基于有效摩擦因数的顶管隧道摩阻力计算方法研究

Study on calculation method of friction resistance of pipe jacking tunnel based on effective friction coefficient

为降低顶管管壁摩阻力,顶管工程施工过程中往往需要在管壁与土体之间注入泥浆,以改变管节-土体的接触状态,使其由管节-土体全接触转变为部分管土与部分管浆接触状态。从摩擦学基本理论出发,结合既有的3种土压力计算方法,对管土部分接触状态下顶管摩阻力计算问题进行研究。通过引入有效摩擦因数来表征管节-土-泥浆的接触状态,进而在Persson接触模型的基础上,提出考虑管节-土体与管节-泥浆接触角度的有效摩擦因数计算模型,构建出一种适合于管节-土体部分接触条件下的顶管摩阻力计算方法,并开展实例验证和参数影响分析。研究结果表明:与既有方法相比,本文方法充分考虑了地质特性参数(如内摩擦角、黏聚力、容重等)、设计参数(埋深、施工间隙、管径等)及泥浆减阻效果的影响,工程适用性更强。混凝土顶管直径在0.6~4 m范围,接触角度普遍在10°~60°之间,有效摩擦因数在0.01~0.1之间变化。富水条件下,宜采用太沙基计算土压力,而对于非富水情况,则德国“ATVA 161”修正土压力模型更为适用;在采用合理的土压力模型的基础上,预测结果与实测值吻合良好,证明了该方法的适用性与有效性。

In order to reduce the friction resistance of pipe jacking,slurry is usually injected between pipe jacking and soil in pipe jacking engineering.Thus,the contact state of the full contact between pipe joint and soil changes to the state of partial contact between pipe-soil and partial contact pipe-slurry.In this paper,the problem of pipe jacking friction under partial contact of pipe and soil was studied.According to the basic theory of tribology,three typical silo models were introduced and compared.The effective friction coefficient of pipe jacking was introduced lies on the interaction between the pipe,slurry and soil.To solve the problem of effective friction coefficient calculation,the model of the contact angle between the pipe and soil was established by using the PERSSON contact theory.Finally,a method for jacking friction resistance under partial contact of pipe and soil was presented.For further research,example validation and parameter analysis were carried out.The following results were obtained.Compared with existing methods,the method has a better engineering application by taking the influence of lubrication,soil properties(such as internal friction angle,cohesion,void ratio,etc.)and design parameters(such as buried depth,overcut,pipe diameter,etc.)into consideration fully.The results are drawn as follows.The contact angle is generally in the range of 10°~60°,and the equivalent friction coefficient varies between 0.01~0.1,when the diameter of concrete pipe is in the range of 0.6~4 m.The Terzaghi’s silo model is suitable for abundant water condition,while the AVT A-161(Germany)method is more used in the condition without water.By using reasonable silo models,the predicted results are in good agreement with practice.The results can prove the applicability and effectiveness of this method for various formation and design conditions.