I have managed to fix it at my own.
I have used following code to update post meta
update_post_meta($post_id, 'tb_data', base64_encode(serialize($new_value_array)));
…and following code to get post meta
$tb_meta = get_post_meta($post->ID, 'tb_data', true);
$tb_meta_unserialized = unserialize(base64_decode($tb_meta));
I hope this will help someone.