某基坑复合土钉墙土钉内力超限分析

土钉与预应力锚杆的联合支护在基坑工程中运用广泛,近年来的研究也取得很大进展,但对其受力情况及作用机理仍未完全认识,在实际工程中也有一些失败的教训。本文以内蒙古地区某产品煤槽仓工程为例,针对监测中土钉内力超预警值的情况,从共同作用机理及施工过程控制等方面对数据进行了分析。分析结果表明,未及时喷射混凝土面板致使土体由于缺乏表面约束产生塑性变形是造成土钉内力超限的主要原因,而在土体表面没有混凝土面板约束的情形下开挖过深并施加大的施工扰动更使得被监测的土钉内力值进一步加大。由此可见混凝土面板对于提高被开挖土体稳定性的作用十分明显,此外分析结果还表明了土体和支护结构之间存在时间及空间效应,在施工中应避免超挖和减少施工扰动。

Analysis on the Soil-Nail Axial Power Overburden of the composite Support Pattern of Soil Nails and Prestressed Anchors in the Deep Excavation

The composite support pattern of soil nails and prestressed anchors is used extensively in foundation. Its research made great progress in recent years. However, its function mechanism and forces have not been fully recognized. Failed cases were also seen in implementations. This paper is based on project of the large underground coal storage bin implementation of Inner Mongolia. With the soil-nail axial power overburden during monitoring, we analyzed the data based on the common mechanism and control of the project process etc. The results showed that the main reason of the soil-nail axial power overburden was not being able to spray concrete surface timely, causing soil mass plastic deformation due to lack of surface constraints. Deep excavation and large construction disturbance without concrete slab restraint imposed the axial press in the soil nail increase further. As a result, shooting concrete surface may increase the foundation safety obviously. In addition, force was influenced greatly by the excavation steps and time variation. Thus, during the excavation process, overbreak should be avoided and construction disturbance should be reduced.