An apparatus for drilling hole, comprising: a cluster drill of down-the-hole percussion hammers, the cluster drill of DTH percussion hammers comprising two or more DTH percussion hammers each equipped with a drill bit and said drill bits being arranged in two or more circumferential layers covering a circular drilling area or an annulus drilling area; a special distributor for distributing compressed air or pressurized fluid from two or more supply sources to the cluster drill of DTH percussion hammers, the special distributor being connected to the cluster drill of DTH percussion hammers; and a rotary head for providing rotational turning speed and output torque for the apparatus, the rotary head being connected to the special distributor; wherein the DTH percussion hammers are supplied with the compressed air or pressurized fluid from two or more independent supply sources, and each of DTH percussion hammers is supplied with the compressed air or pressurized fluid from one of the independent supply sources; and wherein within each of the circumferential layers, at least one of the DTH percussion hammers is supplied with the compressed air or pressurized fluid from one of the independent supply sources that is different from the independent supply source supplying the other DTH percussion hammers such that when one or more drill bits at one circumferential layer is causing direct exhaustion of the compressed air or pressurized fluid from one of the independent supply sources due to impacting on soft ground of a mixed ground formation comprising both hard and soft ground during drilling, at least one other drill bit in the same or different circumferential layer supplied with the compressed air or pressured fluid from the other independent supply source continues to hammer and penetrate the mixed ground formation in the absence of direct exhaust phenomenon and wherein the special distributor having one or more rotatable intake swivels (110, 111) for sourcing the compressed air or pressurized fluid from one or more of the independent supply sources, and each of the rotatable swivels is sourcing one of the independent supply sources. a cluster drill of down-the-hole percussion hammers, the cluster drill of DTH percussion hammers comprising two or more DTH percussion hammers each equipped with a drill bit and said drill bits being arranged in two or more circumferential layers covering a circular drilling area or an annulus drilling area; a special distributor for distributing compressed air or pressurized fluid from two or more supply sources to the cluster drill of DTH percussion hammers, the special distributor being connected to the cluster drill of DTH percussion hammers; and a rotary head for providing rotational turning speed and output torque for the apparatus, the rotary head being connected to the special distributor; wherein the DTH percussion hammers are supplied with the compressed air or pressurized fluid from two or more independent supply sources, and each of DTH percussion hammers is supplied with the compressed air or pressurized fluid from one of the independent supply sources; and wherein within each of the circumferential layers, at least one of the DTH percussion hammers is supplied with the compressed air or pressurized fluid from one of the independent supply sources that is different from the independent supply source supplying the other DTH percussion hammers such that when one or more drill bits at one circumferential layer is causing direct exhaustion of the compressed air or pressurized fluid from one of the independent supply sources due to impacting on soft ground of a mixed ground formation comprising both hard and soft ground during drilling, at least one other drill bit in the same or different circumferential layer supplied with the compressed air or pressured fluid from the other independent supply source continues to hammer and penetrate the mixed ground formation in the absence of direct exhaust phenomenon and wherein the special distributor having one or more rotatable intake swivels (110, 111) for sourcing the compressed air or pressurized fluid from one or more of the independent supply sources, and each of the rotatable swivels is sourcing one of the independent supply sources.