Lien image en survol mobile tablette responsive

<div class="portfolio_item portfolio_item2">
<a href="projet_quicksilver_pro.html"><img src="assets/images/Portfolio/quicksilver_pro_france.jpg" alt="" /></a>
<div class="portfolio_hover text-center">
<h6 class="text-uppercase text-white">Identité événementielle</h6>
<p class=" text-white">Quicksliver Pro France</p>
<div class="portfolio_hover_icon">
<a href="projet_quicksilver_pro.html"><i class="fa fa-expand"></i></a>                                            
</div>
</div>
</div>

.main_portfolio{
    width:100%;
    overflow: hidden;
}
.portfolio_item{
    position: relative;
    overflow: hidden;
}
.portfolio_item:hover img{
    -webkit-transform: scale(1.1);
    -moz-transform: scale(1.1);
    -o-transform: scale(1.1);
    -ms-transform: scale(1.1);
    transform: scale(1.1);
}
.portfolio_item img{
    width:100%;
    -webkit-transition: all 0.6s;
    -o-transition: all 0.6s;
    -moz-transition: all 0.6s;
    -ms-transition: all 0.6s;
    transition: all 0.6s;
}
.portfolio_hover{
    position: absolute;
    left:0%;
    right:0%;
    top:0%;
    width:100%;
    height: 100%;
    background-color:rgba(0, 0, 0, 0.30); 
    padding-top: 12%;
    opacity: 0;
    -webkit-transition: all 0.4s;
    -moz-transition: all 0.4s;
    -o-transition: all 0.4s;
    -ms-transition: all 0.4s;
    transition: all 0.4s;
}
.portfolio_item:hover .portfolio_hover{
    opacity: 1;
}
.portfolio_item2 .portfolio_hover{ 
    padding-top: 25%;
}
.portfolio_item3 .portfolio_hover{ 
    padding-top: 65%;
}