薛明智深基坑土钉支护设计与施工应用.rar

深基坑土钉支护施工应用
                                         
孙春焕  顾明春  薛明智

土钉支护是深基坑开挖护坡普遍采用的一项新技术，其工艺及技术原理是：土钉一端与维护墙体连接，另一端通过螺旋钻机或人工洛阳铲在土层内成孔，土钉居中埋入孔内，灌注M10以上水泥砂浆或纯水泥砂浆，使“土钉—水泥”形成小圆柱体锚固在土内，增强边坡抗滑稳定能力，改善土体破坏的延塑性。通常，土钉采用Ⅱ、Ⅲ级钢筋，直径宜为16－32mm；锚孔钻孔直径宜为70－120mm；围护墙面采用钢筋挂网，喷射C20强度以上细石混凝土，厚度不小于80mm。
对照《规范》（JGJ120-99）中单根土钉受拉荷载标准值Tjk=ζeajksxjszj/cosαj，及单根土钉抗拉承载力设计值Tuj=（1/γs）πdnj∑qsikli公式中的因子分析，土钉护坡及土钉抗拔能力与以下几方面有关，施工中可以作为技术、质量预控的关键点：①边坡坡度（β），②土钉水平、垂直间距（sxj, szj）,③土钉安置倾角（αj）；④土钉成孔直径（dnj）;⑤土钉有效锚固长度（li）;⑥土层状态（土的内摩擦角φ，液性指数IＬ，孔隙比）。
随着土钉支护技术的发展，在一些情况下，为了控制边坡的侧向变形和地表沉降，采用“土钉——预应力锚杆”联合支护的形式，称为复合土钉墙
Deep Foundation Construction Application of soil nailing
                                          
Sun Chunhuan Guming Chun Xue Mingzhi

Soil nailing are deep excavation slope commonly used for a new technology, process and technical principles are: one end and maintenance of soil-nail wall Lian Jie, Ling Yi side Tongguo spiral drill or artificial soil Nei Luoyang shovel into the hole Zai , buried in the middle nail hole, more than perfusion M10 mortar or pure cement mortar so that the "soil nails - cement" to form a small cylinder anchored in the soil, the enhanced capacity of side slope stability, improve the soil failure ductility . Typically, the soil nails used Ⅱ, Ⅲ grade steel, diameter appropriate for the 16-32mm; anchor hole diameter appropriate for the 70-120mm; retaining wall hanging by steel mesh, spray more than C20 fine aggregate concrete strength, thickness of not less than 80mm.
Control "standard" (JGJ120-99) in a single nail the standard value of tension force Tjk = ζeajksxjszj / cosαj, and soil nail tensile capacity of a single design value of Tuj = (1/γs) πdnjΣqsikli formula factor analysis of soil nails and nail slope uplift capacity with the following aspects related to construction as technology, quality pre-control of key points: ① slope gradient (β), ② nail horizontal and vertical spacing (sxj, szj) , ③ nail placement angle (αj); ④ nail hole diameter (dnj); ⑤ effective anchorage length of the nail (li); ⑥ soil state (soil internal friction angle φ, liquidity index IL, void ratio) .
With the soil nailing technology, in some cases, in order to control the slope of the lateral deformation and surface settlement, a "soil nails - Anchor" in the form of combined support, known as the composite soil nailing walls
 

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