反拱水垫塘底板块轴力在上举力作用下的变化规律探讨

Discussing Regularities for Change of Axial Forces Between Slabs of Inverted Arch Plunge Cushion Pool by Uplift Force

为研究反拱水垫塘底板块轴力特征,以溪洛渡高拱坝和反拱水垫塘为参照,在高水头、大流量作用下,以反拱水垫塘在止水破坏、拱圈单底板块、五底板块和九底板块锚固分别失效为代表工况,对拱圈底板块的轴力在上举力作用下的变化规律进行了试验研究。研究表明,拱圈底板块轴力产生和传递的机理是,底板块上举力诱导了底板块位移和锁定,锁定后相邻底板块产生了约束轴力,同时轴力又反过来向相邻底板块传递直至拱端。轴力沿程可分为冲击强振区和上下游强振区。在冲击强振区,底板块瞬时值较大,时均值小,脉动强度最大,拱圈底板能瞬时锁定形成瞬时拱;在上下游强振区,底板块瞬时值和时均值大,而脉动强度较小,拱圈底板块能长时间锁定形成局部拱。在3个强振区,底板块轴力的优势频率在小于0.2 Hz的低频窄带。试验条件下拱圈底板块不发生强度破坏、共振破坏。反拱水垫塘运用时,应控制底板块位移、减少拱圈锁定底板块数,才能使轴力分布在合理范围。

By taking Xiluodu high arch dam with high water head and large discharge rate as reference,an experimental research on axial forces regularities for change of a single and nine slabs on arch ring was conducted to study characteristics of axial force by considered of anchoring on them being all out of function by uplift force.The study results showed that the mechanism of axial forces generation and transmission was that the slabs shift and locked were induced by uplift forces,then the adjacent slabs could affect constraint axial forces,conversely the axial forces would transfer to the adjacent slabs eventually to arch abutments.Axial forces distribution could be divided into impacting intensity vibration region,upriver and downriver intensity vibration region.In impacting intensity vibration region,time-average of axial force was small,instantaneous maximum was big,and fluctuation intensity was big,therefore slabs could be locked in short time and instantaneous arch formed.But in upriver and downriver intensity vibration region,time-average was big,instantaneous maximum was big,and fluctuation intensity was small,therefore slabs could be locked for a long time and local arch formed.The dominant frequency of slabs was in the low-frequency narrow range of lower 0.2 Hz in these three intensity vibration regions.When inverted-arch plunge pool is in operation,radial displacement should be controlled,the number of locked slabs be reduced,and magnitude of axial forces be in rational range.