The phrase "accumulated substantial" is correct and usable in written English.
It can be used when describing the gathering or collection of a significant amount of something over time.
Example: "The research team has accumulated substantial evidence to support their hypothesis."
Alternatives: "gathered considerable" or "collected significant".
Although that plea would not bring a fine, the former aides have accumulated substantial legal bills.
Others were listed as employees of several school districts and accumulated substantial credits in the state's employee retirement system.
By the middle of 1988, when the fighting ended, it had accumulated substantial foreign debts, which it still has.
AT&T Canada has accumulated substantial losses and debt in a battle to break into the domestic telecommunications market.
In the process they accumulated substantial foreign-exchange reserves (while also giving a boost to domestic exporters).
LOUIS UCHITELLE During the rising stock market of the 1990's, many workers accumulated substantial amounts in their defined-contribution retirement plans, particularly 401 k)'s.
Traditionally, most people draw up wills after they are married, have children or accumulate substantial assets.
This was a period when businessmen were beginning to accumulate substantial surpluses, and overseas exploration and trade presented expanded investment opportunities.
Blunt renal artery injuries are rare and no single trauma center can accumulate substantial experience for meaningful conclusions about optimal therapeutic strategies.
The margin requirements for futures purchases are much lower than those for stock purchases, so he was able to put up a relatively modest amount of cash, while using borrowed money to accumulate substantial holdings.
While that has made for a orderly financial system for Canada that is very profitable for bank investors, the banks now find themselves accumulating substantial capital without effective ways to use it to increase their businesses within Canada.
