Heaving or squeezing would be indicated by which of the following signs?

The answer

Heaving or squeezing is indicated by a bulge at the bottom of the excavation, frequently with water seeping upward through the trench floor.

Heaving happens when the weight of the surrounding soil (a surcharge load) presses down on the ground next to and beneath an excavation and forces the soil at the bottom to push up and inward into the open cut. Squeezing is the closely related sideways version — soft or saturated soil is squeezed into the trench from the walls. Both are signs that the excavation is losing its stability and can precede a collapse.

So on an OSHA trenching question, the correct sign to select is the one describing upward movement, bulging, or heaving of the trench bottom — not cracks at the surface or dry, crumbling walls, which point to different failure modes.

Why the other signs point elsewhere

Excavations fail in several distinct ways, and the exam distractors usually describe those other modes:

• Tension cracks running parallel to the top edge signal an impending sliding or sloughing failure of the wall, not heaving from the bottom.
• Spalling or crumbling / raveling of the face (small chunks flaking off the wall) indicates drying, vibration, or loss of cohesion — again a wall-face problem, not bottom heave.
• Toppling, where a slab of the wall rotates and falls into the trench, is driven by tension cracks and undercutting.
• Boiling is the specific condition where water flowing upward through the bottom bubbles up sand — it is a groundwater/quick-condition sign. It often accompanies heaving but is technically the upward water movement; the defining sign of heaving/squeezing is the soil bulge itself.

Heaving is set apart by the direction of movement: the trench floor rises or bulges because soil is being displaced into the cut.

The bigger picture

OSHA's excavation standard (29 CFR 1926 Subpart P) requires a competent person — someone trained to identify hazards and authorized to correct them — to inspect the excavation daily, before each shift, and after any event (rain, vibration, added loads) that could change conditions. Recognizing heaving is part of that role.

What causes and prevents it:

• Causes: high surcharge loads (spoil piles, equipment, or adjacent structures placed too close to the edge), soft or saturated clay, and high groundwater or seepage pressure beneath the cut.
• Prevention: keep spoil piles and equipment back at least 2 feet from the edge, control and dewater groundwater, and use a protective system — sloping, benching, shoring, or a trench box (shield) — sized for the soil type. Deeper excavations and wetter or granular soils need more aggressive protection.

Remember the trigger depth: a protective system is generally required for excavations 5 feet deep or greater (and always when a competent person sees signs of instability like heaving, regardless of depth).