沉管隧道垄沟碎石基床工程特性试验研究

Test research on engineering characteristics of crushed stone foundation with furrows for immersed tunnel

通过室内大型载荷模型试验研究沉管隧道带垄沟碎石基床的力学特性。试验碎石基床的加载方法包括满铺碎石、压拢顶、压垄沟3种,模型宽1.2 m,高0.8 m,长2.0 m。试验过程中测量竖向荷载、表面沉降和位移、垄沟空间变化、混凝土加载梁的钢筋应力发展以及试验槽侧移。结果表明:直至750 kPa的荷载压力下,3种碎石基床试验中沉降和荷载呈线性变化,说明碎石基床处于压密的弹性阶段;加载过程中,垄沟空间随荷载增加呈线性减小,并被逐渐压平;带垄沟碎石基床与满铺碎石基床的荷载沉降曲线基本一致,最终沉降基本一致,可以认为垄沟对基床力学性质无显著影响,但在工程中应计入由于垄沟存在导致接触面积差异,试验还发现带垄沟碎石基床的混凝土加载梁钢筋应力较满铺碎石基层情况下增加20%~30%;建立了带垄沟碎石基床数值模拟方法,模拟结果表明:满铺、压垄沟碎石基床的荷载沉降曲线基本一致,也证明2种基床的变形和承载力一致。

The characteristics of deformation and mechanism of furrowed crushed stone foundations for immersed tunnel are studied by plate loading tests on large-scale models with a length of 2 m,a height of 0.8 m and a width of 1.2 m which cover three conditions,i.e.loading on full-paved stone foundation,on the top between furrows,and over a furrow.Measurements include the applied load,surface displacement,furrow space and the stresses of reinforcing bars in concrete loading girder,and lateral displacement of test tank.The test results show that in all three tests,the surface settlement and the load bear a linear relationship under a load up to 750 kPa,indicating that the stone foundation is in the elastic stage of compaction;the loading curves in three tests are basically coincident and the final settlements are almost identical.It can be considered that the furrows pose no significant effect on the mechanical properties of stone foundation;during the loading process,the furrow space decreases linearly with an increase of the load,and then the furrow is gradually flattened;however,we should pay attention to the furrow effect in design that the stresses of the reinforcing bars of reinforced concrete load ding girder in furrowed stone foundation are about 20%to 30%higher than those in the full-paved stone foundation,and there will be a sharp stress increase upon a certain load;a numerical modeling method for the furrowed stone foundation is also established and the modeling results show that the load-displacement curves of the full-paved and furrowed stone foundation are basically the same,which also prove that the deformation and bearing capacity of the stone foundation are identical.