Question
Three years ago I had a patio installed made of paving stone. Now several rows of pavers are sinking. Regular sand, not polymeric sand, was used and rain/snow have pushed out the sand. How can this be fixed since concrete was used on the cap stones and I can't easily get to the sunken paving stones?

Answer
My condolences, as it is a common problem with no easy solution.  Here is a link regarding fixing morter-less pavers:
http://www.paversearch.com/repair-pavers-guide.htm

The problem is that the base was not compacted sufficiently.  You may not have to remove the "cap stones" in order to effect a repair.  

If this is not the case, my fellow AllExperts.com ,Sean J Murphy, answered a similar question a while back regarding pavers that are mortared in place:

揟he best thing to do would be to re-grout the joints with new mortar. You'll have to first be sure to remove about 1/2inch minimum of the existing mortar to achieve a space suitable to hold the new mortar.

揟he 慡tuff?they spread was most likely mortar or Portland cement that may have been mixed with some sand (which is essentially mortar.  Other than mortar or sand you could also use 'permatill'. It is a fine gravel like substance which is actually expanded shale. It won't splash like sand and is too big generally, to stick to your shoes. Google 憄ermatill?to learn more.

揘o there is not an easy way to repair the sunken pavers, this is a common problem often due to lack of proper base preparation.  To repair the sunken pavers you need to remove them first, and chizzle away the mortar by hand.  Then re-set them as you like and re-grout the joints. However, before re-setting them you need to make sure their is a good sub-base to set them on which is level and will not fail. Consider adding a 3-4" deep sub-base of compacted granite dust/gravel or 3" min slab of concrete to lay the pavers on. Unless cars will drive on it this will be all you need.

揧ou must ensure the sub-base cannot 慺lare out?under pressure and sink or spread into the surrounding soil. If your soil is very dry and sandy you may need an edge restraint for your sub-base. Concrete would be the best option to stop sinking?br>
Sorry, not much to add to his advise.  ~Marc