锚索预应力蠕变损失计算新模型及工程应用

Research and application of a new coupled model of anchor prestress loss and rock creep

锚索预应力蠕变损失持续时间长、作用机理复杂、影响因素多样,给锚固工程长期预应力的维持带来极大的挑战;为了推进锚索预应力蠕变损失变化规律的研究,基于等效应变原理,并考虑其自身松弛特性,将预应力锚索及被锚固围岩分别由松弛模型、广义开尔文体模型模拟,提出了一种可描述预应力损失与围岩蠕变之间相互作用关系的新元件耦合模型,并推导了其本构方程、蠕变方程、松弛方程,从理论上解释了预应力损失与围岩蠕变之间的计算关系;以济南市山东高速广场配套高层深基坑工程桩锚支护体系为依托,通过理论计算、现场测试、公式拟合等方法,深入分析了锚索长期预应力变化规律,验证了计算模型的适用性、可靠性;研究表明：该计算模型可较好地反映围岩蠕变对预应力损失的变化趋势,但不能体现预应力损失总体变化水平;围岩蠕变引起预应力水平变化大致历经三个阶段,即初期（0~10d）迅速减小,中期（10~20d）趋于平稳变化,后期（20~60d）保持基本不变;围岩蠕变对预应力总损失的贡献率仅为50%,是预应力设计水平的15%,因此,其他因素引起的损失同样不可忽略;研究成果为锚固工程的设计、施工及长期预应力的预测提供了理论依据和技术支持。

Because of long duration,complex mechanisms,diverse factors,anchor prestress creep loss brought a great challenge to maintaining a long-term prestress level of anchor. In order to further study the creep loss variation rule of anchors prestress,based on the principle of equivalent strain while taking the inherent properties of the material itself into consideration simultaneously,the anchor and rock were respectively simulated by the relaxation model and general Kelvin,so a new creep calculated model which could better describe the relationship between prestress loss and rock creep,was proposed. And its constitutive equations,creep equation,relaxation equation were deduced,which could theoretically explain the relationship of prestress loss and rock creep deformation. Taking a deep foundation pile-anchor supporting system of Shandong Expressway Plaza in Jinan City as an example,creep loss variation laws were analyzed by theoretical calculations,field testing,formulas fitting method. Results show that： the new model can well reflect the variation law of prestress loss caused by rock creep,but does not embody the change of total prestress loss. Prestress loss caused by rock creep mainly experiences three periods of initial rapidly decrease during 0 ~ 10 d,medium stabilized changes during 10 ~30 d,late basically unchanged during 30 ~ 60 d. Contribution rate of rock creep to prestress total loss is nearly 50%,and it occupies about 15% of the designed prestress level,comparatively,the presstress of other element could usually be not ignored. It provided a theoretical basis and technical support for the design and construction of similar projects.