gs can be used to service the retreat face on both sides of intervening pillars, due to account should be taken of the depth of cover to plan adequate pillars. It is important to prevent the first retreat face from influencing the stability of the crosscut [37] junctions [38]. Such junctions should be kept in minimum to avoid support problems at face-ends when the second face retreats. This can be major problems at depths greater than 300m.E. A retreat system with multiple entries [39]: this system is the typical layout for longwall mining in the U.S.A. This system separates entry development from coalface operation and represents an integration of both pillar and longwall mining concepts. The development entries usually consist of triple roadways and continuous mines with room-and-pillar mining technology are used to develop the entries. The longwall is mined in retreat with a shearer type of machine and the roadway towards the gob area is allowed to collapse with the gob.
The ventilation system can become complex due to the existence of many entries and the need to provide positive ventilation [40] to individual working.
The least width of the chain pillars [41] has to be determined to protect the roadways of the retreating face against excessive closure effects from the abutment pressure zone. This method also requires good roof condition to avoid roof control problems at crosscut intersections during longwall retreating.
NOTES TO THE TEXT
[1] longwall mining system������ʽ���ɲ�úϵͳ
[2] inclined coal seams����бú��
[3] longwall advance mining�� ����ǰ��ʽ����
[4] longwall retreat mining�����ں���ʽ����
[5] strata pressure���Ҳ�ѹ��
[6]roadway��ƽ��
[7] panel������
[8] capital outlay�������������
[9] geological conditions����������
[10] single entry������
[11] abutment pressure��֧��ѹ��
[12] shearer������Ͳʽ����ú��
[13] gob���ɿ���
[14] arches set������֧��
[15] pack�������ԣ������
[16] Pump Pack����վ
[17] roadway maintenance��ƽ��ά��
[18] double entries��˫��
[19] rib pillars��������ú��
[20] deformation������
[21] gob closure ���ɿ������װ��ƽ�
[22] offset������������
[23] block-out�����ֳ�
[24] high stress����Ӧ��
[25] stability���ȶ���
[26] reinforcement����ǿ���ӹ�
[27] down-dip���������
[28] strike������
[29] integrated advance and retreat system��ǰ�������ʽ���ϵIJ�úϵͳ
[30] face-end���������ͷ
[31] ��Z�� system����Z���β�úϵͳ
[32] maingate����������ƽ���˳��
[33] tailgate�����λط�ƽ���˳��
[34] bleeder roadway��ͨ��ƽ�����ˮƽú�㷿��ʽ���ɣ�
[35] methane emissions�������
[36] headings��ƽ����ͷ
[37] crosscut��ʯ�ţ����������
[38] junctions�� ��������
[39] multiple entries������
[40] positive ventilation����ѹ��ѹ��ʽ��ͨ��
[41] chain pillars���������ʽ��ú��
��һҳ[1][2][3]
