号

　抗压强度单值 （ Mpa ）

　数据分布范围

　平均值（ Mpa）

　）

　软化系数

　标准差

　变异系数

　标准值（ Mpa ）

　泥

　岩 天

　 然 9 ZY1-A1-A6 6.15 6.78 5.59 4.30 5.84 0.53 0.72 0.12 5.39 ZY6-A1-A6 5.75 6.27 5.35 ～ ZY7-A1-A6 6.40 6.00 4.30 6.78 饱

　 和 9 ZY1-A1-A6 3.32 3.88 3.12 2.10 3.11 0.56 0.18 2.76 ZY6-A1-A6 3.19 3.86 2.96 ～ ZY7-A1-A6 3.00 2.60 2.10 3.88 砂

　岩 天

　 然 9 ZY1-S1-S6 24.70 26.40 23.80 16.80 21.27 0.78 3.32 0.16 19.14 ZY6-S1-S6 22.30 20.40 20.90 ～ ZY9-S1-S6 16.80 18.70 17.40 26.40 饱

　 和 9 ZY1-S1-S6 18.20 20.00 17.80 10.80 15.08 3.18 0.21 13.09 ZY6-S1-S6 16.00 13.90 14.70 ～ ZY9-S1-S6 10.80 13.00 11.30 20.00 5 5 、岩体基本质量等级

　据野外岩芯鉴别和计算统计结果：中等风化泥岩饱和单轴抗压轻度标准值 2.76MPa，按坚硬程度划分为极软岩，按较完整岩体，岩体基本质量等级划分为Ⅴ类;中风化砂岩饱和单轴抗压轻度标准值13.09MPa，按坚硬程度划分为软岩，按较完整岩体，岩体基本质量等级划分为Ⅳ类。

　6 6 、岩土参数选用及建议

　据试验成果统计分析，本次勘察野外鉴别及地区经验，本工程场

　第 8 页

　共 50 页 地设计所需的各岩土参数建议取值详见下表。

　本次钻探揭露粉质粘土岩土参数参照地区经验进行取值；强风化基岩的地基承载力特征值根据野外鉴别按地区经验取值；中等风化岩石地基承载力特征值 fa 按《建筑地基基础设计规范》GB50007-2011规定的公式计算（按饱和单轴抗压强度标准值折减，岩体较完整，折减系数取 0.33）。

　临时边坡坡率值按有关规范和××地区经验取值。

　岩土设计参数建议取值

　项目

　岩土名称

　天然重度

　（ kN/m ³）

　饱和重度

　（ kN/m ³）

　岩石单轴极限抗压强度标准值（ MPa ）

　基地摩擦系数

　水平抗力系数（ MN/m ³）

　水平抗力系数的比例系数（ MN/m4）

　）

　地基承载力特征值fa （ kPa）

　）

　临时基坑坡率值

　天然

　饱和

　素填土

　20.00* 20.50* / / / / 6* / 1:1.5 粉质粘土

　19.00*

　/ / 0.20 / 14* 150* 1:1.25 强风化泥岩

　24.50*

　/ / 0.30 20* / 300* 1：0.75 中风化泥岩

　25.50*

　5.39 2.76 0.40 40* / 910.8 1:0.5 强风化砂岩

　23.50*

　/ / 0.35 20* / 350* 1:0.75 中风化砂岩

　24.60*

　19.14 13.09 0.45 140* / 4319.7 1:0.5 （四）场地稳定性及建筑适宜性评价

　1 1 、 地震效应评价

　根据《建筑抗震设计规范》GB50011-2010 附录 A，本区抗震设防烈度为 6 度，设计基本地震加速度值为 0.05g，设计地震分组为第一组。根据《建筑抗震设防分类标准》GB50223-2008，建筑物抗震设防类别应不低于标准设防类（丙类），应按本地区抗震设防烈度确定其抗震措施和地震作用，属一般建筑，可按标准设防。

　各拟建物按不利原则考虑，地震效应具体评价详见下表：

　第 9 页

　共 50 页 各拟建楼土 层等效剪切波速及场地类别划分表

　拟建物名称

　环境标高（m m ）

　υe se 计算位置

　填土

　粉质粘土

　整平后覆盖层最大厚度（m m ）

　等效剪切波速（ m/s ）

　建筑场地类别

　场地土类别

　设计特征周期（s s ）

　抗震地段划分

　厚度（m m）

　）

　波速（ m/s）

　）

　厚度（m m ）

　波速（ m/s）

　）

　能源/污水处理站 316.00 ZY5 2.94 120 2.8 150 5.74 132.97 Ⅱ 软弱土 0.35 一般地段 废水处理池 316.00 ZY5 2.94 120 2.8 150 5.74 132.97 Ⅱ 软弱土 0.35 一般地段 脱氯消毒池 316.00 ZY9 2.00 120 3.2 150 5.20 136.84 Ⅱ 软弱土 0.35 一般地段 注：上述土层剪切波速为地区经验值。

　据上表计算结果表明：场地类别均为Ⅱ类，软弱土，设计特征周期为 0.35s，属对抗震一般地段。

　拟建场地设防烈度为 6 度，区内未见可能液化的砂土分布，地势平坦，地震作用对岩、土层影响小，在地震作用失稳可能性较小。

　2 2 、 基坑边坡评价

　拟建场地按照设计标高整平后，将形成高 3.50-4.00m 的土质边坡。具体评价详见表 11。

　3 3 、 邻 近建（构）筑物影响评价

　拟建场地南东侧直线距离约 5m 处为医院已建门诊楼，高 22.35m，层高-1F/6F，设计地坪标高为 316.10m。勘查区基坑为土质边坡，且坡高较低，对相邻构筑物的影响小。对场地回填整平后，修建处理池时，应修建挡墙支挡，即先支挡再开挖（采用桩板挡墙支档），同时对相邻建筑物的稳定进行监测，以此来确保已有建筑物的安全。

　4 4 、 场地稳定性及建筑适宜性评价

　场地按±0 标高及环境标高整平后，对基坑边坡处理后，场地与

　第 10 页

　共 50 页 地基稳定，适宜本工程建设。

　（五）地基评价

　1 1 、 地基的均匀性评价

　（1 1 ）

　素填土

　主要由块石、粉质粘土组成，土石比约 7:3～8:2，块石最大粒径约 18mm，场区均有分布，厚薄不均匀，均匀性差，主要靠自重应力固结，密实度为稍密，其工程特性差，承载能力低。

　（2 2 ）

　场地粉质粘土

　呈可塑状态，该层局部分布，厚薄不均，其工程特性差，承载能力低。

　（3 3 ）

　基岩

　为良好的基础持力层，其地基力学性质较好；强风化泥岩地基承载力经验特征值取 300KPa，强风化砂岩地基承载力经验特征值取400KPa；中风化泥岩天然单轴抗压强度标准值为 5.39MPa，中风化砂岩饱和单轴抗压强度标准值为 13.09MPa。

　2 2 、 岩土层承载 能力评价

　特殊土素填土：未经碾压密实，具湿陷性，压缩性，不均匀性，透水性，工程特性差，承载力低； 粉质粘土：厚度较薄，分布不均匀，承载力低； 强风化基岩岩体破碎-较破碎，主要呈碎块状少量短柱状，力学性能较好，承载能力较高； 中等风化基岩，岩体较完整，岩体基本质量等级为Ⅳ类，力学性

　第 11 页

　共 50 页 能好，承载能力高。

　3 3 、 持力层选择及基础型式建议

　（1 1 ）

　素填土

　厚度不均匀，结构稍密，不宜选做基础持力层。

　（2 2 ）

　粉质粘土

　厚度不均匀，不宜选做基础持力层。

　（3 3 ）

　强风化带岩石

　结构构造被风化破坏严重，裂隙发育，按±0 设计标高整平后，根据埋藏深度及拟建物情况，可选作部分拟建物浅基础持力层。

　（4 4 ）

　中等风化带岩石

　岩体较完整，力学性质较好，是拟建物良好基础持力层。

　据工程地质勘察技术委托书，拟建物为砖混结构，拟采用桩筏基；拟建楼整平至各自的设计地坪高程后其持力层岩性、持力层埋深及基础型式建议详见下表。

　基础型式建议

　拟建物名称

　层数

　结构类型

　持力层埋深（m m ）

　持力层岩性

　建议基础型式

　能源/污水处理站 -1/2F 砖混 6.71-11.94 中风化基岩 桩筏基 废水处理池 / 砖混 10.38-4.94 中风化基岩 桩筏基 脱氯消毒池 / 砖混 9.50-11.94 中风化基岩 桩筏基 备注：1、桩筏基础设计时，统一取中等风化带砂岩饱和抗压强度标准值 13.09Mpa；泥岩天然抗压强度标准值 5.39 Mpa，供设计使用。

　当采用桩筏基础时，单桩竖向极限承载力标准值建议按《建筑桩基技术规范》JGJ 94-2008 第 5.3.9 条公式计算。后期回填土应考虑

　第 12 页

　共 50 页 负摩阻力，负摩阻力系数取 0.30，建议设计采取有效隔离措施，以减少或消除负摩阻力的影响（采用压实填土，当压实系数≥0.94 时，可不考虑负摩阻力的影响。）桩周土侧阻力标准值：强风化带基岩取150Kpa。

　4 4 、 桩基成桩可行性评价及桩的施工条件分析建议

　场地内分布土层有素填土（稍密），厚度约 3.5～6.6m、粉质粘土（可塑）厚度约 1.8～3.4m。由由于部分地段土层厚度较大，人工挖孔桩施工难度大；且根据市建委相关规定，建议不采用人工挖孔桩。根据场地条件，建议采用机械成孔桩工艺。机械成孔桩有施工噪音扰民和泥浆污染环境，注意控制泥浆污染。若一定要采用人工挖孔桩，必须先进行人工挖孔桩的可行性专项论证。

　由于土层及碎块石等影响；旋挖桩施工容易产生偏心、垮孔、沉渣厚度过大、混凝土离析等现象，施工中应加强护壁措施，应严格控制桩底沉渣，浇筑过程中应控制浇筑管提升速度并在浇筑管底端设置浇筑盖。施工过程中应加强桩身垂直度、沉渣、桩身质量和桩端持力层检验。

　5 5 、 特殊岩土评价

　拟建场地内特殊岩土为素填土、粉质粘土，未见其它特殊岩土。拟建场地内素填土，主要由块石、粉质粘土等组成，土石比约7:3-8:2，未经碾压密实，密实度为稍密，均匀性差；场地及附近周边未见污染源，地下水及地基岩、土对混凝土及混凝土中的钢筋、对钢结构具微腐蚀性。

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　共 50 页 （六）结论及建议

　1 1 、 结论

　（1）拟建场地及邻近未发现危岩崩塌、滑坡、泥石流等不良地质作用。场地与地基稳定，适宜本工程建设。

　（2）场地内桩孔（坑）雨季施工时，桩孔（坑）内有地下水及地表水，故基础施工时需加强排水措施。地下水及各岩、土层对混凝土结构、对混凝土中钢筋、对钢结构具微腐蚀性。

　（3）场地抗震设防烈度为 6 度，设计基本地震加速度值为 0.05g，设计地震分组为第一组。根据《建筑抗震设防分类标准》GB50223-2008，抗震设防类别应不低于标准设防类（丙类），应按本地区抗震设防烈度确定其抗震措施和地震作用。拟建场地内见可能液化的砂土分布，地势平坦，地震作用小，在地震作用下岩、土层失稳可能性较小。

　2 2 、 建议

　1、施工顺序：先平场至设计地坪标高及环境标高位置再对拟建场地内基础进行施工。

　2、建议在场地周边及内部设置良好的排水系统，避免地表及大气降水汇聚渗入地基对地基及基础造成不良影响。

　3、采用桩筏基础（人工挖孔桩）时，应按××市 2012（162）文要求进行专家专项论证，方可实施，并对上部土层及易破碎强风化带砂岩段采取加筋砼护壁措施，以防止孔壁垮塌，并加强通风措施，严防沼气中毒。雨季施工时，桩孔内有大量积水，应及时进行抽排，

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　共 50 页 并采取积极有效的防治措施，（采取钻孔降水）设计及施工单位严格执行 DBJ50-200-2014 桩基设计及施工的相关内容，确保井下作业人身安全。

　4、场地内基础施工时，应加强施工安全管理，独立柱基重视基坑壁的安全，并采取适当的支护措施，（深度＞2.5m）或严格采取临时放坡措施。

　5、采用桩基础时，应对桩基与填土进行有效隔离，否则应考虑填土不均匀沉降对桩侧引起的负摩阻力。场地内中等风化岩石其物理力学性质指标具有一定的变异性，施工时可能在局部地段或部分桩位岩石抗压强度实测值略低或高于标准值的情况，建议设计时予以考虑并预留调整措施，本报告中的...