Okay, you need this:
<?php echo do_shortcode('[your-first-shortcode]'.'[your-second-shortcode]'); ?>
Just write a dot between your shortcodes…
Try:
<?php echo do_shortcode( '[vc_row][vc_column width="1/1"][vc_accordion][vc_accordion_tab title="Section 1"][vc_column_text]'.'[table]'.$sometabledata.'[/table]'.'[/vc_column_text][/vc_accordion_tab][vc_accordion_tab title="Section 2"][/vc_accordion_tab][/vc_accordion][/vc_column][/vc_row]' ); ?>