C++: Map 3 elements to one key in std::unordered_multimap

My question is an extension of the following question: Searching and Inserting in a map with 3 elements in C++

In addition to the above mentioned case, I would like to have an extra pair in map as given below definition.

std::unordered_multimap<unsigned int, 
      std::pair< std::pair<unsigned int, unsigned int>, float>> wedgeAlphaMap;

This does not work well. All the time when I emplace values for the second variable in the pair(i.e. vi2), I am getting a garbage value. (code shown below)

wedgeAlphaMap.emplace(vi0, std::make_pair(std::make_pair(vi1,vi2), alpha) );

How I can properly make use of it/ or do I have missed something?