WO2021223617A1 - 模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置和试验方法 - Google Patents

模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置和试验方法 Download PDF

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WO2021223617A1
WO2021223617A1 PCT/CN2021/089801 CN2021089801W WO2021223617A1 WO 2021223617 A1 WO2021223617 A1 WO 2021223617A1 CN 2021089801 W CN2021089801 W CN 2021089801W WO 2021223617 A1 WO2021223617 A1 WO 2021223617A1
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pile
model
soft clay
filled
soil
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PCT/CN2021/089801
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English (en)
French (fr)
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周佳锦
龚晓南
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浙江大学
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Publication of WO2021223617A1 publication Critical patent/WO2021223617A1/zh

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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D33/00—Testing foundations or foundation structures

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  • the invention relates to a test device for studying the soil squeezing effect of precast pile construction and the bearing performance of the pile foundation in the field of geotechnical engineering, and particularly relates to the experiment on the study of the soil squeezing effect of the pile foundation construction and the bearing performance of the pile foundation when there are loose drainage materials around the precast pile
  • the device can be used to study the soil squeezing effect of precast pile construction when the permeability coefficient of the dispersed drainage material around the pile and the diameter of the dispersed drainage material layer are different, and the bearing characteristics of the precast pile after the pore water pressure in the soil around the pile is completely dissipated.
  • Precast piles are widely used due to their high industrial production speed, high pile strength and low cost. Used in actual projects.
  • the permeability coefficient of the soft clay layer is very small, and the excess pore water pressure dissipates slowly. It often takes several years for the excess pore water pressure to completely dissipate.
  • a layer of loose material with good drainage performance around the precast pile can be used as a drainage channel to accelerate the dissipation of the excess pore water pressure in the soft clay generated during the construction of the precast pile, thereby speeding up the recovery of the strength of the soft clay.
  • the presence of the bulk material layer can also improve the friction characteristics of the pile-soil contact surface of the precast pile.
  • the influence range of the soil squeezing effect during the process of pressing the precast pile into the soil, the dissipation process of the soil excess pore water pressure after the precast pile is pressed into the soil, and the bearing performance of the pile foundation are all the same as those of the traditional pressure.
  • the built-in precast piles are different, which needs to be studied.
  • the purpose of the present invention is mainly to study the soil squeezing effect of the pile foundation construction and the bearing performance of the pile foundation when there are scattered drainage materials around the precast pile, and to provide a method that can be used to simulate the different diameters and different permeability coefficients of the scattered drainage materials around the pile. It is a test device for the squeezing effect of precast pile construction and the bearing characteristics of the precast pile after the pore water pressure in the soil around the pile is completely dissipated.
  • a test device for simulating the bearing performance of the pile foundation of the prefabricated piles filled with scattered drainage materials including a model box, a reaction beam, a loading motor and a circular sleeve.
  • the model box is welded by steel plates.
  • the side of the box is welded with I-beam to increase the rigidity of the model box, and the bottom of the model box is welded with a steel support;
  • the reaction beam is welded to the model box;
  • the loading motor is fixed on the reaction beam;
  • Clay layer During the filling process of the soft clay layer, earth pressure sensors and pore water pressure sensors are embedded in the pile tip and the soil around the pile, which are used to measure the earth pressure and pore water pressure, respectively.
  • the soil in the soil around the pile The pressure sensor and the pore water pressure sensor are both fixed on the vertical rigid pipe; after the soft clay layer is filled and consolidated, a circular sleeve with an open end is inserted at the design model pile position; the soft clay inside the circular sleeve Take out the clay; fill in the internal space of the circular sleeve with granular drainage materials such as sand and gravel, and remove the circular sleeve from the soft clay to obtain a cylindrical space filled with the granular drainage material; insert the model The pile is pressed into the cylindrical space, so that scattered drainage materials are evenly distributed around the model pile.
  • the distance between the side wall of the model box and the circular sleeve needs to be 10 times the diameter of the circular sleeve.
  • the water content of the soft clay layer must be at least 1 times the liquid limit water content before filling, and the mixing should be uniform. After the filling of the soft clay layer is completed, it needs to wait 30-90 days for consolidation.
  • earth pressure sensors for measuring earth pressure and pore water pressure sensors for pore water pressure are provided at different depths of the pile end of the model pile.
  • a circular sleeve with an open end is inserted into the soft clay.
  • the diameter of the circular sleeve is larger than the diameter of the model pile, and the diameter of the circular sleeve is generally 1.5-3.0 times the diameter of the model pile.
  • the soft clay inside the round sleeve is taken out and filled with granular drainage materials such as sand, and then the round sleeve is taken out of the soft clay layer.
  • model piles are pressed into the granular drainage materials such as sand and gravel, and the model piles are inserted into the center of the granular drainage materials, so that the granular drainage materials such as sand and gravel are evenly distributed around the model piles.
  • the permeability coefficient of the bulk drainage material is 10 4 -10 5 times that of the soft clay layer.
  • the pile ends of the model piles are closed and the pile ends are tapered with a cone angle of 30-60 degrees.
  • the limit loading value of the loading motor is 200kN, the stroke is 100mm, and the loading motor directly loads the top of the model pile.
  • the present invention also provides a test method of the above-mentioned test device for simulating the bearing performance of the pile foundation of the prefabricated pile filled with discrete drainage materials, including the following steps:
  • the open-ended round sleeve into the design position of the model pile, then take out the soft clay inside the round sleeve and fill it with loose drainage material, and fill the inside of the round sleeve
  • the circular sleeve is taken out of the soft clay layer to obtain a cylindrical space filled with bulk drainage material; insert the model pile into the bulk drainage material so that there is a layer around the model pile Dispersed drainage material layer; when the excess pore water pressure in the soil measured by the pore water pressure sensor on the pile tip and the pile circumference is completely dissipated, the model pile is loaded by the loading motor.
  • the soil pressure sensor and pore water pressure sensor are embedded in the soil below the end of the model pile to test the soil pressure and pore water pressure in the soil at the end of the pile respectively, and the model pile can be pressed into Analyze and study the changes of soil pressure and pore water pressure in the soil at the end of the pile during the process of bulk drainage. At the same time, it can also analyze the excess pore water pressure in the soil at the end of the pile after the model pile is pressed into the bulk drainage material. Analysis and research on the law of dissipation.
  • the present invention embeds an earth pressure sensor and a pore water pressure sensor in the soil around the pile during the filling process of soft clay to test the earth pressure and pore water pressure in the soil around the pile respectively, and can press the model pile into the bulk to drain the water During the material process, the soil pressure and pore water pressure changes in the soil around the pile can be analyzed and researched. It is also possible to analyze and study the lateral soil pressure changes in the soil around the pile after the model pile is pressed into the loose drainage material. The pore water pressure change law can be studied, and the lateral earth pressure change law in the soil around the pile during the loading process can be analyzed and researched.
  • the present invention uses a loading motor to load the model piles with scattered drainage materials distributed around it, which can meet the requirements of different diameters and different permeability coefficients of the model piles around the model piles.
  • the study of soil effect the study on the dissipation of super pore water pressure of soft clay after the model pile is pressed into the granular drainage material, and the test requirements for the study of the bearing performance of the model pile when there is a layer of granular drainage material around the pile.
  • Figure 1 is a schematic diagram of a model device for inserting a circular sleeve into the soft clay after the soft clay layer is filled and consolidated;
  • Figure 2 is a schematic diagram of the model device after the soft clay inside the circular sleeve is taken out;
  • Figure 3 is a schematic diagram of the model device after the circular sleeve is filled with dispersed drainage material and the circular sleeve is taken out of the soft clay;
  • Figure 4 is a schematic diagram of the model device after pressing the model pile into the loose drainage material
  • model box 1 I-beam 1-1, steel support 1-2, soft clay layer 1-3, earth pressure sensor 1-4, pore water pressure sensor 1-5, soft clay inside the circular sleeve 1-6, bulk drainage material 1-7, model pile 1-8, vertical rigid pipe 1-9, reaction beam 2, loading motor 3, circular sleeve 4.
  • Figures 1 to 4 show the squeezing effect of the precast pile construction under the conditions of different diameters and different permeability coefficients of the dispersed drainage material around the pile of the present invention, and after the pore water pressure in the soil around the pile is completely dissipated
  • the device includes four parts: a model box 1, a reaction beam 2, a loading motor 3, and a circular sleeve 4.
  • the model box 1 is square and is welded by steel plates.
  • the side of the model box is welded with I-steel 1-1 to increase the rigidity of the model box.
  • the side length of the model box 1 is 6m, the height is 4m, and the bottom of the model box 1 is welded with steel support.
  • the reaction beam 2 is welded to the model box 1; the loading motor 3 is fixed on the reaction beam 2; the model box 1 is filled with a soft clay layer 1-3, and a soft clay layer 1- 3 Before filling, the moisture content must reach 1.5 times the liquid limit moisture content and be evenly mixed; the thickness of the soft clay layer 1-3 is 3m; the soft clay layer 1-3 is uniformly distributed in the pile end and the soil around the pile during the filling process
  • the soil pressure sensor 1-4 and the pore water pressure sensor 1-5 are buried to measure the earth pressure and pore water pressure respectively; the soil pressure sensor and the pore water pressure sensor in the soil of the pile end are buried 0.5m and 1.0m below the pile end of the model pile And 1.5m; the soil pressure sensor and pore water pressure sensor in the soil around the pile are fixed on the vertical rigid pipe 1-9, the location of the soil pressure sensor and pore water pressure sensor is 0.5m, 1.0m below the surface of the soft clay And 2.0m; the vertical rigid pipe 1-9 has a rigid pipe diameter of 10mm, and
  • the working process of the present invention is as follows: firstly, the soft clay layer 1-3 needs to be filled in the model box 1.
  • the moisture content of the soft clay layer must reach 1.5 times the liquid limit moisture content before filling and the mixing is uniform, and after the soft clay layer is filled Need to wait 30 days for the soft clay layer to consolidate; during the filling process of the soft clay layer 1-3, earth pressure sensors and pore water pressure sensors are buried in the pile tip and the soil around the pile to measure the earth pressure and pore water pressure, respectively.
  • the earth pressure sensor and pore water pressure sensor in the surrounding soil are fixed on the vertical rigid pipe; after the soft clay layer 1-3 is filled and consolidated, a circular sleeve 4 with an open end is inserted at the design position, Take out the soft clay 1-6 inside the circular sleeve, and then fill the sand and gravel and other loose drainage materials 1-7 into the inner space of the circular sleeve 4; take the circular sleeve out of the soft clay layer, and then Press the model pile into the bulk drainage material, and the center of the model pile is consistent with the center of the bulk drainage material; when the excess pore water pressure in the soft clay measured by the pore water pressure sensor embedded in the pile end and the soil around the pile is completely dissipated After that, load the model piles 1-8 through the loading motor 3.
  • the load and displacement applied by the loading motor 3 can be automatically read and stored; the model piles 1-8 are pressed into the loose drainage material 1-7 during the process of pile circumference and The earth pressure and pore water pressure in the soil at the pile tip, the pore water pressure in the soft clay after the model pile is pressed into the bulk drainage material, the earth pressure and pores in the soil around the pile and the pile tip during the loading process of the model pile.
  • the water pressure, the pile top load-displacement relation of the model pile, the pile end load-displacement relation and the pile-soil relative displacement relation can all be measured in the test.

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  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Mining & Mineral Resources (AREA)
  • Paleontology (AREA)
  • Civil Engineering (AREA)
  • General Engineering & Computer Science (AREA)
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  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
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Abstract

本发明公开了一种模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置和试验方法。所述试验装置包括模型箱、反力梁、加载电机和圆形套筒；所述模型箱由钢板焊接而成；反力梁焊接于模型箱上；加载电机固定于反力梁上；模型箱内部填筑有软黏土层；软黏土层内桩端和桩周土体内部均埋设有土压力传感器和孔隙水压力传感器；软黏土层内设有由散体排水材料填充而成的圆柱形空间，圆柱形空间用于压入模型桩。本发明结构合理，操作简单，可用于研究预制桩周围存在散体排水材料时桩周及桩端土体中超孔隙水压力变化以及桩周及桩端土体中超孔隙水压力完全消散后预制桩的承载性能，为预制桩周围填筑散体排水材料时桩基承载性能的研究提供了有效手段。

Description

模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置和试验方法 技术领域
本发明涉及岩土工程领域中预制桩施工挤土效应以及桩基承载性能研究的试验装置，特别是涉及预制桩周围存在散体排水材料时桩基施工挤土效应以及桩基承载性能研究的试验装置，可用于研究桩周散体排水材料渗透系数不同以及散体排水材料层直径不同时预制桩施工时的挤土效应以及桩周土体中孔隙水压力完全消散后预制桩的承载特性。
背景技术
随着我国城市化进程的推进，出现了越来越多的高层建筑、高速铁路、高速公路以及复杂地下基础设施，预制桩由于其工厂化生产速度快，桩身强度高且造价较低被广泛应用于实际工程中。然而我国东南沿海地区存在深厚软黏土层，土体工程性质较差，并且预制桩施工过程中会产生比较强烈的挤土效应，同时桩周软黏土中会产生较大的超孔隙水压力，由于软黏土层渗透系数很小，超孔隙水压力消散过程较慢，超孔隙水压力完全消散常常需要好几年时间，软黏土中超孔隙水压力的存在使得其强度减小，限制了预制桩极限承载力的发挥。在预制桩周围设置一层排水性能较好的散体材料层可以作为排水通道使预制桩施工过程中产生的软黏土中的超孔隙水压力消散速度加快，从而使软黏土的强度恢复速度加快，同时散体材料层的存在也可以改善预制桩的桩土接触面摩擦特性。预制桩周围存在散体排水材料层时预制桩压入土体过程中的挤土效应影响范围、预制桩压入土体后土体超孔隙水压力消散过程以及桩基的承载性能都与传统压入式预制桩不同，需要对此展开研究。
目前基本没有对预制桩周围存在散体排水材料层时预制桩压入土体过程中产生的挤土效应，散体排水材料层存在对桩周及桩端软黏土中超孔隙水压力消散过程的影响，以及散体排水材料层对桩基承载性能的影响的研究。在预制桩周围设置一层散体排水材料层能够加快软黏土超孔隙水压力消散速度以及提高桩基的承载性能，对此展开研究具有十分重要的意义。
发明内容
本发明的目的主要是对预制桩周围存在散体排水材料时桩基施工挤土效应以及桩基的承载性能展开研究，提供了一种可用于模拟桩周散体排水材料不同直径以及不同渗透系数条件下预制桩施工时的挤土效应以及桩周土体中孔隙水压力完全消散后预制桩的承载特性的试验装置。
本发明解决其技术问题所采用的技术方案是：
一种模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置，包括模型箱、反力梁、加载电机和圆形套筒，所述模型箱由钢板焊接而成，模型箱侧面焊接工字钢以增加模型箱刚度，模型箱底部焊接钢支座；所述反力梁焊接于模型箱上；所述加载电机固定于反力梁上；所述模型箱内部填筑软黏土层；所述软黏土层填筑过程中在桩端和桩周土体内部均埋设土压力传感器和孔隙水压力传感器，分别用于测量土压力和孔隙水压力，桩周土体中的土压力传感器和孔隙水压力传感器均固定在竖直刚性管上；软黏土层填筑并固结完成后在设计模型桩位置处***端部开口的圆形套筒；将圆形套筒内部的软黏土取出；将砂石等散体排水材料填筑到圆形套筒内部空间中，并将圆形套筒从软黏土中取出，得到由散体排水材料填充而成的圆柱形空间；将模型桩压入到该圆柱形空间中，使所述的模型桩周围均匀分布有散体排水材料。
上述技术方案中，进一步的，模型箱侧壁与圆形套筒之间的距离需达到圆形套筒直径的10倍。
进一步的，软黏土层填筑前含水率至少需达到1倍液限含水率并且搅拌均匀，软黏土层填筑完成后需等待30-90天进行固结。
进一步的，模型桩桩端不同深度处设有若干测量土压力的土压力传感器和孔隙水压力的孔隙水压力传感器。模型桩桩周不同深度处设有若干测量土压力的土压力传感器和孔隙水压力的孔隙水压力传感器。
进一步的，软黏土层固结完成后将端部开口的圆形套筒***软黏土中。
进一步的，圆形套筒的直径大于模型桩的直径，且圆形套筒直径一般为1.5-3.0倍模型桩直径。
进一步的，圆形套筒***软黏土中后将圆形套筒内部的软黏土取出，并填入砂石等散体排水材料，随后将圆形套筒从软黏土层中取出。
进一步的，将模型桩压入到砂石等散体排水材料中，且模型桩***到散体排水材料中心位置，使砂石等散体排水材料均匀分布在模型桩周围。
进一步的，散体排水材料的渗透系数是软黏土层的渗透系数的10 4-10 5倍。
进一步的，模型桩的桩端闭口且桩端呈锥形，锥角为30-60度。
进一步的，加载电机的极限加载值为200kN，行程为100mm，加载电机直接对模型桩桩顶进行加载。
本发明还提供一种上述模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置的试验方法，包括如下步骤：
在模型箱内填筑软黏土层，首先需要使软黏土的含水率达到1.5倍液限含水率，并将软黏土充分搅拌均匀，随后将软黏土填筑到模型箱中；软黏土层填筑过程中，在模型桩桩端位置以下不同深度处埋设土压力传感器和孔隙水压力传感器， 分别用于测量桩端土体中的土压力和孔隙水压力；在模型桩周围还设有竖直刚性管，竖直刚性管上沿不同深度固定有土压力传感器和孔隙水压力传感器以测试桩周土体中的土压力和孔隙水压力；软黏土层填筑完成后需要固结30-90天；
软黏土层固结完成后将端部开口的圆形套筒***到模型桩设计位置处，随后将圆形套筒内部软黏土取出，并填入散体排水材料，圆形套筒内部填筑满散体排水材料后将圆形套筒从软黏土层中取出，得到由散体排水材料填充而成的圆柱形空间；将模型桩***到散体排水材料中，使模型桩周围存在一层散体排水材料层；当桩端及桩周孔隙水压力传感器测得的土体中的超孔隙水压力完全消散后通过加载电机对模型桩进行加载。
与现有技术相比，本发明的有益效果是：
1.本发明在软黏土填筑并固结完成后，需要将端部开口的圆形套筒***软黏土中，并将圆形套筒内部的软黏土取出，随后在圆形套筒内部填入砂石等散体排水材料，最后将模型桩压入到散体排水材料中，可以有效模拟桩基周围填筑散体排水材料的施工工况。
2.本发明在软黏土填筑过程中在模型桩桩端以下土体中埋设土压力传感器和孔隙水压力传感器分别测试桩端土体中的土压力和孔隙水压力，可以对模型桩压入散体排水材料过程中桩端土体中的土压力和孔隙水压力变化情况进行分析与研究，同时也能够对模型桩压入到散体排水材料中后桩端土体中的超孔隙水压力消散规律进行分析与研究。
3.本发明在软黏土填筑过程中在桩周土体中埋设土压力传感器和孔隙水压力传感器分别测试桩周土体中的土压力和孔隙水压力，可以对模型桩压入散体排水材料过程中桩周土体中的土压力和孔隙水压力变化情况进行分析与研究，也能够对模型桩压入到散体排水材料中后桩周土体中的侧向土压力变化规律和超孔隙水压力变化规律进行研究，同时能够对加载过程中桩周土体中的侧向土压力变化规律进行分析与研究。
4.本发明采用加载电机对周围分布有散体排水材料的模型桩进行加载，可满足模型桩周围散体排水材料不同直径以及不同渗透系数条件下模型桩压入散体排水材料过程中的挤土效应研究，模型桩压入散体排水材料中后软黏土超孔隙水压力消散规律研究以及桩周存在散体排水材料层时模型桩的承载性能研究的试验要求。
附图说明
图1为软黏土层填筑并固结完成后将圆形套筒***软黏土中的模型装置示意图；
图2为将圆形套筒内部软黏土取出后的模型装置示意图；
图3为在圆形套筒内部填入散体排水材料且将圆形套筒从软黏土中取出后的模型装置示意图；
图4为将模型桩压入到散体排水材料中后的模型装置示意图；
图中：模型箱1、工字钢1-1、钢支座1-2、软黏土层1-3、土压力传感器1-4、孔隙水压力传感器1-5、圆形套筒内部软黏土1-6、散体排水材料1-7、模型桩1-8、竖直刚性管1-9、反力梁2、加载电机3、圆形套筒4。
具体实施方式
下面结合附图和实施例对本发明进一步说明。
如图1至图4所示为本发明的一种可模拟桩周散体排水材料不同直径以及不同渗透系数条件下预制桩施工时的挤土效应以及桩周土体中孔隙水压力完全消散后预制桩的承载特性的试验装置，该装置包括模型箱1、反力梁2、加载电机3和圆形套筒4共四个部分。
所述模型箱1为方形，由钢板焊接而成，模型箱侧面焊接工字钢1-1以增加模型箱刚度，模型箱1边长为6m，高度为4m，模型箱1底部焊接钢支座1-2；所述反力梁2焊接于模型箱1上；所述加载电机3固定于反力梁2上；所述模型箱1内部填筑软黏土层1-3，软黏土层1-3填筑前含水率需达到1.5倍液限含水率并且搅拌均匀；软黏土层1-3厚度为3m；所述软黏土层1-3填筑过程中在桩端和桩周土体内部均埋设土压力传感器1-4和孔隙水压力传感器1-5分别测量土压力和孔隙水压力；桩端土体中的土压力传感器和孔隙水压力传感器埋设在模型桩桩端以下0.5m，1.0m和1.5m处；桩周土体中的土压力传感器和孔隙水压力传感器均固定在竖直刚性管1-9上，土压力传感器和孔隙水压力传感器位置在软黏土表面以下0.5m，1.0m和2.0m处；所述竖直刚性管1-9刚性管直径为10mm，竖直刚性管1-9与模型桩的水平距离为1倍模型桩桩身直径和2倍模型桩桩身直径；软黏土层1-3填筑并固结完成后在设计模型桩位置处***端部开口的圆形套筒4；所述圆形套筒4与模型箱边缘的距离都为3m；所述圆形套筒4为空心钢管，外径为根据试验要求在150mm-300mm之间，长度为2200mm；在圆形套筒4内部的软黏土1-6取出后，将所述砂石等散体排水材料1-7填入圆形套筒4内部空间中；在所述砂石等散体排水材料1-7内部压入模型桩1-8；所述模型桩1-8的直径为100mm，长度为2000mm。
本发明的工作过程如下：首先需要在模型箱1内填筑软黏土层1-3，软黏土层填筑前含水率需达到1.5倍液限含水率并且搅拌均匀，软黏土层填筑完成后需等待30天使软黏土层进行固结；软黏土层1-3填筑过程中在桩端和桩周土体内部均埋设土压力传感器和孔隙水压力传感器分别测量土压力和孔隙水压力，桩周土体中的土压力传感器和孔隙水压力传感器均固定在竖直刚性管上；软黏土层 1-3填筑并固结完成后在设计位置处***端部开口的圆形套筒4，将圆形套筒内部软黏土1-6取出，随后将砂石等散体排水材料1-7填筑到圆形套筒4内部空间中；将圆形套筒从软黏土层中取出，随后将模型桩压入到散体排水材料中，且模型桩中心与散体排水材料中心一致；当桩端和桩周土体内部埋设的孔隙水压力传感器测得的软黏土中超孔隙水压力完全消散后，通过加载电机3对模型桩1-8进行加载，加载电机3所施加荷载及位移可自动读取和储存；模型桩1-8压入到散体排水材料1-7过程中桩周及桩端土体中的土压力和孔隙水压力，模型桩压入到散体排水材料中后软黏土中的孔隙水压力，模型桩加载过程中桩周及桩端土体中的土压力和孔隙水压力以及模型桩的桩顶荷载位移关系、桩端荷载位移关系以及桩土相对位移关系都可以在试验中测得。

Claims (10)

  1. 一种模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置，其特征在于：包括模型箱(1)、反力梁(2)、加载电机(3)和圆形套筒(4)；所述模型箱(1)由钢板焊接而成，模型箱(1)的侧面焊接工字钢(1-1)，底部焊接钢支座(1-2)；所述反力梁(2)焊接于模型箱(1)上；所述加载电机(3)固定于反力梁(2)上；
    所述模型箱(1)内部填筑有软黏土层(1-3)；所述软黏土层(1-3)内的桩端和桩周土体内部均埋设有土压力传感器(1-4)和孔隙水压力传感器(1-5)，分别用于测量土压力和孔隙水压力；所述的软黏土层(1-3)内设有由散体排水材料(1-7)填充而成的圆柱形空间，该圆柱形空间用于压入模型桩(1-8)，使所述的模型桩(1-8)周围均匀分布有散体排水材料(1-7)。
  2. 根据权利要求1所述的模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置，其特征在于，所述的模型箱(1)侧壁与所述的圆柱形空间之间的距离至少为该圆柱形空间截面直径的10倍。
  3. 根据权利要求1所述的模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置，其特征在于，在所述的软黏土层(1-3)填筑前，软黏土的含水率至少需达到1倍液限含水率，且为搅拌均匀的软黏土。
  4. 根据权利要求1所述的模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置，其特征在于，所述的软黏土层(1-3)的固结时间为30-90天。
  5. 根据权利要求1所述的模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置，其特征在于，模型桩(1-8)桩端位置以下不同深度处设有若干测量桩端土体中土压力的土压力传感器和测量孔隙水压力的孔隙水压力传感器，模型桩(1-8)周围不同深度处设有若干测量桩周土体中土压力的土压力传感器和测量桩周土体中孔隙水压力的孔隙水压力传感器。
  6. 根据权利要求1所述的模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置，其特征在于，所述的圆柱形空间的截面直径为模型桩(1-8)直径的1.5-3.0倍。
  7. 根据权利要求1所述的模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置，其特征在于，散体排水材料(1-7)的渗透系数是软黏土层(1-3)的渗透系数的10 4-10 5倍。
  8. 根据权利要求1所述的模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置，其特征在于，模型桩(1-8)的桩端闭口且桩端呈锥形，锥角为30-60度。
  9. 根据权利要求1所述的模拟周围填筑有散体排水材料的预制桩的桩基承 载性能的试验装置，其特征在于，加载电机(3)的极限加载值为200kN，行程为100mm。
  10. 如权利要求1-9任一项所述的模拟周围填筑有散体排水材料的预制桩的桩基承载性能的试验装置的试验方法，其特征在于，包括如下步骤：
    在模型箱(1)内填筑软黏土层(1-3)，首先需要使软黏土的含水率达到1.5倍液限含水率，并将软黏土充分搅拌均匀，随后将软黏土填筑到模型箱(1)中；软黏土层(1-3)填筑过程中，在模型桩(1-8)桩端位置以下不同深度处埋设土压力传感器(1-4)和孔隙水压力传感器(1-5)，分别用于测量桩端土体中的土压力和孔隙水压力；在模型桩(1-8)周围不同距离处还设有竖直刚性管(1-9)，竖直刚性管(1-9)上沿不同深度固定有土压力传感器(1-4)和孔隙水压力传感器(1-5)以测试桩周土体中的土压力和孔隙水压力；软黏土层填筑完成后固结30-90天；
    软黏土层(1-3)固结完成后将端部开口的圆形套筒(4)***到模型桩(1-8)设计位置处，随后将圆形套筒内部软黏土(1-6)取出，并填入散体排水材料(1-7)，圆形套筒(4)内部填筑满散体排水材料(1-7)后将圆形套筒(4)从软黏土层(1-3)中取出，得到由散体排水材料(1-7)填充而成的圆柱形空间；将模型桩(1-8)***到散体排水材料(1-7)中，使模型桩(1-8)周围存在一层散体排水材料层；当桩端及桩周孔隙水压力传感器(1-5)测得的土体中的超孔隙水压力完全消散后通过加载电机(3)对模型桩(1-8)进行加载。
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