Analysis And Application Of Differential Settlement Of Main Podium On Strongly Weathered Rock Foundation

With the increasing demand for diversification of building functions,the arrangement of low podiums on one or both sides of high-rise buildings has gradually become the mainstream of urban construction development.The difference in structural loads between high-rise buildings and low-rise podiums can lead to uneven settlement problems,which can further cause structural cracking and many other problems.At present,the engineering field often uses the post-pouring zone of settlement to solve the above problems,although the method can better solve the main podium differential settlement problem,but there are still many disadvantages,such as delay,increase construction costs,settlement back pouring at the quality control is difficult.The geological conditions in Qingdao are mostly rocky and the foundation conditions are good.There are many successful cases of cancelling or closing the post-pouring zone of settlement in advance,but in practice the majority of projects still widely use the settlement backcasting zone method.Therefore,this paper combines the local geological conditions of Qingdao with engineering statistics,field settlement measurements and finite element analysis,and conducts research around the differential settlement law of the main podium on strongly weathered rock foundations to provide reference for the cancellation or early closure of the main podium structure under the relevant foundation conditions of the settlement post-cast zone,as follows:(1)The current status of domestic and international research on post-pouring zone of settlement is summarised,and the requirements of the relevant codes and standards on the limit value of differential settlement of the main podium and the regulations on the setting of settlement setback zones are summarised.The actual cases of projects in Qingdao where no settlement belts were set under strong weathered rock foundation conditions and the corresponding settlement data or effects were collected and collated,providing a factual basis for the cancellation or early closure of settlement belts in similar projects in the future.(2)On-site settlement observations were carried out for a project under strongly weathered rock foundation conditions in the Qingdao area.In view of the constraints of the site conditions,the general settlement observation often has 2-3 layers missing in the first stage,this paper proposes a supplementary method based on the settlement theory and development law,the actual measured settlement data to approximate the missing data in the first stage to derive the calculation,in order to obtain the settlement curve of the whole construction process.On this basis,the development of settlement changes in the main building and the podium during construction,as well as the settlement difference between the maximum settlement points of the main podium and the settlement difference on both sides of the post-pouring zone of settlement with the construction progress are analysed using the project as a case study.(3)Based on ABAQUS finite element software,a series of structural models of the main podium were established to study the influence of factors such as the height of the main building and the podium,foundation conditions and the location of the podium plan distribution on the settlement differences and foundation tensile stresses in the main podium,and to arrive at a recommendation on the height of the main podium that can eliminate the settlement back-cast zone.The paper proposes a method to simulate the settling zone based on life and death units,which can realise the efficient simulation of settling zone retention and early closure,and based on this,analyses the proposed height of the main podium that can be closed in advance.