My server has falled down

My server has falled down

My server has falled down since I have tried to install apc. I just have
installed php-pear and apache2-prefork-mem. Now my server does not respond
and don't know why.
[Tue Aug 20 11:07:01.123491 2013] [core:notice] [pid 16080] AH00094:
Command line: '/usr/sbin/apache2'
[Tue Aug 20 11:14:33.510798 2013] [mpm_prefork:notice] [pid 16080]
AH00169: caught SIGTERM, shutting down
[Tue Aug 20 11:14:34.698790 2013] [mpm_prefork:notice] [pid 17880]
AH00163: Apache/2.4.6 (Ubuntu) PHP/5.5.1-2+debphp.org~precise+2 configured
-- resuming normal operations
[Tue Aug 20 11:14:34.698977 2013] [core:notice] [pid 17880] AH00094:
Command line: '/usr/sbin/apache2'
Any idea of how to solve it? I've tried to remove them but nothing changes