Jurors at alleged Chelsea bomber Ahmad Khan Rahimi’s trial on Thursday gazed at the twisted green hulk of a garbage dumpster catapulted across West 23rd Street by a pressure cooker bomb last year and heard a police expert describe the lethal “frag blanket” he found in a second bomb.

“There’s an actual blanket of all ball bearings and lead balls and stuff which is basically just to cause pure devastation,” said NYPD bomb squad cop Jason Hallik, who disabled a device left on West 27th Street. “There’s no other purpose. . . . Picture it like thousands of guns going off at the same time.”

Hallik was the leadoff government witness on the fourth day of trial in Manhattan federal court, where Rahimi, 29, of Elizabeth, New Jersey, is charged with planting one bomb on West 23rd Street that injured 30 when it exploded at 8:30 p.m. on Sept. 17, 2016, and leaving a similar bomb on West 27th Street.

Rahimi is separately charged in New Jersey with planting bombs there and engaging in a police shootout. Prosecutors say he wanted to bring jihad to the streets of America. On Thursday, prosecutors played a video of Rahimi practicing with explosives in his backyard two days before the bombing.

Hallik, an Iraq veteran who defused improvised explosive devices there, testified that the seat of the Chelsea blast was on the north side of West 23rd Street, near a series of dark green construction dumpsters. The remains of one dumpster were found more than 100-feet away, on the south side of the street.

Over objections from Rahimi’s defense team, who said it was all for show, prosecutor Shawn Crowley dramatically peeled off a white quilt hiding the bin in a corner of the courtroom and wheeled the 100-pound hunk of metal on a wood dolly to the front of the jury box.

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It had a hole in what appeared to be the back, with bent edges and wheels inverted to the inside and a huge bulge in the front. Warning labels still visible said “Not Responsible for Injury” and “Do Not Play in or Around,” and white lettering on the side said “BIC” with a number.

“On the one side you can see where it’s pushed in from a high explosive blast and pushed out to the other end, which indicates that the explosive device had to be placed next to the dumpster,” Hallik said.

Hallik also explained how he manipulated a remote robot arm from a monitor in a command vehicle to first tug on the cellphone detonator attached to the West 27th Street bomb until the wires snapped. Hallick said he then grabbed the pressure cooker and put it in a safe “containment vessel” for transport.

It took more than an hour and a half to disable the device, Hallick said.

“You don’t want to rush it in my job,” he told jurors. “It’s very methodical.”

At the NYPD range on Rodman’s Neck in the Bronx, Hallik said, he worked on the bomb from behind a shield while wearing a bomb-resistant suit. He said he X-rayed the pressure cooker and then unsuccessfully attempted to open the tight silicon sealant, first with the robot arm and then with a winch.

It finally took a high-pressure water cannon to remove the top, Hallick said, spilling out explosive powder, nuts, ball bearings, the frag blanket and Christmas lights that were part of the trigger.

“It’s like taking bullets out of a gun,” Hallik said.