The displacement of Native Americans during this period was to some extent the result of deliberate government policy, though more displacement occurred than was perhaps planned. The destruction of their way of life was (particularly once the displacement was over) definitely deliberate.
There is no question that the US government wanted the Native Americans to be moved to reservations. However, the fact that the Indians kept getting moved over and over as gold or other resources were found on their land was not planned. This was, instead, a case of the government reacting to the actions of settlers and prospectors.
Once the Native Americans were on reservations, it was clearly government policy to destroy their way of life and to "civilize" them. This can be clearly seen in such things as the creation of Indian boarding schools and the passage of the Dawes Severalty Act of 1887.