Solution mining of potassium chloride

Claim 1

IN THE METHOD OF RECOVERING POTASSIUM CHLORIDE FROM A WATER-SOLUBLE SUBTERRANEAN STRATUM CONTAINING POTASSIUM CHLORIDE AND SODIUM CHLORIDE BY ESTABLISHING A CAVITY IN THE STRATUM AND FEEDING WATER TO THE CAVITY TO DISSOLVE POTASSIUM CHLORIDE FROM THE STRATUM THEREBY FORMING A POTASSIUM CHLORIDE-RICH SOLUTION WHICH IS WITHDRAWN FROM THE CAVITY, THE IMPROVEMENT WHICH COMPRISES INCREASING THE RATE OF RECOVERY OF POTASSIUM CHLORIDE FROM THE CAVITY BY ALTERNATELY REDUCING THE WATER PRESSURE IN THE CAVITY SUFFICIENTLY TO CAUSE COLLAPSE OF THE CAVITY ROOF AND INCREASING THE WATER PRESSURE WITHIN THE CAVITY TO PREVENT FURTHER COLLAPSE OF THE CAVITY FOOR UNTIL THERE IS OBTAINED A SUBSTANTIALLY INCREASED CONCENTRATION OF POTASSIUM CHLORIDE IN THE BRINE REMOVED FROM THE CAVITY, AND THEN FEEDING WATER INTO THE CAVITY AT INCREASED PRESSURE TO EXTRACT POTASSIUM CHLORIDE TO OBTAIN A SUBSTANTIALLY INCREASED CONCENTRATION OF POTASSIUM CHLORIDE IN THE BRINE REMOVED FROM THE CAVITY.