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Explosive compaction technology for loess embankment settlement control: numerical simulation and field implementation

  • Haichao Li
  • Junliang TaoEmail author
  • Lianyu Wei
  • Yanzhu Liu
Research Paper
  • 66 Downloads

Abstract

Loess covers about one-tenth of the world’s land area. While it is often used as embankment fill, loess is not an ideal construction material due to its wet collapsible nature, as it may cause significant embankment settlement and other related problems. Although explosive compaction (EC) technology has been used for many years, the challenges in experimental testing and theoretical analysis hinder its wider application. This paper contributes to the development of a design construction scheme of EC technology for loess embankment improvement through an integrated approach that involves finite element modeling, small-scale experiments, full-scale simulation and field implementation. In this study, a reliable finite element model is developed and validated through a small-scale experiment. The model is developed based on the software ANSYS/LS-DYNA®14.5 and takes into account the coupling between different materials (including soil, explosives, air and pavement). Critical performance factors such as the volume of the explosion cavity, the density of the compacted soil and the soil pressure can be obtained directly from the model. The model is then extended to simulate full-scale embankments. A sensitivity study is conducted to establish the correlations between the design parameters and the abovementioned performance factors. The relationships served as design guidelines for the successful implementation of the EC technique in an embankment section on the Cheng-Chao highway in China. The results demonstrated the feasibility of the EC technique as a ground improvement method for loess embankments, and it illustrated the effectiveness of the numerical method as a tool in design.

Keywords

Embankment Explosive compaction (EC) Loess Numerical simulation Strengthening 

List of symbols

a, k

Constants of soil

\(a_{0}\), \(a_{1}\), \(a_{2}\)

User-defined constants in yield function of soil

c

Cohesive strength

dc

The length of its minor axis of the approximate spheroid

dv

The length of its major axis of the approximate spheroid

e

Void ratio

h

Diameter of the blasting-influenced zone

rc

Radius of exploration cavity

re

Equivalent radius of explosive bar

rhc

Lateral radius of compacted zone by EC

sij

Deviatoric stress of soil element

w

Water content

\(A\),\(B\)

Linear coefficients in the JWL equation

\(C_{0}\), \(C_{1}\), \(C_{2}\), \(C_{3}\), \(C_{4}\), \(C_{5}\) and \(C_{6}\)

User-defined constants in the linear polynomial equation of state

Dh

Depth of drill hole

Dha

Actual hole depth measured before blasting

Dhd

Design depth of drill hole

Dr

Relative density of soil

\(E\)

Internal detonation energy per unit volume for explosive, internal energy per initial volume for air, Young’s modulus for pavement structure

E0

Initial modulus for explosive, initial internal energy per volume for air

Er

Relative error

\(E_{\tau }\)

Tangent modulus

G

Shear modulus

Gs

Specific gravity of soil

He

Height of explosive bar

Hbc

Bottom depth of compacted zone by EC

Hbcone

Height of the bottom cone of explosion cavity

Hcy

Height of the middle cylinder of explosion cavity

Hebc

Bottom depth of effectively compacted zone by EC

Hs,Hs1,Hs2

Height of safety zone between pavement and compacted topmost point

Htc

Top height of compacted zone by EC

Htcone

Height of the top cone of explosion cavity

Ip

Plasticity index

K

Bulk modulus

\(p_{\text{air}}\)

Pressure on air element

\(p_{\text{eos}}\)

Pressure of detonation products

Psoil

Pressure on soil element

Q

Equivalence weight of explosive

R

Radius of soil in model

\(R_{1}\), \(R_{2}\), \(\omega\)

Nonlinear coefficients in the JWL equation

Sr

Saturation

V0

Initial relative volume for air

Va

Actual volume of explosion cavity

Vc

Volume of exploration cavity

\(V_{\text{rel}}\)

Relative volume, ratio of detonation products volume to undetonated high explosive volume for explosive, ratio of the changed volume to the initial one for air

WL

Liquid limit

WP

Plastic limit

W

Weight of explosive bar

W1

Preliminarily designed explosive weight

W2

Adjusted explosive weight

\(\beta\)

Hardening parameter of pavement structure

\(\gamma\)

Ratio of specific heats in the linear polynomial equation of state

\(\mu\)

Variable in the linear polynomial equation of state, Poisson’s ratio of pavement structure

\(\rho\)

Density, natural density for soil

\(\rho {}_{\text{d}}\)

Dry density of soil

\(\sigma_{\text{y}}\)

Yield strength of pavement structure

\(\varphi\)

Internal friction angle of soil

\(\phi_{\text{s}}\)

Yield function of soil

Notes

Acknowledgements

The research team would like to acknowledge the support and assistance from the Chengde Municipal Bureau of Transportation. The writing of the paper is supported by the China Scholarship Council.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Academy of TransportationTianjinChina
  2. 2.School of Civil and Transportation EngineeringHebei University of TechnologyTianjinChina
  3. 3.School of Sustainable Engineering and Built EnvironmentArizona State UniversityTempeUSA
  4. 4.Road Maintenance and Management Center of TianjinTianjinChina

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