WASHINGTON — Sometime in the next several weeks, if all goes as planned, 159 huge blocks of granite will be loaded aboard ships in the seaport of Xiamen, China, for an 11,000-mile journey to Washington.

The cargo includes one block that bears the likeness of Martin Luther King Jr. and the dreams of generations of African-Americans.

The other blocks — which weigh as much as 55 tons each — make up the rest of the mammoth, three-part sculpture that is the centerpiece of the $120 million memorial to the civil rights leader.

More than a decade in the making, finally “it’s here,” said Ed Jackson Jr., the project’s executive architect. Assembly is scheduled to begin this year.

The memorial, the first on the Mall honoring an African-American, also will be a monumental construction project.

It will require erecting one of the biggest figurative sculptures in Washington — a three-story-tall relief of King — atop a landscape of compressed mud. (The carving of King’s head alone weighs 46 tons.)

It will require driving more than 300 concrete piles as deep as 50 feet through the dirt to support the monument’s foundation. This must be done without damaging the adjacent Tidal Basin seawall, which has already sunk into the muck at the Jefferson Memorial across the basin. A multimillion-dollar seawall repair project is under way there.

And it will require that the three parts of the sculpture have cores of concrete, rather than solid granite, to reduce weight.

Authorized by Congress in 1996, the King memorial has weathered 14 years of fundraising challenges, artistic controversy and bureaucratic squabbles.

Complaints erupted when a sculptor in China was selected to execute the chief parts of the design. More trouble came after the U.S. Commission of Fine Arts criticized the sculptor’s image of King as too grim and totalitarian. And the project was held up for months recently by a dispute over the kind of security elements the memorial should have.

But on Oct. 29, with problems resolved, Interior Secretary Ken Salazar signed the construction permit. Work on the site began in December, a project official said. Total construction time is estimated to be 20 months.

‘Stone of Hope’

Next month, a delegation from the Washington-based foundation that is building the memorial is scheduled to visit China for a final look at the sculpture before its shipment here, currently set for sometime in March or April.

“It’s going to be happening very soon,” Jackson said.

The carving is about 80 percent complete, project officials said. The sculptor, Lei Yixin, plans to finish the work in Washington as the pieces are assembled this summer and fall.

The King memorial, located not far from the Lincoln Memorial where King delivered his “I Have a Dream” speech in 1963, is to be built on a crescent-shaped, 4-acre site amid the city’s famed cherry trees.

The three main elements resemble a simulated stone mountain from which the center has been carved out and placed by itself in the foreground.

The centerpiece — named the Stone of Hope for a line from the 1963 speech — is 30 feet 8 inches tall and bears the image of King in a business suit with his arms folded.

Although not as large as some of Washington’s equestrian monuments, it will be bigger than the 19-foot statue of Jefferson in the Jefferson Memorial, the 19-foot, 6-inch statue of Abraham Lincoln in the Lincoln Memorial and the 19-foot, 6-inch statue of Freedom on the U.S. Capitol dome.

“That is a really massive piece of sculpture,” said Kirk Savage, professor of the history of art and architecture at the University of Pittsburgh and the author of a recent book on Washington’s monuments.

The two background pieces — together called the Mountain of Despair from the same line in the speech — are of similar size and frame a walkway through which visitors may pass to get to the King sculpture.

Each of the three parts weighs thousands of tons, even with a core of concrete, and will rest on the mushy ground beneath the Mall west of the Washington Monument. Hence the pilings.

Many of the Mall’s monuments, including the Lincoln Memorial, the Jefferson Memorial and the FDR Memorial, rest on pilings for support. The World War II Memorial rests on almost 500 piles, according to Kenneth Terry, construction executive with Tompkins Builders, one of the King project contractors. “If it didn’t, it would sink,” he said.

Jackson, the executive architect, said: “It’s like having cookie dough. We’re driving piles into the cookie dough. It’s like sticking your finger into it, and you stick your finger into it until you get to the bottom of the pan.”

The ground is soft because it is mostly mud that was dredged from the Potomac River in the late 1800s and used as fill.

An eye on the seawall

The adjacent Tidal Basin seawall will be carefully monitored because of the way it has sunk at the Jefferson Memorial. “There are probably potential problems around the entire Tidal Basin with the seawall,” Jackson said.

But Terry, the construction executive, said the mud is not expected to transmit severe vibrations from the pile drivers to the seawall. Pile driving could begin next month, he said.

The sculptures will be assembled from the granite blocks, much like a child might build with a set of toy blocks. Each block is cut and carved. Once they are disassembled in China, they will be shipped, probably aboard several vessels, to Baltimore, then put into storage until needed, Jackson said.

On the Tidal Basin, they will be lifted by a huge crane that will put them in place to form the facades of the sculptures. After the bottom row of blocks is placed in a kind of circular pattern, concrete will be used to fill in the center.

“You create a ring, and then you pour the center with concrete,” Jackson said. “Then you do another ring, and you pour again, until you work all the way up.”

Jackson said the three main elements are far too big to be made of solid granite: “How would you lift it?” he asked.

Savage noted that the tradition of colossal sculpture goes back to ancient times.

“We know it in the United States from the Statue of Liberty and Mount Rushmore,” he said. “But in Washington, this will be a very, very unusual piece of work. … It’s almost like a pyramid they’re building.”