深大基坑中冠梁的变形特征及一种新型冠梁

DEFORMATION CHARACTERISTICS OF CONVENTIONAL AND NEW TOP BEAMS IN DEEP AND LARGE FOUNDATION PIT WITH NUMERICAL SIMULATIONS

基坑尺寸影响其支护结构的变形特征,在大尺寸基坑中,长冠梁的作用并不十分明晰。为探究其受力、变形形式及对其他支护结构的影响,在前人研究基础上对大、小尺寸基坑的冠梁荷载条件及约束条件进行了研究,得出了长、短冠梁的基本变形特征;通过数值法验证了长冠梁的变形特性,并对冠梁完整性、锚杆预应力的设置效果等进行了评价;通过总结长冠梁支护效果的优劣点,提出了一种拼接式的新型冠梁,利用数值法对其支护效果、抗破坏扩展性进行了评价。研究表明:长冠梁比短冠梁有更完整的“波形特征”,该特征可能恶化局部排桩的稳定条件、阻碍预应力锚杆发挥作用,提出的新型冠梁通过先铰接、再刚接的方式,在减小变形、提高锚杆支护效力的基础上,保留了传统冠梁加强支护结构整体性的作用,是一种优化设计。

The size of the foundation pit affects the deformation characteristics of its supporting structure.The effect of long top beams in a long foundation pit is not quite clear.In order to clarify the force state,deformation form and the influence on other supporting structures,we studied the load conditions and restraint conditions of long and short top beams on the basis of previous studies,and obtained their main deformation characteristics.With the help of numerical simulation,we verified the long top beam s deformation form,and assessed effect of different level of integrity and the setting of prestress on the anchor rod.Then we proposed a new spliced top beam,based on the advantages and disadvantages of traditional top beam.Then we assessed its supporting effect and restrict ability on damage expansion by numerical methods.Study shows that the long top beams have more complete“wave characteristics”than the short top beams,which may deteriorate the stability conditions of local piles and hinder the function of prestressed anchors.The proposed new top beams are hinged and then rigidly connected,which weakens the“wave characteristics”.It retains the function of the traditional top beam to strengthen the support structure and reduces the deformation and improves the effectiveness of bolt support.It turns out to be an optimized design.