SEOUL, South Korea — Heavy downpours lashed South Korea for a ninth day on Monday as rescue workers struggled to search for survivors in landslides, buckled homes and swamped vehicles in the most destructive storm to hit the country this year. At least 40 people have died, 34 others are injured and more than 10,000 people have had to evacuate from their homes since July 9, when heavy rain started pounding the country.