1.0.1 This code is formulated with view to ensuring the safety and normal use normal use of building (including structure) in collapsible loess region and realizing technical advancement, economic rationality and environmental protection.
1.0.2 This code is applicable to the survey, design, foundation treatment, construction, use and maintenance of construction engineering in collapsible loess region.
1.0.3 As for the construction in collapsible loess region, comprehensive measures based on foundation treatment according to the collapsible loess characteristics, engineering requirements and local conditions shall be taken to prevent the harm of foundation collapse to building.
1.0.4 The construction engineering in collapsible loess region shall not only meet the requirements of this code, but also meet those specified in the relevant national mandatory standard.
2 Terms and Symbols
2.1 Terms
2.1.1 Collapsible loess
Loess of which the soil structure is rapidly damaged and visibly collapsed where immersed by water under pressure.
2.1.2 Noncollapsible loess
Loess having no visibly additional collapse where immersed by water under pressure.
2.1.3 Loess collapsible under overburden pressure
Collapsible loess having visibly additional collapse where immersed by water under the deadweight of overburden.
2.1.4 Loess noncollapsible under overburden pressure
Collapsible loess having no visibly additional collapse where immersed by water under the deadweight of overburden.
2.1.5 Recently deposited loess
The Holocene ( ) loess with short deposition time, low bearing capacity, poor uniformity and has larger deformation under 50~150Kpa pressure.
2.1.6 Compression deformation
Settlement generated by loess or other soil with natural moisture and structure under pressure.
2.1.7 Collapse deformation
The additional settlement generated by the collapsible loess or other collapsible soil (like undercompacted plain fill plain fill and miscellaneous fill) where immersed by water after settlement and stabilization under pressure.
2.1.8 Initial collapse pressure
Pressure where the collapsible loess collapses after water saturation.
2.1.9 Coefficient of collapsibility
Additional settlement generated by the sample of cutting ring with unit thickness certain pressure and under water saturation after settlement stability.
2.1.10 Coefficient of collapsibility under overburden pressure
Additional settlement generated by the sample of cutting ring with unit thickness under saturated deadweight pressure of overburden after settlement stability.
2.1.11 Measured collapse under overburden pressure
Deadweight collapse generated by all collapsible loess layer saturated by water immersion through test pit immersion test in collapsible loess site.
2.1.12 Computed collapse under overburden pressure
Accumulative value of deadweight collapse calculated by indoor compression test according to the coefficient of collapsibility under overburden pressure of collapsible loess sample and the site conditions.
2.1.13 Computed collapse
Accumulative value of collapse calculated by indoor compression test according to the coefficient of collapsibility under overburden pressure of collapsible loess sample and the site conditions.
2.1.14 Remnant collapse
Collapse obtained by subducting the collapse of the proposed treatment soil layer from the Computed collapse of collapsible loess foundation.
2.1.15 Protection distance
Minimum distance to prevent building foundation from effect of leakage from pipeline and water pool.
2.1.16 Area of protection
Area within the protection distance around the building.
2.2 Symbols
A - the foundation area
a - the coefficient of compressibility
b - the width of foundation bottom
d - the embedded depth of foundation or the diameter of pile shaft (or pile hole)
Es - the compression modulus
e - the void ratio
fa - the characteristic value of corrected foundation bearing capacity
fak - the characteristic value of foundation bearing capacity
Ip - the plasticity index
l - the length of foundation bottom or pile shaft
pk - the corresponding to the average pressure on the foundation bottom under standard load effect combination
P0 - the average additional pressure on foundation bottom
Foreword I 1 General Requirements 2 Terms and Symbols 2.1 Terms 2.2 Symbols 3 Basic Requirements 4 Survey 4.1 General Requirements 4.2 Site Survey 4.3 Test to Determine Loess Collapsibility (I) Indoor Compression Test (II) Site Static Load Test (III) Site Test Pit Immersion Test 4.4 Loess Collapsibility Evaluation 5 Design 5.1 General Requirements 5.2 Site Selection and General Layout Design 5.3 Building Design 5.4 Structure Design 5.5 Design for Water Supply and Drainage, Heat Supply and Ventilation 5.6 Foundation Calculation 5.7 Pile Foundation 6 Foundation Treatment 6.1 General Rules 6.2 Cushion Layer Method 6.3 Dynamic Consolidation 6.4 Compaction Method 6.5 Pre-immersion Method 7 Foundation Reinforcement and Inclination Rectification of Existing Buildings 7.1 Reinforcement by Silicification Grouting and Soda Solution Grouting 7.2 Pit-jacked Pile Underpinning 7.3 Rectification Method 8 Construction 8.1 General Requirements 8.2 Site Protection 8.3 Construction of Foundation Pit or Foundation Trench 8.4 Building Construction 8.5 Construction of Piping and Water Pool 9 Use and Maintenance 9.1 General Requirements 9.2 Maintenance and Repair 9.3 Settlement and Groundwater Level Observation Appendix A Engineering Geological Division of Collapsible Loess in China Appendix B Division of Loess Layer Appendix C Requirements for Judgment of Recently Deposited Loess Appendix D Operating Points for Taking Undisturbed Sample in Drill Hole Appendix E Examples for Various Buildings Appendix F Design Measures for Water Pool Structures Appendix G Design Measures for Building During Groundwater Level Rise of Collapsible Loess Site Appendix H Key Points of Static Load Immersion Test for Vertical Bearing Capacity of Single Pile Appendix J Key Points for Static Load Test of Cushion Layer, Dynamic Compaction and Compaction Foundations Explanation of Wording in This Code
1 General Requirements
1.0.1 This code is formulated with view to ensuring the safety and normal use normal use of building (including structure) in collapsible loess region and realizing technical advancement, economic rationality and environmental protection.
1.0.2 This code is applicable to the survey, design, foundation treatment, construction, use and maintenance of construction engineering in collapsible loess region.
1.0.3 As for the construction in collapsible loess region, comprehensive measures based on foundation treatment according to the collapsible loess characteristics, engineering requirements and local conditions shall be taken to prevent the harm of foundation collapse to building.
1.0.4 The construction engineering in collapsible loess region shall not only meet the requirements of this code, but also meet those specified in the relevant national mandatory standard.
2 Terms and Symbols
2.1 Terms
2.1.1 Collapsible loess
Loess of which the soil structure is rapidly damaged and visibly collapsed where immersed by water under pressure.
2.1.2 Noncollapsible loess
Loess having no visibly additional collapse where immersed by water under pressure.
2.1.3 Loess collapsible under overburden pressure
Collapsible loess having visibly additional collapse where immersed by water under the deadweight of overburden.
2.1.4 Loess noncollapsible under overburden pressure
Collapsible loess having no visibly additional collapse where immersed by water under the deadweight of overburden.
2.1.5 Recently deposited loess
The Holocene ( ) loess with short deposition time, low bearing capacity, poor uniformity and has larger deformation under 50~150Kpa pressure.
2.1.6 Compression deformation
Settlement generated by loess or other soil with natural moisture and structure under pressure.
2.1.7 Collapse deformation
The additional settlement generated by the collapsible loess or other collapsible soil (like undercompacted plain fill plain fill and miscellaneous fill) where immersed by water after settlement and stabilization under pressure.
2.1.8 Initial collapse pressure
Pressure where the collapsible loess collapses after water saturation.
2.1.9 Coefficient of collapsibility
Additional settlement generated by the sample of cutting ring with unit thickness certain pressure and under water saturation after settlement stability.
2.1.10 Coefficient of collapsibility under overburden pressure
Additional settlement generated by the sample of cutting ring with unit thickness under saturated deadweight pressure of overburden after settlement stability.
2.1.11 Measured collapse under overburden pressure
Deadweight collapse generated by all collapsible loess layer saturated by water immersion through test pit immersion test in collapsible loess site.
2.1.12 Computed collapse under overburden pressure
Accumulative value of deadweight collapse calculated by indoor compression test according to the coefficient of collapsibility under overburden pressure of collapsible loess sample and the site conditions.
2.1.13 Computed collapse
Accumulative value of collapse calculated by indoor compression test according to the coefficient of collapsibility under overburden pressure of collapsible loess sample and the site conditions.
2.1.14 Remnant collapse
Collapse obtained by subducting the collapse of the proposed treatment soil layer from the Computed collapse of collapsible loess foundation.
2.1.15 Protection distance
Minimum distance to prevent building foundation from effect of leakage from pipeline and water pool.
2.1.16 Area of protection
Area within the protection distance around the building.
2.2 Symbols
A - the foundation area
a - the coefficient of compressibility
b - the width of foundation bottom
d - the embedded depth of foundation or the diameter of pile shaft (or pile hole)
Es - the compression modulus
e - the void ratio
fa - the characteristic value of corrected foundation bearing capacity
fak - the characteristic value of foundation bearing capacity
Ip - the plasticity index
l - the length of foundation bottom or pile shaft
pk - the corresponding to the average pressure on the foundation bottom under standard load effect combination
P0 - the average additional pressure on foundation bottom
Contents of GB 50025-2004
Foreword I
1 General Requirements
2 Terms and Symbols
2.1 Terms
2.2 Symbols
3 Basic Requirements
4 Survey
4.1 General Requirements
4.2 Site Survey
4.3 Test to Determine Loess Collapsibility
(I) Indoor Compression Test
(II) Site Static Load Test
(III) Site Test Pit Immersion Test
4.4 Loess Collapsibility Evaluation
5 Design
5.1 General Requirements
5.2 Site Selection and General Layout Design
5.3 Building Design
5.4 Structure Design
5.5 Design for Water Supply and Drainage, Heat Supply and Ventilation
5.6 Foundation Calculation
5.7 Pile Foundation
6 Foundation Treatment
6.1 General Rules
6.2 Cushion Layer Method
6.3 Dynamic Consolidation
6.4 Compaction Method
6.5 Pre-immersion Method
7 Foundation Reinforcement and Inclination Rectification of Existing Buildings
7.1 Reinforcement by Silicification Grouting and Soda Solution Grouting
7.2 Pit-jacked Pile Underpinning
7.3 Rectification Method
8 Construction
8.1 General Requirements
8.2 Site Protection
8.3 Construction of Foundation Pit or Foundation Trench
8.4 Building Construction
8.5 Construction of Piping and Water Pool
9 Use and Maintenance
9.1 General Requirements
9.2 Maintenance and Repair
9.3 Settlement and Groundwater Level Observation
Appendix A Engineering Geological Division of Collapsible Loess in China
Appendix B Division of Loess Layer
Appendix C Requirements for Judgment of Recently Deposited Loess
Appendix D Operating Points for Taking Undisturbed Sample in Drill Hole
Appendix E Examples for Various Buildings
Appendix F Design Measures for Water Pool Structures
Appendix G Design Measures for Building During Groundwater Level Rise of Collapsible Loess Site
Appendix H Key Points of Static Load Immersion Test for Vertical Bearing Capacity of Single Pile
Appendix J Key Points for Static Load Test of Cushion Layer, Dynamic Compaction and Compaction Foundations
Explanation of Wording in This Code
