SQL & PL/SQL :: Import With A Default Constraint On Table?

I have a table as below. This table is not partitioned.

create table t1
(
d1 date,
n1 number not null
);

[Code]....

I took an export dump of the above table and after that I renamed the table t1 to t1_old. Then I recreated the table as below with a default constraint on d1 field.

create table t1
(
d1 date default to_date('01/01/1100','DD/MM/YYYY','NLS_CALENDAR=GREGORIAN'),
n1 number not null

[Code]....

But the problem here is the data import is taking too much time than what I expected. I can't afford a maxvalue partition here as of my DBA team mentioned if you add maxvalue partition adding partition later in a stage is difficult on this table

apply in this scenario and make the import faster. I am using oracle 10.2.0.1.0 version.