Foundation Pit Support Research Articles

Research on the Stress and Deformation Characteristics of Circular Foundation Pit during Excavation in Sand Soil

The stress and deformation response characteristics of the support structure in the process of excavation and support of circular sand foundation pit are complex. The existing research results lack a general analysis method for the mutual check between the field monitoring data and the numerical simulation results. This research relies on the excavation and support project of a circular foundation pit in the sandy soil layer of the west anchorage of Humen Second Bridge. The force and deformation characteristics of foundation pit soil are monitored and structure is supported during construction. A new method for checking simulation parameters based on the excursion monitoring data of the diaphragm wall is proposed. The modeling and calculation theory of foundation pit excavation and support process is established. The superposition calculation of pore water pressure is used to realize the foundation pit seepage-stress coupling. The effects of steady-state seepage conditions on the equivalent strain of foundation pit soil, the displacement of the diaphragm wall, and the axial force of the lining are compared and analyzed. The stress and deformation mechanism of the soil layer and supporting structure during the excavation and support of a circular foundation pit in the sand layer is obtained.

Construction Design of Prestressed Cast in place Piles for Transmission Line Engineering in Plateau Areas

With the growth of urban construction, the excavation depth of foundation pit construction is getting deeper and deeper. Adding soil anchor to cast-in-place pile is one of the most effective methods for deep foundation pit support. And the construction quality of cast-in-place pile and soil anchor directly affects the subsequent construction and the safety of buildings. As an important pile type, pile foundation often has some quality problems such as pile position deviation, excessive sediment, concrete segregation, mud inclusion, broken pile and so on. Therefore, in the construction, it is necessary to correctly select the construction technology, strengthen the quality control of the construction process, ensure the integrity of the pile body, and make the static pressure test reach an excellent state. In the construction of electric power engineering, the links between the steps are very close, so only strict quality management of each process can really ensure the quality of transmission line construction. Combined with the engineering practice, this paper analyzes the quality problems of bored piles in plateau area and puts forward the prevention measures, providing suggestions for the construction design of prestressed bored piles in transmission line engineering.

Application of High-pressure Jet Grouting Pile in Deep Foundation Pit Excavation and Support Scheme around the Original Natural Foundation

Application of High-pressure Jet Grouting Pile in Deep Foundation Pit Excavation and Support Scheme around the Original Natural Foundation

Research on internal force of 3-D modeling of fish belly beam supported in foundation pit based on computer intelligent stress monitoring system

High prestressing force stiffness fish belly beam tool type combined internal support system, referred to as IPS construction method, is a new type of internal support structure system for deep foundation pit support, which is developed based on the principle of prestress and aiming at the shortcomings of traditional concrete internal support and steel support through a large number of engineering research and practical application, it is composed of fish belly beam (high-strength and low relaxation steel strand as the upper chord member. H-shaped steel as the stress beam, and H-shaped steel support beam with different length, butt brace, corner brace, column, cross beam, pull rod, triangular joint, preloading and jacking device and other standard components, and prestress is applied to form a plane restressed support system and three-dimensional structure system. Compared with the traditional concrete internal support and steel support, it greatly improves the overall stiffness and stability of the support system. Combined with the remote real-time monitoring system, it can effectively and accurately control the displacement of the foundation pit and greatly reduce the deformation of the foundation pit. This technology has made a major breakthrough in the internal support technology of deep foundation pit support. It is the most advanced internal support technology in the world. In this paper, a 3-D model of fish belly beam foundation pit support system is established completely, the stress characteristics of the support system are analysed by computer intelligent stress monitoring system, and the distribution areas of prestress and internal support stress are summarized, which can be used as a reference for this type of engineering experience in the future.

Influence of Thermal Behavior on the Safety Performance of the Pit Enclosure near Railway Foundations under Solar Radiation

Thermal behavior often affects the performance of thin-walled steel structures and even becomes one of the controlling loads. Steel pipes are often used in foundation pit support. This problem of the thermal stress of steel pipes is very important. The Huhang Railway, a section of the high-speed railway from Huzhou to Hangzhou in Zhejiang Province, China, was examined in this study. In this paper, the displacement and stress in pit 358# of the Huhang Railway near the railway foundation was monitored, and a thermal coupling model was established. The temperature field distribution inside the foundation pit was calculated through solar radiation and ambient temperature, and the displacement and stress of the supporting structure and enclosure structure were calculated using the thermal expansion coefficient. The following conclusions were drawn from the comparison: (1) In addition to solar radiation, ambient radiation should also be taken into account at the same time, especially in the calculation of the substructure. (2) The temperature of the support structure was unevenly distributed, and the maximum temperature difference between the steel pipes on the east and west sides could reach from 18.9 °C up to 58.8 °C. The height angle of solar radiation was the main factor that led to this situation. (3) The difference in stress between the support structure and the enclosure structure was positively related to the change in temperature. When the temperature rose, the stress increased, and the horizontal displacement of the enclosure structure decreased, which was beneficial to the stability of the foundation pit and vice versa. (4) The thermal behavior had different effects on the stress at different depths and times, and had spatial and temporal heterogeneity. The enclosure stresses had a certain delay in response to temperature changes. The reasons for this are yet to be investigated.

Numerical Simulation of Anchorage Force and Deformation of Pile in Deep Mixed Soil Foundation Pit

Foundation pit support plays a pivotal role in the process of urbanization in our country. The emergence of new support forms has dramatically enriched the diversity of foundation pit support. The pile-anchor support structure is a new type of support structure that has emerged with the development of foundation pit engineering in recent years. However, the current theoretical research on the foundation pit pile-anchor support system often cannot meet the improvement of the on-site construction technology level, and many calculation models based on assumptions cannot truly reflect the relationship between the foundation pit support structure and the soil layer, and the piles The stress and deformation characteristics of the anchor support system itself[1]. With the rapid economic development and the continuous expansion of the urban construction scale, the foundation pit problem caused by high-rise buildings and underground traffic has become a hot issue in civil engineering. Foundation pit accidents often occur due to design errors. 3D numerical simulation can better simulate the whole process of foundation pit excavation and support, and provide displacement and internal force prediction data for actual construction, thereby effectively preventing foundation pit accidents. Midas finite element software performs numerical simulation analysis of deep foundation pit support. Through further analysis of vertical deformation and horizontal displacement, the deformation value of the supporting structure is extracted and compared with the measured deformation value to guide the deformation control design and engineering monitor.

Design and Field Monitoring of a Pile–Anchor–Brace Supporting System in a Soft Soil Area

With the continuous development of urbanization and the rapid development of science and technology, the requirements for foundation pit engineering are getting higher and higher. Foundation pit engineering is gradually developing in the direction of larger area and deeper excavation. In engineering examples, the combined supporting structure of a pile–brace and pile–anchor for foundation pits is widely used, while the engineering examples supported by a pile–anchor–brace supporting system are less frequently used. Based on a super-large deep foundation pit project in Yancheng City, Jiangsu Province, China, according to the surrounding environmental conditions, the foundation pit support scheme, and on-site construction situation, the design and on-site monitoring of the pile–anchor–brace supporting system were introduced and analyzed. The results show that: (1) the deformation of the pile–anchor–brace supporting system shows an obvious spatial effect, and the horizontal displacement of the pile and soil of the long side direction is greater than the short side direction; (2) in the initial state, the deep horizontal displacement of the soil is in the form of a ‘cantilever’, but in the later stage it changed to the form of a ‘drum belly’, and both the brace and anchor cable can limit the displacement of the soil effectively; (3) the axial force of the brace develops rapidly in the initial stage, but its development tends to be gentle after the completion of the first anchor cable construction. Through on-site monitoring, it was found that the axial force of the ring brace was larger than that of the corner brace, which was larger than the opposite brace; and (4) the development trend of the axial force for the two rows of anchor cables is quite different. The average axial force of the first row of anchor cables is greater than the second row of anchor cables, and the development trend of the first row of anchor cables is steep first and then gentle, while the change trend of the second row of anchor cables is just the opposite.

Study on Design and Deformation Law of Pile-Anchor Support System in Deep Foundation Pit

In this study, a deep foundation pit project of Nanlishi Road in the Xicheng District of Beijing was taken as the engineering background. Based on the monitoring method of that project and referring to its design scheme principle, this study applied advanced monitoring technology methods such as anchor axial force and deep horizontal displacement monitoring. The mechanism of pile–soil interaction, the stress change and deformation law of the three-pile and two-anchor support systems of deep foundation pits, and the stability of deep foundation pit support in an anhydrous sandy pebble stratum, were studied in depth. Results show: The axial force of the anchor rod had great loss in the early stage of prestressed tension locking; with the deepening of foundation pit excavation, the lateral pressure of stratum increased gradually, and the prestress of the anchor increased until the end of excavation, where it tended to be stable; the maximum horizontal displacement of the pile was smaller than the design value, and the maximum horizontal displacement was not at the top of the pile; the axial force of the prestressed anchor varied with the formation pressure and surrounding load; the tension of the lower anchor had a certain influence on the axial force of the upper anchor. Except for the east side of the foundation pit, the anchors of the first layer were all stabilized at about 140 kN, and the anchors of the second layer were stabilized at about 150 kN. The third row of anchors on the north side was stable at around 170 kN. By analyzing the variation law of stress and deformation of the supporting structure of the foundation pit, the timeliness of the data during the construction process was improved, and a reference is provided for the informatization construction of related working conditions.

Research on Application of Foundation Pit Support in Construction Engineering

Research on Application of Foundation Pit Support in Construction Engineering

Brief Discussion on the Design and Construction of Geotechnical Engineering Deep Foundation Pit Support

Brief Discussion on the Design and Construction of Geotechnical Engineering Deep Foundation Pit Support

Application and Exploration of Deep Foundation Pit Support Construction Technology in Civil Construction

Application and Exploration of Deep Foundation Pit Support Construction Technology in Civil Construction

Research and Application of Optimization Design of Deep Foundation Pit Support

Research and Application of Optimization Design of Deep Foundation Pit Support

Application Strategy of Deep Foundation Pit Support Construction Technology in Construction Engineering

Application Strategy of Deep Foundation Pit Support Construction Technology in Construction Engineering

Discussion on Construction Technology Control of Deep Foundation Pit Support in Construction Engineering

Discussion on Construction Technology Control of Deep Foundation Pit Support in Construction Engineering

Measures to Ensure the Effectiveness of Deep Foundation Pit Support in Construction Engineering

Measures to Ensure the Effectiveness of Deep Foundation Pit Support in Construction Engineering

Application Analysis of Deep Foundation Pit Support Technology in Building Construction

Application Analysis of Deep Foundation Pit Support Technology in Building Construction

Deformation Stability Response of Adjacent Subway Tunnels considering Excavation and Support of Foundation Pit

Abstract Since the safety and stability of the original tunnel structure are easily affected by the adjacent foundation pit excavation, it is strongly necessary to study the deformation evolution of tunnels during the adjacent foundation pit excavation. With regard to the two cases that tunnel is adjacently located at the right and bottom of foundation pit, the influence of different supporting methods, including pile support, bolt support, pile-bolt support, and shotcrete-bolt support, on the tunnel stability was investigated on the basis of the whole excavation process numerical simulation of deep foundation pit for determining the best foundation pit supporting beneficial to the stability of adjacent tunnel. The results indicate that both one-step excavation and multistep excavation have great influences on the displacement of adjacent tunnels, wherein the influences on the tunnel located at the right of foundation pit are greater than those at the bottom of foundation pit. Multistep excavation is recommended for the foundation pit adjacent to shallow tunnel. In the case of the tunnel located on the bottom of the foundation pit, the maximum stress generated around the tunnel is small, the maximum stress area is limited, and the displacement of tunnel monitoring points is also small. For the tunnel located at the right of the foundation pit, the pile-bolt supporting can effectively limit the displacement of soil between the tunnel and the foundation pit, reduce the maximum stress and the maximum stress distribution area, and effectively control the tunnel displacement.

Discussion on Construction Technology of Deep Foundation Pit Support in ConstructionEngineering——An Example of Geotechnical Engineering Design in Beijing's Western Region

Discussion on Construction Technology of Deep Foundation Pit Support in ConstructionEngineering——An Example of Geotechnical Engineering Design in Beijing's Western Region

Field Test and Data Simulation of Foundation Pit Support System Based on BP Neural Network

In view of the neural network problem, a field test and data simulation study of the root pit support system is proposed. First, in some difficult cases, the BP algorithm is usually due to the low level of training, thus changing the tuition and fees. Second, the BP algorithm can mix heavy objects with special effects, but the gradient process will generate local minima, so the minimum error cannot be guaranteed. The experimental response and simulation data of the BP neural network foundation pit support system is analyzed, and all experimental data are recorded. Finally, from an empirical point of view, the results brought by the field test of the central support system are determined and ultimately, promote the development of human life. The genetics-based estimation algorithm reproduces the neural network, the estimation time is 10 s, the prediction error root floats between −0.05–0.05 mm, the maximum correlation near error is 0.36%, and the approximate IA value is higher than 0.9.

Discussion on the Application of Deep Foundation Pit Support Construction Technology in Construction Engineering

Discussion on the Application of Deep Foundation Pit Support Construction Technology in Construction Engineering