multi-query loop

multi-query.php

<?php
$tabs = 4;
for( $i = 0; $i < $tabs; $i++ ) {

	// Use ppp for the offset, we're going to multiply this by the tabs
	$posts_per_page = get_option( 'posts_per_page', 10 );

	/**
	 * Multiplies posts per page, by the current tab index we're on.
	 *
	 * WARNING: this breaks pagination - https://codex.wordpress.org/Class_Reference/WP_Query#Pagination_Parameters
	 * Though since you're using this in tabs, I'm sure pagination isn't an issue.
	 */
	$offset = $posts_per_page * $i;

	$my_query = new WP_Query( array(
		'category_name'  => 'my_category',

		// Offset allows you to 'pad' the posts by a number, so if the number were 10, it will skip the first 10 posts.
		'offset'         => $offset,
		'posts_per_page' => $posts_per_page,
	) );

	// Note the use of shorthand if/while statements, you can certainly use brackets instead.
	if ( $my_query->have_posts() ) : 
		while( $my_query->have_posts() ) : $my_query->the_post();

		/**
		 * Notes:
		 * 
		 * 1.) You do not have to 'echo get_the_post_thumbnail', I used the_post_thumbnail() instead, does the same thing, without having to use the post id.
		 * 2.) Do not 'echo the_title()', just use the_title() instead, it is an echoing statement, or use get_the_title( $post_id )
		 * 
		 */
		?><li role="tab" data-toggle="tab" rel="bookmark" title="<?php the_title(); ?>"><?php the_post_thumbnail( array( 100, 100 ) ); ?> <?php the_title(); ?></li><?php

		endwhile; 
	endif;

}