Neighbour removes 15 ft sand adjacent to my land making it dangerous

Sir/Madam, I have a small ancestral property. The plot adjacent to mine has been cut into smaller sites and sold. However since sand is like gold in this area, I learnt that he excavated close to 15 ft depth of his full plot taking advantage of the sloping road and apparently sold it. This has presented my property at a danger with mud sliding off every rains. There is a sudden drop at the edge of my plot and the width is small. He was to build a solid retaining wall which he did not and he is not listening to our plea. We cant build a house since the structure would have issues of future stability. Pls. advise my options, understand excavating soil and selling is illegal. The new owners of the sites are helpless. Thanks