Method for mining or moving of sand or gravel from underwater deposits

摘要

Disclosed is a method for mining sand or gravel from a sand or gravel deposit at the bottom of a body of water, comprising the following steps: i) providing mining machinery capable of conveying sand or gravel from a mining position at the bottom of the water to a desired location, the mining position being at a level relatively lower than the upper limit of the deposit of sand or gravel to be mined; ii) providing water injection means capable of injecting water into the sand or gravel deposit iii) injecting water into the deposit by the injection means such that the injection is performed substantially directly into the surface of the deposit to be treated by injection, wherein the injection means is held in contact with the surface of the sand or gravel and is neither inserted into the layer nor held at a distance above the surface of the deposit, in an amount and at a rate selected so that the sand or gravel and the injected water form a liquefied layer, the liquefied layer being capable of flowing under the influence of gravity from the place of the deposit to the lower level mining position, and iv) mining the sand or gravel by means of the mining machinery, after the sand or gravel has flowed from the deposit to the mining position. A similar method for removing sand or gravel is also disclosed, comprising the following steps: i) providing water injection means capable of injecting water into the sand or gravel deposit, ii) injecting water into the deposit by the injection means such that the injection is performed substantially directly into the surface of the deposit to be treated by injection, wherein the injection means is held in contact with the surface of the sand or gravel and is neither inserted into the layer nor held at a distance above the surface of the deposit, in an amount and at a rate selected so that the sand or gravel and the injected water form a liquefied layer, the liquefied layer being capable of flowing under the influence of gravity from the place of the deposit to a desired position lying at a level relatively lower than the upper limit of the deposit, and iii) permitting the sand or gravel to settle from that liquefied layer at the desired position.