How to concatenate a javascript object to a post form?

I have an object JSON that I built at runtime, I need it to be sent to my servlet , along with the other form fields, via post, how do I do this? I researched a lot but nothing worked.

function createJSON() {

    layoutColunas = [];
    $(".colSubWrapper").each(function() {

        var item = {};

        var nomeColuna = $(this).find(".colJSON").eq(0).val();
        item ["nome_coluna"] = nomeColuna;

        var tipoColuna = $(this).find(".colJSON").eq(1).val();
        item ["tipo_coluna"] = tipoColuna;

        layoutColunas.push(item);

    });

    return layoutColunas;
}
$("#formBaseCadastrar").on("submit", function(e){

    e.preventDefault();

    console.log("tentou fazer submit");
    var layoutColunas = createJSON();
    $('.colJSON').prop('disabled', true);
    var data = $("#formBaseCadastrar").serialize();
    data = data + '&' + $.param(layoutColunas);
    console.log(data);
    $.ajax({ 
        url: "/QualidadeWeb/basesCadastrar",
        type: "POST",
        async: false,
        data: data,
        success: function(data){
            console.log(data);
            $("#pageContainer").load("/QualidadeWeb/resultado?resp="+encodeURIComponent(data));
        },  
        error: function(data){
            console.log(data);
            console.log("deu errado");
        }
    });
});

Although my object works normally, this $.param(layoutColunas); function creates a undefined param. When using f12 for tracking the Post Protocol, the result was as follows:

nomeBase=base1234&conexao=234234&telefone=324234&tipoBase=4&undefined=&undefined=

My object is as follows:

Thank you in advance!