Wpautop stops working after get_the_excerpt

<div <?php post_class('post');?> id="post-<?php the_ID();?>">
    <div class="date" title="<?php the_time('g:i a'); ?>">
        <span class="month"><?php the_time('F'); ?></span>
        <span class="day"><?php the_time('d'); ?></span>
        <span class="year"><?php the_time('Y'); ?></span>
    </div>
    <div class="text">
        <h4><a href="<?php the_permalink();?>"><?php the_title();?></a></h4>
        <?php if($post_type=='post'):?>
        <div class="meta">
            <a href="<?php echo get_author_posts_url( get_the_author_meta( 'ID' ) ); ?>" title="<?php printf(__('Posted by %s','wi') , get_the_author() ); ?>" rel="author" class="author"><?php the_author(); ?></a>
            <span class="slash">/</span>
            <?php comments_popup_link( __('Leave a comment','wi'), __('1 comment','wi'), __('% comment','wi'), 'comment-link', __('Comments are closed','wi') ); ?>
        </div>
        <?php else: // post type == 'portfolio'?>
        <div class="categories">
            <?php echo get_the_term_list( get_the_ID(), 'category', '', '<span class="slash">/</span>', '' );?>
        </div>
        <?php endif; // endif post_type ?>
        <div class="excerpt">
            <p><?php echo substr(get_the_excerpt(),0,80);?> &hellip;</p>
            <div><a href="<?php the_permalink();?>" class="readmore"><?php _e('Read more &rarr;','wi');?></a></div>
        </div>
    </div>
    <div class="clearfix"></div>
</div>

Above is a loop I’ve used for my shortcode. The problem is: when i add the line get_the_excerpt inside the code block, wpautop stops working after that. After removing get_the_excerpt, everything is back to normal.

Anyone knows how to solve this problem?