薛明智深基坑土釘支護設計與施工應用.rar

深基坑土釘支護施工應用
                                         
孫春煥  顧明春  薛明智

土釘支護是深基坑開挖護坡普遍采用的一項新技術，其工藝及技術原理是：土釘一端與維護墻體連接，另一端通過螺旋鉆機或人工洛陽鏟在土層內成孔，土釘居中埋入孔內，灌注M10以上水泥砂漿或純水泥砂漿，使“土釘—水泥”形成小圓柱體錨固在土內，增強邊坡抗滑穩定能力，改善土體破壞的延塑性。通常，土釘采用Ⅱ、Ⅲ級鋼筋，直徑宜為16－32mm；錨孔鉆孔直徑宜為70－120mm；圍護墻面采用鋼筋掛網，噴射C20強度以上細石混凝土，厚度不小于80mm。
對照《規范》（JGJ120-99）中單根土釘受拉荷載標準值Tjk=ζeajksxjszj/cosαj，及單根土釘抗拉承載力設計值Tuj=（1/γs）πdnj∑qsikli公式中的因子分析，土釘護坡及土釘抗拔能力與以下幾方面有關，施工中可以作為技術、質量預控的關鍵點：①邊坡坡度（β），②土釘水平、垂直間距（sxj, szj）,③土釘安置傾角（αj）；④土釘成孔直徑（dnj）;⑤土釘有效錨固長度（li）;⑥土層狀態（土的內摩擦角φ，液性指數IＬ，孔隙比）。
隨著土釘支護技術的發展，在一些情況下，為了控制邊坡的側向變形和地表沉降，采用“土釘——預應力錨桿”聯合支護的形式，稱為復合土釘墻
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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