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随着建筑高层的增加，根据构造及使用要求，基础埋深也随之不断增加，这样就出现了大量的深基坑工程，且城市基坑工程往往处于房屋和生命线工程的密集地区，很多情况下不同意采纳比较经济的放坡开挖，而需要在人工支护条件下进行基坑开挖，为了保证基坑周围的建筑物、地下管线、道路等的安全，应大力研究深基坑支护技术。 一、深基坑工程的主要内容
1、岩土工程勘察与工程调查。确定岩土参数与地下水参数；测定邻近建筑物、周围地下埋设物、城市道路等工程设施的工作现状，并对其随地层位移的限值作出分析。
2、支护结构设计。包括挡土墙围护结构（如连续墙、柱列式灌注桩挡墙）、支承体系（如内支撑、锚杆）以及土体加固等。支护结构的设计一定与基坑工程的施工方案紧密结合，需要考虑的主要依据有：当地经验，土体和地下水状况，四周环境安全所同意的地层变形限值，可提供的施工设施与施工场地，工期与造价等。 3、基坑开挖与支护的施工。包括土方工程、工程降水和工程的施工组织设计与实施。
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4、地层位移预测与周边工程爱护。地层位移既取决于土体和支护结构的性能与地下水的改变，也取决于
施工工序和施工过程。如预测的变形超过同意值，应修改支护结构设计与施工方案，必要时对周边的重要工程设施采取专门的爱护或加固措施。
5、施工现场量测与监控。根据监测的数据和信息，必要时进行反馈设计，用信息化来指导下一步的施工。
二、深基坑支护结构类型
1、钢板桩支护
钢板桩应用于建筑深基坑的支护，是一种施工简洁，投资经济的支护方法。在上海软土地区过去应用较多，但由于钢板桩本身柔性大，如支撑或锚拉系统设置不当，其变形会很大。因此对基坑支护深度达7m以上软土地层，基坑支护不宜采纳钢板桩支护，除非设置多层支撑或锚拉杆，但应考虑到地下室施工结束后钢板桩拔除时对周围地基和地表变形的影响。
2、地下连续墙
地下连续墙是在泥浆护壁的条件下分槽段构筑的钢筋混凝土墙体，地下连续墙最早于1950年开始应用于巴黎和米兰市的地下建筑工程。由于地下连续墙具有整体刚度大和防渗性好，适用于地下水位以下的软粘土和砂土多种地层条件和复杂的施工环境，尤其是基坑底面以下有深层软土需将墙体插入很深
的情况。因此，在地下工程中得到广泛应用，并且随着技术的进展和施工方法及机械的改进，地下连续墙进展到既是基坑施工时的挡墙围护结构，又能作为拟建主体结构的侧墙，也可采纳逆作法施工减少对环境和地面交通的影响。
3、柱列式灌注桩排桩支护
柱列式间隔布置包括：桩与桩之间有一定的净距的疏排布置形式和桩与桩相切的密排布置形式。为降低工程造价和施工便利，柱列式灌注桩作为挡土围护结构有很好的刚度，但各桩之间的连系差，一定在桩顶浇筑较大截面的钢筋混凝土帽梁加以可靠连结。为防止地下水并夹带土体颗粒从桩间空隙流入坑内，应同时在桩间或桩背采纳高压注浆、设置深层搅拌桩、旋喷桩等措施，或在桩后专门构筑防水帷幕。灌注桩施工时无振动，对周围邻近建筑物、道路和地下管线影响危害比较少。具有一定的优越性，但缺点是桩的施工速度较慢，且场地泥浆处理较困难，工期长。
4、内支撑和锚杆
作为基坑围护结构墙体的支承，内支撑和锚杆的作用对保证基坑稳定和控制周围地层变形极为重要。目前支护结构的内支撑，常用的有钢结构支撑和钢筋混凝土结构支撑两类，钢结构支撑多用圆钢管和大规格的型钢。为减少挡墙的变形，用钢结构支撑时可用液压千斤顶施加预应力。钢筋混凝土支撑是近几年在上海地区等深基坑施工中进展起来的一种支撑形式，它多用土模或模板随着挖土逐层现浇，
截面尺寸和配筋根据支撑布置和杆件内力大小而定，它刚度大，变形小，能有力的控制挡墙变形和周围地面的变形，宜用于较深基坑或周围环境要求较高的地区。
5、土钉墙支护
土钉墙围护结构是边开挖基坑，边在土坡面上铺设钢筋网，并通过喷射混凝土形成混凝土面板，从而形成加筋土重力式挡墙起到挡土作用。适用于地下水位以上或人工降水后的粘性土、粉土、杂填土，不适用于淤泥质及地下水位下且未经降水处理的土层，周围管线密集的基坑也应慎用。
6、深层搅拌水泥土桩支护青年在选择职业时的考虑
深层搅拌水泥土桩是用特制的进入土深层的深层搅拌机将喷出的水泥浆固化剂与地基土进行原位强制拌合制成水泥土桩，相互搭接，硬化后即形成具有一定强度的壁状挡墙既可挡土又可形成隔水帷幕，对于平面呈任何形状、开挖深度不很深的基坑，皆可用作支护结构，比较经济。
7、旋喷桩帷幕墙支护
它是钻孔后将钻杆从地基土深处逐渐上提，同时利用插入钻杆端部的旋转喷嘴，将水泥浆固化剂喷入地基土中形成水泥土桩，桩体相连形成帷幕墙，可用作支护结构挡墙。在较狭窄地区亦可施工。它与深层搅拌水泥土桩一样是重力式挡土墙，只是形成水泥土桩的工艺不同。
三、支护结构计算方法
现有的基坑支护结构的内力变形计算的方法很多，如静力平衡法、等值梁法、连续介质有限元法以及弹性地基杆系有限元法等等。静力平衡法是最常用的方法，其要点是选择一定的入土深度以满足整体稳定，抗隆起和抗渗要求的前提下用经典土力学理论计算主动土压力和被动土压力，然后对重力式刚性挡墙验算其抗倾覆、抗滑移稳定性，安全系数沿用设计规范中对平常挡土墙的规定；或者计算柔性挡墙的内力，对墙身和支锚结构进行设计。这种方法对于平常挡土墙或开挖深度不深的钢板桩是比较成熟的。但对深基坑，格外是软土中的深基坑支护结构设计就难以考虑更为复杂的条件和难以分析支护结构的整体性状。等值梁法把围护结构简化成两根梁进行计算，虽然不能准确计算围护结构的位移，是典型的强度控制设计方法，但由于其计算简洁，在单支撑的基坑工程中仍然用到这一方法，随着计算机的普及，有限元兼有广泛通用性和灵活性，可模拟复杂的施工过程，成为一种很有前途的基坑设计计算方法，但目前连续介质有限元法由于土的本构关系尚在进展中，缺乏真实反映土的应力应变关系的本构模型，以及计算参数难以准确确定，也不能准确计算出支护结构及土体的位移，目前还没有得到广泛的应用。杆系有限元法作为一种计算方法具有概念清楚，计算简洁，计算参数较少，受到基坑工程设计人员的青睐。但现有的杆系有限元法的计算参数的取值因为众多复杂因素的影响尚没有较好的计算方法，取值多凭设计者本人的经验，因而计算结果与实际差别较大，计算结果不稳定且精度很低，不能满足对变形要求严格的、大型复杂的基坑工程的设计要求。总之，现有的基坑工程设计方法均是从爱护基坑工程的稳定出发，属于强度控制设计范畴。
四、深基坑技术未来的进展
1、基坑向着大深度、大面积方向进展，周边环境更加复杂，深基坑开挖与支护的难度愈来愈大。因此，从工期和造价的角度看两墙合一的逆作法将是今后进展的主要方向。但逆作法施工受桩承载力的限制很大，采纳逆作法时不能采纳一柱一桩，而是一柱多桩，增加了成本和施工难度。如何提高单桩承载力，降低沉降，减少中间支承柱，达到一柱一桩，使上部结构施工速度可以e网打尽
放开限制，从而加快进度，缩短总工期，这将成为今后的研究方向。
2、土钉支护方案的大量实施，使得喷射混凝土技术得以充分运用和进展。为减少喷射混凝土的回弹量以及爱护环境的需要，湿式喷射混凝土将逐步取代干式喷射混凝土。
析构3、目前，在有支护的深基坑工程中，基坑开挖大多以人工挖土为主，效率不高，今后一定大力研究开发小型、灵活、专用的地下挖土机械，以提高工效，加快施工进度，减少时间效应的影响。
承德师专4、为了减少基坑变形，通过施加预应力的方法控制变形将逐步被推广，另外采纳深层搅拌或注浆技术对基坑底部或被动区土体进行加固，也将成为控制变形的有效手段被推广。
5、为减小基坑工程带来的环境效应（如因降水引起的地面附加沉降），或出于爱护地下水资源的需要，有时基坑采纳帷幕型式进行支护。除地下连续墙外，一般采纳旋喷桩或深层搅拌桩等工法构筑成
止水帷幕。目前，有将水利工程中防渗墙的工法引入到基坑工程中的趋势。
6、在软土地区，为幸免基坑底部隆起，造成支护结构水平位移加大和邻近建筑物下沉，可采纳深层搅拌桩或注浆技术对基坑底部土体进行加固，即提高支护结构被动区土体的强度的方法。
外文原文
Along with the increase of the high-rise building, according to the structure and the application requirements, basic buried depth also always increase, so there appear a large number of deep foundation pit engineering, and the city of foundation pit engineering houses and are often the lifeline project dense area, many cases not allowed by the comparative economic put slope excavation, and need in artificial support under conditions of foundation pit excavation, in order to guarantee the foundation pit of buildings, underground pipeline, road safety, we should promote the deep foundation pit supporting technology.
A.deep foundation pit engineering, the main content
First, geotechnical engineering and engineering survey. Sure geotechnical parameter and groundwater parameters; Determination of adjacent building around, things, urban road buried under
ground engineering services such as the current situation, and the formation of the limits with displacement to analysis.
Second, supporting structure design. Including the retaining wall palisade structure (such as continuous wall, column type filling pile retaining wall), supporting system (such as interior support, anchor) and soil consolidation, etc. The design of the support structure must be and foundation pit
construction proposal closely, need to consider primarily on local experience, soil and groundwater situation, environmental safety around allowed by the stratum deformation limits, may provide the construction of facilities and construction site, construction period and cost etc.
Third, and foundation pit excavation and supporting of construction. Including earthworks, engineering precipitation and the organization of construction engineering design and implementation.
Forth, formation displacement prediction and the surrounding engineering protection. It depends on the soil formation displacement and the supporting structure performance and groundwater changes, also depends on the construction process and construction process. If more than the allowable value of the deformation forecast, shall be modified supporting structure design and construction scheme a
nd, when necessary, the important engineering facilities to the neighboring take special protection or reinforcement measures.
Fifth, construction site measurement and monitoring. According to the monitoring data and information and, when necessary, feedback design, use the information to guide the next step of the construction.
滚子链联轴器B. deep foundation pit supporting structure types
First,steel sheet pile support
Steel sheet pile used in the construction of the deep foundation pit supporting, is a kind of simple construction, investment economic support method. In soft soil area of Shanghai used more often in the past, but because the steel sheet pile itself flexible big, such as support or anchor pull system not set properly, its deformation will be very big. So the foundation pit supporting a depth of more than 7 m soft soil layer, unfavorable use steel sheet pile foundation pit supporting, unless set multi-level support or anchor bars, but should consider to the basement construction steel sheet pile after pulling out of the foundation and ground surface deformation around the influence.
Second, underground continuous wall
Underground continuous wall is in slurry supporting conditions points slot of the reinforced concrete building walls, underground continuous wall first began in 1950 used in Paris and milan city underground construction projects. Because of underground continuous wall has overall rigidity and the antiseepage, suitable for in the underground water level of soft clay and sand soil under various stratum condition and complex construction environment, especially the deep foundation pit bottom have soft soil should be inserted into the wall very deep.Therefore, in underground engineering extensively, and with the development of technology and construction methods and machinery of improvement, underground continuous wall to development is in construction of foundation pit retaining wall enclosure structure, and can be used as the main structure of the proposed side wall, also can use top down construction to the environment and to reduce the influence of ground traffic.
Third, column type filling pile row pile support
Column type interval layout including: between piles have certain interval of drain line layout and piles and piles of tangent densely decorate a form. In order to reduce the construction cost and the construction is convenient, column type filling pile as soil retaining palisade structure have very good rigidity, but each pile is not between the poor, must be large pile top casting of the reinforced concrete beam section cap to reliable links.To prevent the groundwater and soil entrainment from bet
ween pile particles into space in the pit, should be at the same time in the pile or the high pressure grouting pile back, set deep mixing pile, jet grouting pile and other measures, or in special building waterproof curtain
after pile. When filling pile construction no vibration, on the surrounding adjacent building, roads and underground pipeline effect less harm. Has certain advantages, but its weakness is that the pile construction speed is slow, and the mud treatment more difficult, long time limit.
Forth, interior support and anchor
As a pit enclosure structure wall of supporting, supporting and anchor role in ensuring foundation pit draw stability and control of strata deformation around is very important. At present the supporting structure in support, commonly used in steel structure to support and reinforced concrete structure to support two kinds, steel structure to support multi-purpose circular steel tubes and big specifications of steel. In order to reduce the deformation of the retaining wall, with steel structure to support can be used when hydraulic jack prestress.Reinforced concrete support is in recent years in Shanghai area deep foundation pit construction such as the developed a kind of support form, more than it would die or template with digging cast-in-situ step by step, section size and reinforcement accordin
g to support arrangement and stem a internal force size and decide, it rigidity deformation is small, can effectively control the retaining wall deformation and the deformation of the surrounding the ground, appropriate is used for deep foundation pit or the surrounding environment to demand higher area.
Fifth, soil nailing wall
The soil nailed wall palisade structure is the foundation pit excavation, the side slope surface laid in reinforcement fabric, and through the jet concrete form concrete panel, so as to form the reinforced soil retaining a gravity retaining wall role. Application to underground water level or above or artificial precipitation of the cohesive soil, powder soil, miscellaneous fill in the soil, does not apply to the muddy and underground water level and precipitation processing under without the soil layer, around the foundation pit should also dense pipeline carefully use.
Sixth, deep mixing cement pile support
Deep mixing cement pile is with special go into the deep deep mixer will the jet of water mud curing agent and foundation soils in situ made mandatory white cement pile, mutual lap, hardening is formed namely after a certain intensity of the retaining wall wall can not only soil retaining and can fo
rm the water curtain, in regard to MianCheng any shape, excavation depth not deep foundation pit, all can be used for supporting structure, more economic.
Seventh, jet grouting pile curtain wall supporting
It is bored after will drill pipe from deep foundation soil on carry gradually, at the same time use at the end of the pipe into the rotation of the nozzle, curing agent injected water will be the foundation soil formed in cement pile, the pile formed connected on the curtain wall, can be used for supporting retaining structure. In a narrow area can be construction. It and deep mixing cement pile, is gravity retaining wall, just form cement pile of different technology.
C.supporting structure calculation method
The existing foundation pit supporting structure of the internal force redistribution of the deformation calculation method many, such as static balance method, equivalent beam method and finite element method for medium and elastic foundation rod finite element method and so on. The static balance method is the most commonly used method, the key is to choose a certain fields to meet the overall stability depth, resistance to uplift and anti-permeability the precondition of soil mechanics theory calculation with classic active earth pressure and passive earth pressure, and then the gravity
retaining wall rigidity check its resistive overturning, resistance to slip stability, safety coefficient continue to
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