What does the unusual term "Kivras Eretz" mean?
Rashi #1 (citing Menachem ben S'ruk) and Rashbam: It means still a long distance away. 1
Rashi #2 (citing the Midrash): It refers to the time of year - in the spring, when the land is full of holes (like a sieve - Kevarah), and it is pleasant to travel (Sifsei Chachamim).
Ramban (citing the Redak): The distance that one travels between daybreak and breakfast. 2
Targum Yonasan (in Vayechi): On the way (to Efrat). 5
Which explains why Yakov buried her there in the middle of the way and did not take her to Efrat, as the Pasuk goes on to explain (Rashbam).
According to the Ramban however, it is less than a Mil from Efrat (as he discovered when he arrived in Yerushalayim), in which case it means 'approximately a (specific, known) short distance'. See also Rashi in Bereishis (48:7) citing R. Moshe ha'Darshan. Refer to 35:19:1:1**.
Rashi (Bereishis 48:7), assesses the distance as approximately two thousand Amos, the equivalent of T'chum Shabbos. The Torah uses the unusual word 'Kivras', to hint that the reason he did not bury her in the city was due to rain (refer to 35:16:1:2).
It is unclear however, how Targum Yonasan translates it here (EC. See commentaries.)
How do we reconcile this Pasuk with the Pasuk in Yirmiyah (31:14) "A voice is heard in Ramah - Rachel is crying for her children?
Ramban and Targum Yonasan 1 : The Pasuk in Yirmiyah is a Mashal, as if to say (not that Rachel was buried in Ramah, but) that - so loud were Rachel's cries for her children that they could be heard in Ramah (in the portion of her son Binyamin). 2
רש"י: בזמן...שהניר מצוי: למה זמן זה נקרא "כברת ארץ"?
גור אריה: על ידי הניר נעשית הארץ חלולה ומנוקבת ככברה.
למה מבין כל השבטים רק בנימין נולד בארץ ישראל?
מהר"ל (אור חדש, אסתר ג,ד. עמ' קכט ד"ה ויהי): על שאר ארצות ממונים השרים העליונים ורק ארץ ישראל היא חלק ה', ולכן בנימין היה מסולק מעבודה זרה ולא השתחוה לעשיו.