考虑渗流影响的水平定向钻泥浆压力控制研究

Study on mud pressure control of horizontal directional drilling considering seepage effect

为研究在水平定向钻施工中如何合理控制泥浆压力以维持孔周土体的稳定、避免孔壁失稳,基于柱孔扩张理论,同时考虑浆液渗流和强度准则的影响,推导了孔壁周围土体的应力场、位移场和泥浆压力极限值的理论解答,并将理论值与实测值进行了对比分析.通过算例,对极限泥浆压力的控制以及渗流、强度准则等因素的影响进行了研究.结果表明:渗流对泥浆压力控制影响显著,随着渗透压力增大,泥浆压力极限值减小,孔壁处应力减小、位移增大;不同准则下的泥浆压力极限值差异较大,应根据工程实际情况选择合适的强度准则,避免高估或低估极限泥浆压力;可通过增加膨润土含量和地面注浆等措施来控制泥浆压力的影响.

In order to study how to reasonably control the mud pressure in the construction of horizontal directional drilling to maintain the stability of the soil around the hole and avoid the instability of the hole wall,based on the theory of column hole expansion,while considering the influence of seepage and strength criterion,the theoretical solutions of the stress field,displacement field and mud pressure limit value of the soil around the hole wall were derived,and the theoretical values were compared with the measured values.Through an example,the control of ultimate mud pressure and the influence of seepage and strength criterion were studied.The results show that the seepage has significant influence on the control of mud pressure.With the increase of seepage pressure,the limit mud pressure decreases,the stress at the drillhole wall decreases and the displacement increases.The limit values of mud pressure under different criteria are quite different.The appropriate strength criterion should be selected according to the actual situation of the project to avoid overestimating or underestimating the limit mud pressure.The influence of the mud pressure can be controlled by increasing the content of bentonite and ground grouting.