This was a temporary access ramp that was used before the Chai Wan Depot was constructed. This Access Ramp is supposed to connect to an at-grade Temporary Depot's southwest around today's Lei King Wan. The access ramp leads eastwards from the existing Tai Koo Siding through a retaining wall near Po Yeung Court. After the Chai Wan Depot was built, the temporary depot was demolished and the access ramp's undergrade areas were filled in. Today, the remains are still seen on the retaining wall mounted near Po Yeung Court as two tunnels filled in with sand.
Sources:
https://www.thmalex.com/railway/chi/mtrtrip.html (only accessible through Wayback Machine)
https://www.checkerboardhill.com/2011/04/railway-abandonment-in-hong-kong/
https://hkrail.wiki/images/archive/b/b4/20240303091000%21TDx.pdf
Comments
The link
Hi there, I am able to access the link through wayback machine, I have quoted relevant parts and a photo for your reference.
"鯉景灣的廢置地鐵隧道出口
住在鯉景灣的居民，相信都未必知道鄱陽閣旁的一堵護土牆，曾是經是地鐵隧道出口。看到這裡，大家可能會問，這裡可沒有地鐵車站，為什麼路軌會伸延到這裡來？原來，在興建港島線時，因柴灣車廠仍未竣工，因此需要在西灣河的新填海區（即現時之鯉景灣）上建造一個臨時車廠，以便工程車停泊及進行維修，而在車廠的西南面（即鄱陽閣旁），設有隧道與太古站的路軌側線相連，讓工程列車進出地鐵管道。在柴灣車廠建成後，這個臨時車廠便隨即被廢置並拆卸，而該連接隧道亦在後來被泥土回填及封閉。
昔日的車廠及連接隧道位置圖
雖然該隧道的出口現在已經被封閉，但大家仍可以在那兒看見那個出口，在鄱陽閣旁的行人路，有一個雜物房，在這個雜物房的右邊，有兩個塞滿了沙泥的大洞，靠右的一個便是昔日的地鐵隧道出口了。
值得一提的是，靠左的一個洞是用作從康愉街旁的山頭輸送泥土進行填海工程之用，它與該地鐵隧道為同一結構，而在相關工程完成後它亦與地鐵隧道一樣被封閉。"
Thanks to EthanCK
I am here to deliver my sincere gratitude to you for actually using a Wayback Machine (I have no idea what that is)