Infinite floor with object as terrain.

Hello unity community! I have a terrain made in blender.I want to Instantiate it to create an infinity world. But i cant just instantiate it on Start(). So i thought when the player collides on the terrain, run a function to Instantiate 3 more on player position.x + Collision terrain length.x . It Works perfectly. But it instantiates 3 in a row and only on x+ . There are huge problems. I just want to instantiate the terrains that i need to make an infinity world effect. Any help, ideas will be appreciated... Thanks alot.

My code is as bad as my english :P

 #pragma strict
 var terrain : GameObject;
 
 function Update () {
 
 }
 
 function OnCollisionEnter(col : Collision){
     if(col.gameObject.name == "Player"){
          
         for(var i2 = 0;i2 < 1;i2++){
         Instantiate(terrain,new Vector3(this.transform.position.x + 271,0,0),Quaternion.Euler(-90,0,0));
         Instantiate(terrain,new Vector3(this.transform.position.x + 271,0,this.transform.position.z + 271),Quaternion.Euler(-90,0,0));
         Instantiate(terrain,new Vector3(this.transform.position.x + 271,0,this.transform.position.z - 271),Quaternion.Euler(-90,0,0));
            
         }
            
       }
         
 }