基于DTM阈值分割法的孔裂隙煤岩体瓦斯渗流数值模拟

 在岩溶发育地区开展大型工程多采用钻孔灌注桩基础，而桩底溶洞的存在可能造成塌孔、埋钻、漏浆等事故，给在建工程和周围建筑造成重大影响。由于钻孔灌注桩需要泥浆护壁，现行的物探方法很难在钻孔灌注桩的泥浆内对桩底溶洞进行有效勘查。本研究结合声呐应力波传播特点，提出了一种钻孔灌注桩桩底溶洞声呐探测方法，并研发了桩底溶洞声呐探测仪(JL-SONAR)和信号分析软件(PBCA)。JL-SONAR探测仪实现了现场声呐信号的发射与采集，PBCA软件完成了探测数据的分析与整理。该技术充分利用了钻孔灌注桩的泥浆条件，可以在成孔过程中跟踪探测桩底10 m内溶洞发育情况，具有成本低、速度快、精度高等优点。并通过两个具体工程案例验证了声呐探测技术在实际工程中的应用。本文的研究对岩溶地区尤其是液态环境下的溶洞勘查提出了一种新的解决方法。

Numerical simulation of gas flow in pores and fissures of coal based on segmentation of DTM threshold

In order to obtain the real physical model to characterize the pores and fissures of coal mass and to numerically investigate the internal gas flow，the segmentation of DTM threshold was implemented to segment the CT images. The method of DTM threshold was amended by adding Wiener filter denoising. Its correctness was validated with the three-dimensional reconstruction. The abscissa value corresponding to the maximum value of the minimum on the porosity curve was found to be the optimal threshold. Numerical simulation of gas flow was conducted based on the real physical model of pores and fissures of coal extracted using the DTM threshold segmentation method. Simulation results showed that at the micro-scale(＜100 µm)，the gas flowing pores and fissures agreed with the high speed nonlinear percolation of Forchheimer. The flow velocity grew rapidly in fissures and changed randomly along the direction of flow. The permeability coefficient and non-Darcy coefficient were calculated according to the fitting parameters on average flow velocity.