热干扰下能量桩热力特性现场试验研究

Field tests of the thermal-mechanical characteristics of energy piles during thermal interactions

能量桩的换热效率及其热致应力与变形问题,是影响其在实际工程中推广应用的重要因素之一。然而,针对在相互热干扰情况下能量桩群桩的换热效率及其热力响应特性的实测数据仍相对较少。该文依托1×3能量桩排桩基础,开展3.0 kW加热工况下热响应特性现场试验,实测中间桩和边桩的温度、应变与应力等变化规律,着重分析中间桩与边桩热力响应特性的异同点,并与能量桩单桩试验响应特性进行对比,分析1×3排桩中能量桩换热效率、热致位移、热致侧摩阻力以及中性点位置等热力响应特性变化规律。结果表明:该试验条件下,1×3能量桩排桩的换热效率约为93%;热致侧摩阻力的中性点出现在桩体约0.4倍桩长位置;中间桩和边桩最终分别产生0.5‰倍桩径(0.28 mm)和0.3‰倍桩径(0.18 mm)的桩顶位移。

The heat transfer efficiency,induced thermal stresses and energy pile deformation are key problems in energy pile designs.However,there has been little research on the heat transfer efficiencies and thermal-mechanical characteristics of energy piles caused by thermal effects.Field tests using a row of energy piles(1×3)with 3.0 kW heating were conducted to study the thermal-mechanical characteristics of the piles.The temperatures,strains and stresses of the middle and end piles were measured to study the differences with comparisons to a single energy pile with 3.0 kW heating.The results showed the heat transfer efficiencies,thermally induced displacements,thermally induced lateral friction resistances and the neutral point positions of the energy pile.The results show that the heat transfer efficiency of the 1×3 energy row piles is about 93%for these test conditions.The neutral point of the thermally induced lateral friction appears at about 0.4 times the pile length.The displacement of the top of the middle pile is 0.5‰times the pile diameter(0.28 mm)while that of the edge pile is 0.3‰times the pile diameter(0.18 mm).