A back-to-work drive appeared under way yesterday in the Appalachian coalfields, signaling the first break in the wave of wildcat strikes that have idled as many as 70,000 miners in the past six weeks.

At least 9,500 strikers - most of them from West Virginia - reported back to work since the weekend, according to the Bituminous Coal Operators Association.

A spokesman for United Mine Workers District 29 in Beckley, W. Va., said a majority of the mines in that southern West Virginia district, the union's second largest, were operating yesterday.

Meanwhile, officials of the UMW's largest district, District 17 in Charleston, W. Va., met yesterday on the union's strike problems and planned to meet again today.

Throughout the areas where miners have been striking to protest a cutback in medical benefits, UMW officials have reportedly been urging the strikers to return to work on grounds that nothing could be gained by continuing the protest.

The strikes here cut coal production, thus reducing the royalties that finance the miners' benefits - a kind of vicious circle that has caused both industry and union officials to urge the miners to return to work.

At the peak of the protest last week, more than one-third of the UMW's 180,000 working miners were on strike and the BCOA estimated that the benefit trust funds were losing $1 million a day.