CALAIS, France — The migrants from Afghanistan, Sudan, Eritrea and elsewhere keep coming. Almost 100 a day arrive at this dusty, ramshackle camp perched at the edge of the English Channel, just 31 miles from Britain, their ultimate goal.

The French authorities have tried for 18 months to dismantle the vast camp, known as the Jungle. In their last attempt, in March, when about 4,000 people lived here, they leveled almost half of it. But since then, the camp has almost doubled in size. It is larger than ever, and it remains one of the most visible symbols of Europe’s inability to cope with the influx of so many desperate people.

Dazed and ragged, new migrants stumble up the industrial road from nearby Calais every day, past the graphite electrode factory and underneath the well-guarded highway overpass that serves as the entrance to the camp, where three Afghan boys recently took shelter.