Drainage and pressure-limiting method

Method: Install collection/drainage wells and pumping wells, blind drains, discharge trenches, water-pressure release layers, etc., to lower the water level;

Applicable conditions: Projects with self-drainage conditions or where permanent dewatering and drainage facilities are permitted and equipped with an automatic control dewatering/drainage system; may be used in combination with the water-barrier pressure-control method; requires long-term operation control and maintenance management.

Water-release pressure-reduction method

Method: Install a pressure control system to reduce water pressure;

Applicable conditions: Projects where the base slab of the underground structure is embedded in low-permeability foundation soil and where a permeable and water-conducting system can be installed beneath it to collect pressurized water into a collection system; may be used in combination with the drainage pressure-limiting method and the water-barrier pressure-control method; requires long-term operation control and maintenance management.

Water-barrier pressure-control method

Method: Install a barrier system to control the buoyancy effect of the water-head difference on the foundation base slab;

Applicable conditions: Projects in low-permeability strata or where the water-head difference is not large and it is easy to install a water-barrier curtain or a retaining structure with a water-barrier function; may be used in combination with the drainage pressure-limiting method; requires long-term operation control and maintenance management.

Counterweight anti-floating method

Method: Increase the load on the foundation base slab and structure; increase the fill load on the top or cantilevered structures; install heavy counterweights such as heavy concrete and fill materials;

Applicable conditions: Projects where the anti-floating force and the buoyancy differ only slightly; may affect the design space and functionality.

Structural anti-floating method

Method: Increase the stiffness and uplift capacity of the base slab or structure; use the foundation pit retaining structure to increase vertical resistance; connect structures with large loads to form an integral anti-floating structure;

Applicable conditions: Where the anti-floating force distribution is small, the base slab stiffness of the underground structure is uneven, the anti-floating stability is insufficient, and the effective range is limited.

Anchoring anti-floating method

Method: Anti-floating anchors, anti-floating piles;

Applicable conditions:The structural forces are reasonable, the building function is not affected, and latermaintenance is simple.

"Anchor basic test"

Citing various standards and specifications

I. "Technical Code for Engineering of Ground Anchors and Shotcrete Support" GB50086-2015

12.1.10 The anchor shall be judged as failed when one of the following occurs in the anchor basic test:

1. The displacement increment of the anchor or unit anchor exceeds 2.0 mm within the specified load-holding time;

2. The anchor rod body fails.

II. "Technical Specification for Anti-floating Anchors" YB/T4659-2018

7.2.4 The anchor may be judged as failed and loading terminated when one of the following occurs:

1. The anchor tendon breaks or is pulled out of the anchor body;

2. The load cannot be maintained stable or the anchor head displacement does not converge within 6 h;

3. The plastic displacement increment produced by the subsequent load level reaches or exceeds 5 times that of the previous level;

4. The cumulative total displacement of the anchor head of a non-prestressed anchor exceeds 60 mm.

III. "Technical Specification for High-pressure Jet-grouted Expanded-base Anchors" JGJ/T282-2012

6.2.4 The anchor may be judged as failed when one of the following occurs in the anchor basic test:

1. The anchor head displacement increment produced by the subsequent load level reaches or exceeds 2 times the displacement increment produced by the previous load level;

2. The anchor head displacement continues to increase;

3. The anchor rod body fails.

IV. "Technical Standard for Anti-floating of Building Engineering" JGJ476-2019

Non-prestressed anchor E.2.7 The anchor may be judged as failed when one of the following occurs in the test:

1. The anchor head displacement increment produced by the subsequent load level reaches or exceeds 2 times the displacement increment produced by the previous load level;

2. The anchor head displacement continues to increase;

3. The anchor rod body fails, the rod body is pulled out of the anchor body, or the anchor body is pulled out.

Prestressed anchor E.2.13 The anchor may be judged as failed when one of the following occurs in the test:

1. The anchor rod body fails, the rod body is pulled out of the anchor body, or the anchor body is pulled out;

2. The plastic displacement increment produced by the subsequent load level reaches or exceeds 5 times the displacement produced by the previous load level;

3. The load cannot be maintained stable or the anchor head displacement does not converge within 6 h.

V. "Technical Specification for Retaining and Protection of Building Foundation Excavations" JGJ120-2021

A.2.6 Loading shall be terminated when one of the following occurs in the anchor test:

1. Starting from the second loading level, the anchor head displacement increment per unit load produced by the subsequent load level is greater than 5 times the anchor displacement increment per unit load produced by the previous load level;

2. The anchor head displacement does not converge;

3. The anchor rod body fails.

VI. "Technical Specification for Testing and Monitoring of Anchors" JGJ/T401-2017

5.2.10 Loading shall be terminated when one of the following occurs:

1. The anchor rod body fails;

2. In the multi-cycle loading and unloading method, the anchor head displacement increment per unit load produced by the current cycle load reaches or exceeds 5 times the displacement increment per unit load produced by the previous cycle load;

3. In the single-cycle loading and unloading method and the staged sustained loading method, the anchor head displacement increment per unit load produced by the current load level reaches or exceeds 5 times the displacement increment per unit load produced by the previous cycle load;

4. For soil anchors within 3 h and rock anchors within 2 h, the anchor head displacement does not reach the relative stability criterion of Articles 5 and 2.6 of this specification;

5. Loading has reached the estimated maximum test load or the additional (1-2) load level test has been completed, and the anchor head displacement reaches the relative displacement stability criterion.

In summary, regarding the failure criteria for anchor basic tests, apart from "anchor rod body failure," on which all codes agree, the other provisions "each have their own ideas." Based on the above, personal recommendations are as follows: