Experimental Study On Secondary Consolidation Creep Characteristics Of Q₃ Loess In Tang Jiayuan Tunnel

Loess is widely distributed in the western part of China.Tunnels crossing the loess area,in addition to ensuring the stability of surrounding rock during excavation,are also required to resist deformation caused by long-term consolidation and creep.In the actual project,some loess tunnels are subject to excessive deformation and lining cracking due to secondary consolidation creep,which adversely affects the long-term stability of the structure.At the same time,many soils are not destroyed according to the theoretical strength theory,but in fact,after a long period of creep deformation,the damage is generated,indicating that the long-term strength of the soil decreases with time.Therefore,studying the secondary consolidation creep characteristics of loess and the long-term strength of the soil is of great significance to the design of the support of the tunnel and the determination of the safety factor of the soil.The main research results of the thesis are as follows:(1)In the secondary consolidation creep test,due to the lateral limitation of the ring cutter,the soil is difficult to be damaged,so soil creep parameters such as long-term strength are not obtained.This paper proposes a new test method.Based on the consolidation creep test,the possibility of obtaining creep parameters based on the secondary consolidation creep test is realized.(2)Taking the Tangjiatun tunnel as the engineering background,under the condition of satisfying the normal stress,the method of drilling is used to artificially create the damage space,so that the soil will be damaged during the secondary consolidation creep process,and the long-term strength of the soil is determined.the long-term strength of the soil is determined.(3)The soil secondary consolidation creep loading and unloading test was completed,and the relationship between strain and water content and pressure was analyzed based on the data obtained from the test.(4)According to the strain time curve obtained by the experiment,based on the unified rheological mechanics model theory,combined with the strain curve for model identification,the model which can characterize the sub-consolidation creep of soil is obtained,and the model is verified by nonlinear fitting.Choose the correctness and rationality.The secondary consolidation creep process does not cause damage due to the lateral limitation of the ring cutter.Therefore,this paper creates artificial space for the soil destruction and combines the obtained strain time curve to determine the long-term strength of the Q3 loess in the Tangjiatun tunnel.The subconsolidation creep curve obtained by the experiment identifies the corresponding constitutive model,which has certain theoretical and engineering guiding significance for the support design of the tunnel under secondary consolidation creep and the study of soil stability.