基坑支护外文文献

.中文3700字Soil nail wall, also known as soil nailing technology, which is installed in situ soil with a relatively dense soil nails, and soil slope surface of sprayed concrete to build a steel mesh surface layer, through the soil nails, the surface layer and in-situ soil the role of the three common slope or retaining wall side. Soil nail walls but also poses a similar gravity in situ reinforced earth retaining structures. And supporting a variety of methods have been compared, it has the construction easy, simple equipment, require little space, excavation and supporting jobs can be parallel, the overall progress of the fast, low cost, as well as pollution, low noise, stable and reliable, social and economic good, and many other advantages, and therefore at home and abroad with the foundation pit slope reinforcement has been widely applied rapidly. Soil nail wall construction technology is a top-down step by step build process, according to the following order: According to design requirements for excavation face, trimmed slope, planted sprayed concrete thickness control signs; jet first layer of concrete; erection of drilling soil nails, grouting, erection of connectors; banding steel net, spray a second layer of concrete; set top of the hill, slope and the foot of the slope of the drainage system. Soil-nailed law-enforcement: keep as much as possible, significantly higher maximum use of pit wall side of inherent mechanical strength of soil, changing soil structure and system load as part of the bracing. Sprayed concrete under the effect of high pressure gas flow, wherein high-speed soil surface layer and the soil in the spray created between embedded solid-effect, and gradually form a completely closed with the excavation shoring systems, spray layer and mounted with a protective layer of and reinforcement of topsoil, so that to avoid exposure to wind and rain erosion, shallow collapse, local spalling, as well as the role of impermeable impermeable. Soil nailing a special control pressure grouting can be reinforced medium greatly improved physical and mechanical properties make it become a new geological body, its solid-solid in the slip plane the deep section of the soil outside the house, its external fixed terminal Spray the surface layer in conjunction with the network as a whole may be a tendency to instability in the side wall transferred to the solid-section and its vicinity and to eliminate. Reinforced Mesh sprayed layer can have a better integrity and flexibility, can effectively adjust the spray layer and the stress distribution within the soil nail. Active soil nail retaining soil and with soil together with construction of simple, rapid and timely, flexible applicability, with the digging with sticks, safe and economic characteristics. Its duration is generally poorer than the traditional method to save more than 30-60d, engineering, low cost and 10% -30%, supporting the maximum vertical pit depth has now reached 21.5m, built mud (local miscellaneous fill) pit depth of 10m. This method not only effectively be used for general geotechnical deep excavation shoring, often also used a number of other ancillary support measures, can effectively be used for supporting streaming sand, silt, complex filling, saturated soil, soft soil, etc. adverse geological conditions of the deep excavation. In addition, it is also rapid, reliable and economical method of using the traditional method or improved facilities to be made or have been carried out rescue excavation instability reinforcement. Of soil nailing and reinforced soil and anchor it seems such as retaining structures, however, the structure of soil nailing and reinforced earth construction, etc. There are many different points, and anchor. First of all, soil nailing and reinforced soil slope or retaining wall is not the same, mainly reflected in: the construction in different ways. Soil-nailed construction of the distribution of expansion from top to bottom, side excavation while retaining full use of undisturbed soil strength. Reinforced earth structure from bottom to top filling layered construction, filling choice, density and intensity can be controlled; reinforced pull the biggest changes in body pattern is different. In the reinforced earth structure, the general body at the bottom of the tendon force maximum. In the structure of soil nailing, the general range of the central part of the largest force of soil nail, the upper and bottom of the soil nail force small; different deformation properties. Soil Nailing the maximum displacement occurred in the supporting slope at the top or near the top, reinforced earth structure, the maximum displacement at the bottom. Secondly, soil nailing and bolting or retaining wall is not the same, mainly due to: the various parts of the force and the same role. Bolting or retaining wall of the anchor generally anchorage section and free above, the use of sliding surface to provide resistance outside the anchorage section, set the anchor generally prestressed, the free section under uniform tension effect, through the anchor seat passed to the slope of the retaining structures, earth retaining structures greater stiffness, mainly through the provision of resistance by the moment, is one of the main force components. Soil nailing settings generally do not impose pre-tension, but occurs in the soil after a small deformation of the passive force, the size of the force along the uneven distribution of soil nail extension, the middle on both sides of the small, the role of the force at the surface layer than the small, sprayed concrete surface layer is not a major force components, its role is to stabilize the surface of the partial excavation of soil to prevent caving and erosion; setting different densities. In the bolt support in the unit area on the retaining bolt set the number of generally less, for each root anchor construction accuracy and requirements are very stringent. In the soil-nailing, the surface of soil nail retaining a little bit more dense arrangement of individual soil nail construction relatively low accuracy and quality requirements; design of different lengths. In the bolt support, the design requirements must meet the requirements of each root anchor of resistance, so bolt anchorage section require in-depth into the stable layer, the design of a longer length. In soil nailing, the more dense arrangement of soil nail, the large number of interaction with the surrounding soil, to maintain self-reinforced zone of soil stability, and resistance to outside the region reinforced the role of soil pressure, design shorter length. Of course, there are many types of bolts, there are not pre-stressed, the length than the average soil-nail even shorter, but this bolt is mainly used for the tunnel or underground works of the spray-anchor on the length than the average soil-nail is also is shorter, often only 2-4m. （1）Construction of Soil Nail Soil nailing is a soil-nail as a major component of the slope of the force supporting technology, which consists of dense soil nail group, has been reinforced in situ soil, sprayed concrete surface layer and the necessary water system components. （2）Structural Materials Steel: steel types, models and sizes should be consistent with design requirements, should adopt the H-or H-class steel workers, reinforced after the purchase should be properly safeguarded to prevent corrosion, production should be transferred straight, rust, oil removal, should be carried out physical and mechanical properties or chemical composition analysis of test welding of steel, should be weldability and welding quality of the test for detection of welding material strength should be greater than the overall strength; Cement: ordinary portland cement used, label P032.5, if necessary, sulfuric acid resistant cement, alumina cement should not be used. Cement should comply with the provisions of the existing cement standard requirements, there must be a single factory test reports, quality inspection orders, factory card documents, in accordance with its varieties, label, test numbers etc., and inspection and acceptance sampling inspection, by the examination results are reasonableUse. Bags of cement should be properly kept in storage and transportation, rain, moisture, stacked in a certain height from the ground heap shelves, is strictly prohibited and damage throwing throwing bags, prohibited the use of damp or different varieties of mixed cement label. Aggregate: stone and sand material (seeds film, medium-fine sand) should check report cards, the stone test methods and quality standards by JGJ53-92, sand material testing methods and quality standards by JGJ52-92. Particle size of less than 2mm in the sand, sand, clay content by weight not more than 3%, the particle size of less than 12mm gravel or melon tablets, clay content by weight not more than 3%. Mixing of water: the water without affecting the normal condensation of cement hardening of harmful impurities, may not contain fat, sugar and free acid, etc.; water, PH value is less than four of acidic water and sulfur ion of more than 1% of the water weight of water were shall not be used; the use of tap water or clean water for mixing natural water could be dispensed with for testing. Quick-setting agent: quick-setting agent is used in J85, 711, or Red Star 1, should be specifically responsible for control, add the weight of 3% of the weight of cement, the machine automatically added by the jet. Electrodes: The THJ422. Concrete mix: In addition to spraying the concrete mix design standards to be attained strength, we must also meet the technical requirements of construction, with the ratio of 1:0.4:2:2 (cement: water: sand: melon pieces), melon seeds piece maximum diameter of not more than 12mm. Grouting mixture ratio: one-grouting with cement mortar 1:1, the second grouting using water-cement ratio of 0.5 water slurry, cement mortar and cement slurry must be stirred evenly pure, a mixing of the slurry must be initial setting before ( generally 2h) run out. Early strength and water-reducing agent: According to the nature of projects, using different types of early strength agent, commonly used red star on the 4th, 3F, NC, NNOF, NS2-1 and so on. （3）Net production of soil nailing and reinforced Size allowable deviation of soil nail making: the length of ?100mm, curved reposted elsewhere in the paper for free download http:/www.hi138.com （4）Drainage System Soil Nailing appropriate to remove ground water under the conditions of construction, the drainage should take appropriate measures, including surface drainage, internal drainage, as well as supporting the drainage pit in order to avoid saturation of the soil and reduce the role of the hydrostatic layer on the surface pressure. Excavation around the bracing should be added within the surface finishing, and building drains and cement mortar or concrete surface to the underground water surface infiltration of precipitation. Pit top of the hill near the 2-4m wide and the ground should be properly boosted, and the inside of high external low, easy to run-off away from the slope. In supporting the back surface layer should be inserted in a length of 400-600mm, diameter of not less than the standard 40mm drain out its external side supporting surface layer spacing for 1.5-2m, in order to spray the plot after the surface layer of concrete water discharge. To rule out the accumulated water seepage inside the pit and rain should be set 300mm * 300mm Bottom drains, leads to the 600mm * 600mm * 600mm sump. Drains, leave the side wall 0.5-1m, drains and sump is appropriate to brick and mortar Plastering used to prevent leakage, pit water should be out in time. Mechanism of composite soil nail force.In the soil nailing system, the soil nail is an important force components, the role of soil nail will act on the surface layer or soil-cement pile on the water, soil pressure, soil nail and soil through the mill passed to the stability of the resistance Formation to go, similar to the soil anchor; through the dense and the soil nails will be a short retaining body deformation Houtu bound together to form from the soil, grouting and soil nailing body a composite soil, composite soil similar to the on the force of gravity dam. This role is similar to reinforced earth retaining pit; no matter what form of construction of soil nail (hole-drilling method, and entering the law and the roof into the law), soil nailing channels are grouting holes, which not only formed a soil grouting nail retaining wall and the formation of friction between the belt, at the same time in order to split, penetration and compaction grouting in the form of reinforced retaining Houtu body, such a role similar to the mechanism of compaction grouting. The process of soil nail force Measurements showed that the process of soil nail force can be divided into three stages: Phase I: soil nail installed an early stage, but the completion of grouting grouting of the bonding between the body and the soil has not been formed, when the soil nail largely unaffected by power. Phase II: grouting body of the soil nail bonding in the formation, with the excavation depth increases, soil nailing has the effect of tension, and tension concentrated in the surface layer bonded with the site, then internal force distribution is similar to non - Free-form deformation of the soil anchor segment near the surface layer at the biggest rally, the subsequent decrease gradually. The third phase: excavation of sufficient depth, soil nailing most of the slip at the range. At this time the performance of soil nailing for the middle of internal force (near the slip surface) the largest and the smallest at both ends. Force distribution is similar to reinforced earth retaining wall in the stretch. 土钉墙又称为土钉支护技术，它是在原位土中敷设较为密集的土钉，并在土边坡表面构筑钢丝网喷射混凝土面层，通过土钉、面层和原位土体三者的共同作用而支护边坡或边壁。土钉墙体同时也构成了一个就地加固的类似重力式挡土结构。与已有的各种支护方法相比，它具有施工容易、设备简单、需要场地小，开挖与支护作业可以并行、总体进度快、成本低，以及无污染、噪声小、稳定可靠、社会效益与经济效益好等许多优点，因而在国内外的边坡加固与基坑支护中得到了广泛迅速的应用。土钉墙的施工技术是一种由上而下分步修建的过程，可按下列顺序进行:按设计要求开挖工作面，修整边坡，埋设喷射混凝土厚度控制标志;喷射第一层混凝土;钻孔安设土钉、注浆、安设连接件;绑扎钢筋网，喷射第二层混凝土;设置坡顶、坡面和坡脚的排水系统。土钉支护法:以尽可能保持、显著提高、最大限度地利用基坑边壁土体固有力学强度，变土体荷载为支护结构体系一部分。喷射混凝土在高压气流的作用下高速喷向土层表面，在喷层与土层间产生“嵌固效应”，并随开挖逐步形成全封闭支护系统，喷层与嵌固层同具有保护和加固表层土，使之避免风化和雨水冲刷、浅层坍塌、局部剥落，以及隔水防渗作用。土钉的特殊控压注浆可使被加固介质物理力学性能大为改善并使之成为一种新地质体，其内固段深固于滑移面之外的土体内部，其外固端同喷网面层联为一体，可把边壁不稳定的倾向转移到内固段及其附近并消除。钢筋网可使喷层具有更好的整体性和柔性，能有效地调整喷层与土钉内应力分布。土钉主动支护土体并与土体共同作用，具有施工简便、快速及时，机动灵活、适用性强、随挖随支、安全经济等特点。其工期一般比传统法节省30-60d以上，工程造价低10%-30%，支护最大垂直坑深目前已达到21.5m，建成淤泥(局部杂填土)基坑深达10m。该方法不仅能有效地用于一般岩土深基坑工程支护，而且通常还采用一些其他辅助支护措施，能有效地用于支护流砂、淤泥、复杂填土、饱和土、软土等不良地质条件下的深基坑。此外，它还能快速、可靠、经济地对采用传统法或改良法施作的将要或已经失稳的基坑进行抢险加固处理。土钉支护似乎与加筋土和锚杆等挡土结构一样，然而土钉支护在结构施工等方面与加筋土和锚杆有许多不同点。首先，土钉支护与加筋土边坡或挡墙不相同，主要表现在:施工方法不同。土钉支扩从上到下分布进行修建，边开挖边支护，充分利用原状土的强度。加筋土结构由下到上分层填土构筑，填料可以选择，密实度和强度可以控制;加筋体最大拉力的变化规律不同。在加筋土结构中，一般处于下部的筋体受力最大。在土钉支护结构中，一般介于中部的土钉受力最大，上部和底部的土钉受力较小;变形性能不同。土钉支护最大位移发生在支护边坡顶部或接近顶部，加筋土结构的最大位移在底部。其次，土钉支护与锚杆支护或挡墙也不相同，主要在于:各部分的受力和作用不同。锚杆支护或挡墙中的锚杆一般都有锚固段和自由段，利用滑动面以外的锚固段提供抗力，设置锚杆一般要施加预应力，自由段受到均匀的拉力作用，通过锚座传递到坡面的挡土构件上，挡土构件的刚度较大，主要通过受弯矩提供抗力，是主要的受力部件之一。土钉设置后一般不施加预拉力，只是在土体发生微小变形后才被动受力，受力的大小沿土钉延长的分布不均匀，中间大两边小，所作用在面层上的力较小，喷射混凝土面层不是主要受力部件，其作用是稳定开挖面上的局部土体，防止崩落和受到侵蚀;设置密度不同。在锚杆支护中，单位支护面积上设置的锚杆数量通常较少，对每根锚杆的施工精度和要求都十分严格。在土钉支护中，支护面上土钉排列得较密，对单个土钉的施工精度和质量要求相对较低;设计长度不同。在锚杆支护中，设计要求每根锚杆都要达到要求的抗力，所以锚杆的锚固段需要深入到稳定的土层中，设计长度较长。在土钉支护中，土钉排列较密，数量众多，与周围土层共同作用，能够保持加固区土体的自身的稳定，并抵抗加固区以外的土压力的作用，设计长度较短。当然，锚杆有许多种类，也有不加预应力、长度比一般的土钉还要短，但这种锚杆主要用于隧道或地下工程的喷锚支护上，长度比一般的土钉还要短，常用只有2-4m。（1）土钉墙结构组成土钉支护是以土钉作为主要受力构件的边坡支护技术，它由密集的土钉群、被加固的原位土体、喷射混凝土面层和必要的防水系统组成。（2）土钉墙结构材料钢材:钢筋的种类、型号及尺寸规格应符合设计要求，宜采用H级或工H级钢筋，钢筋购进后应妥善保管，防止锈蚀，制作时应调直、除锈、除油，应进行物理力学性能或化学成份分析试验，焊接用的钢材，应作可焊性和焊接质量的试验检测其焊接强度应大于材料整体强度;水泥:采用普通硅酸盐水泥，标号P032.5，必要时采用抗硫酸水泥，不得使用高铝水泥。水泥应符合现行水泥标准的规定要求，必须有制造厂的试验报告单、质量检验单、出厂证等证明文件，并按其品种、标号、试验编号等进行检查验收并取样检验，按检验结果合理使用。袋装水泥在储运时应妥善保管、防雨、防潮，堆放在距离地面一定高度的堆架上，严禁抛摔和损坏包装袋，严禁使用受潮或不同标号品种混杂的水泥。骨料:石料和砂料(瓜子片、中细砂)应有检验报告单，石料的检验方法和质量标准按JGJ53-92，砂料的检验方法和质量标准按JGJ52-92。粒径小于2mm的中砂，砂的含泥量按重量计不大于3%，粒径小于12mm碎石或瓜子片，含泥量按重量计不大于3%。拌合用水:水中不含有影响水泥正常凝结硬化的有害杂质，不得含油脂、糖类及游离酸等;污水、PH值小于4的酸性水和含硫酸根离子超过水重1%的水均不得使用;使用自来水或清洁的天然水作拌合用水，可免作试验。速凝剂:所用速凝剂为J85、711或红星1号，应有专人负责掌握，添加重量为水泥重量的3%，喷射时由机器自动添加。焊条:采用THJ422。混凝土配合比:喷射混凝土的配合比除应达到设计标准强度外，还应满足施工工艺要求，配合比为1:0.4:2:2(水泥:水:砂:瓜子片)，瓜子片的最大直径不大于12mm.注浆配合比:一次注浆采用1:1水泥砂浆，二次注浆采用水灰比为0.5的纯水泥浆，水泥砂浆与水泥纯浆必须搅拌均匀，一次拌和的浆必须在初凝前(一般为2h)用完。早强减水剂:根据工程性质，采用不同类型的早强剂，常用红星四号、3F、NC、NNOF、NS2-1等。（3）土钉及钢筋网制作土钉制作尺寸允许偏差:长度100mm，弯曲度钢筋制作要求:钢筋使用前应调直并清除污垢，钢筋网宜在喷射一层混凝土后铺设，钢筋与坡面的间隙不宜小于20mm，钢筋网宜采用绑扎，钢筋网与土钉应连接牢固，钢筋网外侧宜用加强筋固定在土钉上。 （4）排水系统土钉支护宜在排除地下水的条件下进行施工，应采取恰当的排水措施，包括地表排水、支护内部排水以及基坑排水，以避免土体处于饱和状态并减轻作用于面层上的静水压力。基坑四周支护范围内的地表应加修整，构筑排水沟和水泥砂浆或混凝土地面防水地表降水向地下渗透。靠近基坑坡顶宽2-4m的地面应适当垫高，并且里高外低，便于径流远离边坡。在支护面层背部应插入长度为400-600mm，直径不小于40mm的水平排水管，其外端伸出支护面层，间距可为1.5-2m，以便将喷射混凝土面层后的积水排出。为了排除积聚在基坑内的渗水和雨水，应在坑底设置300mm300mm排水沟，通至600mm600mm600mm集水坑。排水沟应离开边壁0.5-1m，排水沟及集水坑宜用砖砌并用砂浆抹面以防止渗漏，坑中积水应及时抽出。复合土钉受力机理。在土钉支护体系中，土钉是重要的受力构件，土钉的作用将作用于面层或水泥土桩上的水、土压力，通过土钉与土体的磨阻力传递到稳定的地层中去，类似于土层锚杆;通过密而短的土钉将支护后土体的变形约束起来，形成由土体、注浆体及土钉组成的复合土体，复合土体类似于重力式坝受力。这种作用类似于加筋土挡支护;不管用什么形式施工的土钉(钻孔法、打入法和顶入法)，土钉通道都是注浆孔，该注浆不仅形成了土钉挡墙与地层之间的摩擦带，同时以劈裂、渗透及压密注浆的形式加固了支护后土体，这种作用类似于压密注浆机理。土钉的受力过程根据量测表明，土钉的受力过程可分为三个阶段:第一阶段:土钉安设的初期，完成注浆但注浆体与土层之间的粘结尚未形成，这时该土钉基本不受力。第二阶段:注浆体将土钉粘结于地层中，随着开挖深度的增加，土钉逐渐产生拉力，并将拉力集中在与面层粘结的部位，这时内力分布类似于无自由变形段的土层锚杆靠近面层处拉力最大，往后逐渐减小。第三阶段:开挖足够深度，土钉的大部份处于滑裂范围之内。这时土钉内力表现为中间部位(近滑裂面)最大，两端最小。力的分布类似于加筋土挡墙中的拉筋。.