Effect of Pressure Relief Hole Spacing on Energy Dissipation in Coal Seam at Various Mining Depths

The large diameter pressure relief borehole is one of the most effective technical means to prevent and control rockburst during deep mining. Based on the engineering background of rockburst mines, the mechanical model of coal energy dissipation of large diameter pressure relief holes is established by theoretical analysis, and the approximate formula for calculating energy dissipation of coal is obtained. Combined with numerical simulation methods, the energy accumulation and dissipation laws of coal under various mining depths and the various spacings of pressure relief holes is studied. The results show that the upper and lower ends of the pressure relief holes have the highest degree of energy dissipation and the largest range of energy dissipation. While the energy dissipation effect on the left and right sides of the pressure relief holes is poor, a high accumulation of elastic strain energy occurs at a certain distance on the left and right sides of the relief holes. The dissipated energy of the coal seam increases continuously with the increase in mining depth and the decrease in spacing of pressure relief holes. The dissipated energy rises especially suddenly when the hole spacing changes from 1.0 m to 0.5 m. For coal seams with high rockburst risk, the spacing of pressure relief holes can be set to be less than or equal to 0.5 m, which can greatly improve the energy dissipation effect of coal seams. The studies can provide a theoretical basis for the optimization parameters of pressure relief holes for rockburst prevention

Surgical resection of pulmonary metastases from colorectal cancer: 11 years of experiences.

To analyze the benefits and prognostic factors after surgical resection of pulmonary metastases from colorectal cancer (CRC).From Jan. 2004 to Jan. 2015, continuous 88 cases diagnosed with pulmonary metastases from CRC, including 15 cases of synchronous metastases and 73 metachronous metastases, were analyzed in the retrospective study.All of these 88 cases underwent curative pulmonary resection including 8 cases of simultaneous surgery. The one-year, three-year and five-year survival of the 88 cases were 93.4%, 60.2% and 35.7%, respectively. 63 patients just have one metastasis, and 25 patients have more than one metastasis. Additionally, the one-year, three-year and five-year survival was 98.1%, 70.2% and 40.3% respectively in one metastasis group, while 80.1%, 37.9% and 22.5% respectively in more than one metastasis group (p = 0.003). DFS of 37 metachronous metastases were equal or greater than 18 months, and DFS of 36 metachronous metastases were less than 18 months. The one-year, three-year and five-year survival was 97.8%, 77.9% and 41.4% respectively in the DFS≥18 month group, while 88.2%, 44.6% and 28.1% respectively in the DFS<18 month group (p = 0.01).Surgical resection of pulmonary metastases from colorectal cancer can improve survival rate in selected patients. It seems that the number of metastases is an independence prognostic factor in surgical treatment. Furthermore, longer DFI implies longer survival for resectable CRC pulmonary metastases

Clinical data.

<p>Clinical data.</p

Difference between the thoracotomy group and the VATS group.

<p>Difference between the thoracotomy group and the VATS group.</p

Postoperative recurrence.

<p>Postoperative recurrence.</p

There was no statistical significance (p = 0.676) between synchronous metastasis patients metachronous metastasis patients.

<p>There was no statistical significance (p = 0.676) between synchronous metastasis patients metachronous metastasis patients.</p

Longer DFS means longer survival in metachronous pulmonary metastases patients (p = 0.011).

<p>Longer DFS means longer survival in metachronous pulmonary metastases patients (p = 0.011).</p

Though it seemed the CEA<5ng/ml group had a better behavior in survival than CEAastases.

<p>Mected patients. I"5 months, and 36 months or moreated.</p

Treatment data.

<p>Treatment data.</p